Mohamad Navab
Jun 1, 2004; 45:993-1007
Thematic Reviews

Weerapan Khovidhunkit
Jul 1, 2004; 45:1169-1196
Thematic Reviews

IJ Goldberg
Apr 1, 1996; 37:693-707
Reviews

Saverio Cinti
Nov 1, 2005; 46:2347-2355
Research Articles

New Chatham House History Examines our Defining Moments News Release NCapeling 18 January 2021

'A History of Chatham House: its People and Influence from the 1920s to the 2020s' will examine the impact on policymaking of our first 100 years.

Battle lines being drawn over online freedoms in Asia Expert comment NCapeling 22 March 2021

Social media giants are increasingly clashing with Asian governments over free expression and censorship as the region lurches towards digital authoritarianism.

Freedom of expression was subject to significant restrictions in Asia even before the pandemic, with several governments having enacted laws that stifle online debate. But since COVID-19, restrictions have increased even further due to a rash of so-called ‘emergency measures’ introduced by governments across the region.

Bangladesh, India, Indonesia, Malaysia, Myanmar, Nepal, Pakistan, the Philippines, Sri Lanka, Thailand, and Vietnam have all put new laws into place, and many restrictions are already being applied in a draconian fashion, such as in the Philippines and Bangladesh.

As outlined in a new Chatham House research paper, one inspiration behind this trend is China, home to the world’s most sophisticated and restrictive system of internet control. The Chinese government’s restrictive online regime, which has tightened further under COVID-19, relies on a combination of legal regulations, technical controls, and proactive manipulation of online debates.

This model was an inspiration for Vietnam’s cybersecurity law, as well as Myanmar’s new draft cybersecurity bill, proposed by the Military-run State Administration Council in the wake of the military coup last month, which would give the military there extensive powers to access individuals’ data, restrict, or suspend access to the internet.

This ‘sovereignty and control’ model of internet governance is also gaining impetus through China’s ‘Digital Silk Road’ initiative, under which the Chinese government is exporting both its technology – such as through the establishment of smart cities, the installation of AI, and surveillance technology – and its vision of how the internet should be governed.

In November 2020, Xi Jinping pledged to further deepen cooperation with ASEAN through the Digital Silk Road, and the pandemic has expanded the appeal of Chinese surveillance technologies and data collection platforms to governments both in Asia and beyond. China’s Health Silk Road, which aims to promote global health cooperation, is centered on the Chinese government’s high-tech model under which civic freedoms are sacrificed in the name of public health.

An alternative model

This ‘sovereignty and control’ model is increasingly at odds with the more ‘human-centric’ model of tech governance favoured by many democratic states, Western social media companies, and international institutions, especially the United Nations (UN) and European Union (EU).

Although this emerging model also involves regulation, it is regulation which aims to be inclusive, risk-based, and proportionate – balancing the need for protection against online harms with the need to preserve freedom of expression. It is a multi-stakeholder, rights-based approach which brings together not just governments but also representatives of the private sector, civil society, and academia. The EU’s draft Digital Services Act and the UK’s proposals for an Online Safety Bill are both reflective of this approach.

Western social media giants such as Facebook and Twitter have recently introduced new policies which seek to identify and mitigate online harms, such as hate speech and disinformation. Industry bodies such as the Global Network Initiative, independent oversight bodies such as the Oversight Board established by Facebook, and civil society advocacy and initiatives such as the Santa Clara Principles on Transparency and Accountability in Content Moderation are also an important part of the picture.

Admittedly, these various digital governance initiatives are in some cases embryonic, and are by no means a silver bullet solution to the complex problem of online content moderation, which continues to be hotly debated in democratic societies. But they are at least underpinned by the same philosophy – that international human rights law standards must continue to apply even during emergencies such as COVID-19. With the Biden administration in the US prioritizing tech governance in its policy agenda, there is added momentum to the international leadership behind this model.

A clash of ideology

These conflicting philosophies are playing out in debates on technology governance at the UN, with one group of countries led by China and Russia advocating for greater government control of the internet, and many Western democracies emphasizing the need for an open, global internet that protects human rights.

These differing ideologies are also creating tensions between Western social media companies operating in Asia and the various governments in that region which have increased restrictions on online expression. And the gulf between the two appears to be widening.

In 2017, the Thailand government threatened Facebook with legal action unless it agreed to remove content critical of Thailand’s royal family and, in 2020, Facebook announced it had been ‘forced to block’ such material. Also in 2020, the Vietnam government pressured state-owned telecom companies to throttle internet traffic to Facebook, effectively restricting access to the platform, until Facebook agreed to take down content the government deemed to be anti-state.

Platforms refuse to silence legitimate criticism

However, Silicon Valley’s social media companies have also been pushing back. Facebook restricted the accounts of Myanmar’s military on the basis of ‘spreading misinformation’ in the wake of the military’s imposition of an internet shutdown that blocked access to Facebook, Twitter, and Instagram. And Twitter resisted requests by the Indian government to block accounts involved in protests by farmers.

Twitter stated that while it would block any accounts which it felt incited violence, it would not take action on accounts belonging to news media entities, journalists, activists, and politicians because it believed that would ‘violate the fundamental right to free expression under the Indian law’. The Indian government responded by fast-tracking stringent new social media regulations heavily criticized by rights groups for increasing government power over content on social media platforms, including online news.

So how can social media companies find avenues for operating in Asia and beyond without being co-opted into the lurch towards digital authoritarianism? There are no easy answers here, but collaboration is key. Cooperation between tech companies and local civil society partners can help companies better understand risks to human rights in the country concerned and how they might be mitigated. And tech companies are more effective in alliance with each other than acting on their own, such as the refusal by Facebook, Google, Telegram, and Twitter to hand over data on protestors to the Hong Kong police.

The fact that in many countries in Asia there are no alternatives to Western social media companies – unlike China, where platforms such as WeChat are part of the government’s internet control apparatus – gives the companies concerned some leverage. In February 2020, Facebook, Google, and Twitter together – through the Asia Internet Coalition – threatened to leave Pakistan in response to the government’s draconian proposals to regulate social media. Along with pressure and lawsuits from civil society, this forced the government into retreat, although the tussle over the new rules, introduced in November, continues.

At a time when illiberalism was already on the rise in Asia (including in democracies – Freedom House has just downgraded India’s status from ‘free’ to ‘partly free’), COVID-19 has made tighter state control of online freedom of expression even more attractive to many governments. As it seems increasingly unlikely that restrictions enacted under the guise of pandemic-related emergency measures will be repealed once the COVID-19 crisis ends, it is even more important that tech companies work with civil society on the ground to minimize the censorship of citizen voices.

Expert

A. Kh. Khachatryan, Kh. A. Khachatryan and A. Zh. Narimanyan
Trans. Moscow Math. Soc. 83 (), 183-200.
Abstract, references and article information

Decarbonizing Heat: A New Frontier for Technologies and Business Models 27 February 2019 — 8:15AM TO 9:45AM Anonymous (not verified) 3 December 2018 Chatham House | 10 St James's Square | London | SW1Y 4LE

Building space and water heating accounts for over 35 percent of global energy consumption - nearly double that of transport. However, there has been limited progress in decarbonizing the sector to date. International cooperation is required to ensure harmonized policies drag low carbon heating technologies down the cost curve to the extent that low carbon heating is cost competitive and affordable. The initial presentations and discussion focus on:

• Demand reduction technologies and policies that speed up transformation of the sector.
• The different challenges for energy efficiency of retrofitting as opposed to new build.
• The impact of electrification on GHG emissions and the power sector.
• The comparative role of national and city level initiatives.

The meeting concludes by looking at the challenges and risks in accelerating the transformation of heating and the lessons that can be learned from other sectors.

Duterte’s Victory Is Cry for Help From Those Left Behind in Philippines Expert comment sysadmin 12 May 2016

But large support for mainstream parties and a mature democratic system should keep the country from slipping back towards authoritarianism.

The victory of political outsider Rodrigo Duterte in the 2016 Philippines’ elections is proof that a significant minority of the country’s population feels left behind by its recent economic success and estranged from its political elite. However the results of the elections as a whole suggest that most voters opted for a continuation of the current government’s policies.

Duterte looks almost certain to be inaugurated as the next president of the Philippines on 30 June. The country’s presidential voting system – a single round, first-past-the-post election – delivered victory to a populist outsider with 39 per cent support. Two candidates advocating a continuation of the current government’s policies − the Liberal Party’s Mar Roxas and independent Grace Poe − polled a combined 45 per cent. The long-standing factionalism within Philippines elite politics split the ‘anti-Duterte’ vote.

Changing the conversation

The contrast between Duterte and Roxas could hardly be greater. Mar Roxas is the grandson of the first president of an independent Philippines, a graduate of Wharton Business School and a former investment banker in the US. Rodrigo Duterte is a political outsider with an electoral base geographically almost as far from Manila as is possible to get in the Philippines: the city of Davao on the island of Mindanao.

The story of Duterte’s victory is the story of how ‘Duterte managed to change the national conversation from poverty towards crime and corruption,’ says Marites Vitug, editor-at-large of one of the Philippines’ most popular online news sites, Rappler. In January, Duterte was running fourth in opinion polls but a strategy that positioned him as the only opponent to the Manila elite gave him victory. This is the first time a provincial official has made it to the top job.

The headline figures tell us that the Philippines’ economy has done very well under President Benigno Aquino. Between 2010 and 2014, growth averaged 6.3 per cent per year. That fell to a still-impressive 5.8 per cent last year but is expected to pick up this year and next, according to the Asian Development Bank. Growth in agriculture, however, is significantly slower and rural areas feel left behind. While economic growth is benefiting the majority, inequality is worsening and resentment rising in poor villages. The contrast between the metropolitan sophistication of the Makati district in Manila and life in faraway provinces such as Duterte’s Mindanao is widening.

Ironically the Philippines’ economic success is a part of the explanation for the defeat of the ‘mainstream’ presidential candidates. Crime and corruption may have become more important issues simply because more voters have become better off and therefore more likely to be concerned about crime and corruption than before. It’s also undeniable that Duterte has a record for getting things done. Human rights groups rightly criticize his (at best) tolerance of the extra-judicial killing of alleged criminals but his repeated re-election as mayor demonstrates that many citizens are prepared to accept that in exchange for improved personal security. A surprising number of Manila residents have actually moved to Davao because of its better quality of life.

Traditional power bases

However, the results as a whole suggest a narrow majority in favour of current policies. In the vice-presidential race, the Liberal Party candidate Leni Robredo is narrowly ahead of Ferdinand ‘Bongbong’ Marcos, the son of the eponymous former president. Like Duterte she is regarded as a successful mayor of a well-run city, Albay. Duterte’s running mate Alan Cayetano received just 14 per cent of the vote.

In the senate election, Liberals won five of the 12 seats being contested, with a party- backed independent winning a sixth. The opposition, even with boxing champion and national idol Manny Pacquiao running for the United Nationalist Alliance, won four.

Taken as a whole, the results show the enduring nature of traditional Philippines power bases. The country’s many islands and distinct linguistic and cultural regions are virtual fiefs in which families and big bosses can wield almost total power through control of local authorities, businesses, the courts and security forces.

Threat to democracy?

It’s easy to forget that the election of Ferdinand Marcos in 1965 was originally welcomed as a challenge to the traditional elites of Philippine politics. The same accolades are currently greeting Duterte. Could they presage a return to the Philippines’ bad old days?

This seems less likely. Philippine democracy has matured considerably since Marcos declared martial law in 1972. There is a substantial, and vocal, middle class with experience of mobilizing against ‘bad’ presidents. There will also be pressures from international investors and the Philippines’ treaty ally, the United States, for better governance.

The Philippines will chair the Association of Southeast Asian Nations next year. That will put Duterte in the international spotlight as host of several international meetings – including the East Asia Summit attended by, among others, the presidents of China, Russia and the US. Since his victory Duterte has promised to act with decorum in office and declared that his election campaign antics were just a ploy to attract attention. Some leaders in Southeast Asia will use his victory to buttress their arguments against allowing their people to freely vote. It’s up to Duterte to decide whether he wants to be an advertisement for – or an argument against – democracy.

To comment on this article, please contact Chatham House Feedback

Zhaonan Wang and Yingpu Deng
Math. Comp. 93 (), 2921-2942.
Abstract, references and article information

Lorin Crawford explains how he uses math to analyze interactions between genes. Your DNA (the biological instruction manual in all of your cells) contains a mind-boggling amount of information represented in roughly 20,000 genes that encode proteins, plus a similar number of genes with other functions. As the cost of analyzing an individual's DNA has plummeted, it has become possible to search the entire human genome for genetic variants that are associated with traits such as height or susceptibility to certain diseases. Sometimes, one gene has a straightforward impact on the trait. But in many cases, the effect of one gene variant depends on which variants of other genes are present, a phenomenon called "epistasis." Studying such interactions involves huge datasets encompassing the DNA of hundreds of thousands of people. Mathematically, that requires time-intensive calculations with massive matrices and a good working knowledge of statistics.

Bero Roos
Theor. Probability and Math. Statist. 111 (), 137-151.
Abstract, references and article information

Simão Correia
Proc. Amer. Math. Soc. 152 (), 5117-5136.
Abstract, references and article information

Neelarnab Raha
Proc. Amer. Math. Soc. 152 (), 5067-5081.
Abstract, references and article information

Bacterial low-copy-number plasmids require partition (par) systems to ensure their stable inheritance by daughter cells. In general, these systems consist of three components: a centromeric DNA sequence, a centromere-binding protein and a nucleotide hydrolase that polymerizes and functions as a motor. Type III systems, however, segregate plasmids using three proteins: the FtsZ/tubulin-like GTPase TubZ, the centromere-binding protein TubR and the MerR-like transcriptional regulator TubY. Although the TubZ filament is sufficient to transport the TubR-centromere complex in vitro, TubY is still necessary for the stable maintenance of the plasmid. TubY contains an N-terminal DNA-binding helix-turn-helix motif and a C-terminal coiled-coil followed by a cluster of lysine residues. This study determined the crystal structure of the C-terminal domain of TubY from the Bacillus cereus pXO1-like plasmid and showed that it forms a tetrameric parallel four-helix bundle that differs from the typical MerR family proteins with a dimeric anti-parallel coiled-coil. Biochemical analyses revealed that the C-terminal tail with the conserved lysine cluster helps TubY to stably associate with the TubR-centromere complex as well as to nonspecifically bind DNA. Furthermore, this C-terminal tail forms an amphipathic helix in the presence of lipids but must oligomerize to localize the protein to the membrane in vivo. Taken together, these data suggest that TubY is a component of the nucleoprotein complex within the partitioning machinery, and that lipid membranes act as mediators of type III systems.

6 July 2020

8 July 2020

Climbing out of the Chinese debt trap The World Today mhiggins.drupal 1 August 2022

Beijing must play a pivotal role in soothing African economic distress, says Alex Vines.

Poorer countries across the world – including many in Africa – are facing $35 billion in debt-service payments in 2022. According to the World Bank, around 40 per cent of this total is owed to China.

Across the African continent, the economic impacts of the coronavirus pandemic have increased rates of extreme poverty and inequality. Since early 2022 the situation has worsened even further, due to the knock-on effects of spiking inflation and interest rates following the Russian invasion of Ukraine. Shortages of fuel and foodstuffs have caused prices to leap upwards. Urban unrest is on the rise, and African governments are having to make tough economic choices as their budgets are squeezed ever more tightly.

Across the continent, progress on the UN’s Sustainable Development Goals is being jeopardized, and non-energy-producing lower and lower-middle income African governments are struggling to repay their loans.

During the Covid pandemic, the G20 assisted 31 out of 36 eligible African countries with its Debt Service Suspension Initiative (DSSI). Established in May 2020, the DSSI helped countries concentrate their resources on fighting the pandemic and safeguarding the lives and livelihoods of millions of the most vulnerable people before it expired at the end of 2021. From 2022, it has been replaced by the G20’s Common Framework for Debt Treatments.

As the second-largest economy in the world after the United States, and the dominant lender for many African states, China has an important role to play in such initiatives. Beijing still tries to keep a low profile and renegotiate its terms on a bilateral basis – although it did support Angola’s early call for G20 action on an initiative that would fulfil what the DSSI delivered. The challenge is to encourage more consistency and trust in such initiatives, as Chinese officials consider them to be too western-oriented. 
 

China’s lending to Africa peaked in 2016

Contemporary views of Chinese lending in Africa remain coloured by the rapid expansion of Chinese finance from the early 2000s to resource-rich African states, and oil producers in particular. The reality is that much of China’s lending has evolved, and is neither intrinsically predatory nor problematic for African partners – and China increasingly prefers to do business with states it considers to be better run.

In fact, as commodity prices and growth rates declined from 2015, Chinese lending to Africa fell significantly, from a peak of $29.5 billion in 2016 to $7.6 billion in 2019. The socio-economic impact of the pandemic has made this situation worse.

That China has attracted criticism is often due to a lack of transparency in its investments, especially those in Kenya and Zambia. This reputation has not been helped by opaque lending arrangements imposed by Chinese state-owned banks, requiring borrowers to prioritize them for repayment. This could lead to cutbacks in key areas of social spending, with direct impacts on African communities.

Over the past two decades, Chinese finance has contributed to an infrastructure boom in many African countries. Angola, for example, was able to undertake a rapid post-conflict reconstruction of its infrastructure, with new roads and bridges being built across the country. New models of financing are being developed: in Kenya, the new Nairobi expressway was constructed under a $600 million Build-Operate-Transfer model that provides for ownership to revert to the national government after a 30-year concession period.

Chinese companies have helped African countries build and upgrade over 10,000km of railway, around 100,000km of highway, 1,000 bridges and 100 ports, as well as power plants, hospitals and schools.

China’s involvement in African debt has varied considerably between countries and over time. Although in recent years this involvement has been framed in the context of the Belt and Road Initiative, it has for the most part been uncoordinated and unplanned, with credit being offered by competing lenders with links to different elements of the Chinese state.

In recent years, as reports have emerged around the poor quality of some of China’s past lending, the authorities in Beijing have sought greater control over new development lending and have imposed new sustainability requirements. At the same time, African countries have sought to diversify sources of supply for infrastructure contracts beyond China. Loans are generally now on a smaller, more manageable scale.

With the introduction of its Global Development Initiative in September 2021, there are indications that China is moving to a ‘new development paradigm’, with the emphasis on providing flows of foreign direct investment rather than loans and a focus on supporting small and medium-sized enterprises, human capital investments and green development.
 

African debt distress

A paper drawing on expertise from Chatham House’s Africa, Asia and Global Economy and Finance experts will be published before the G20 summit in Bali in November 2022. It examines seven African countries that the World Bank deemed in 2020 to be in most debt distress or at risk of debt distress because of their Chinese stock – Angola, Cameroon, Republic of Congo, Djibouti, Ethiopia, Kenya and Zambia. Two countries – Côte d’Ivoire and South Africa – have received new loans from China and are not in any distress.

The paper observes that a lack of transparency over the nature of the terms agreed by these African governments has led to intense domestic criticism and international accusations that China is seeking control over strategic assets.

In fact, in Angola and Zambia, China may have accidently fallen into its own debt trap through profligate and uncoordinated lending.

Zambia became the first pandemic-era default in 2020 and is seeking relief on $17 billion of external debt. After holding general elections in August 2022, Angola and Kenya will also seek additional debt relief, but both may also seek more funds from the private commercial market because of the slow progress of the G20’s Common Framework – something flagged as a concern by China.

All seven of the countries that are most indebted to China are actively seeking to reduce this financial reliance on Beijing in the future.

China has a pivotal role to play in finding effective solutions to these and other African countries’ debt distress. Improved coordination and cooperation between creditors in China and in other parts the world could enhance the positive impact of multilateral initiatives, such as the Common Framework, which has aimed to bring China and India to the negotiating table along with the IMF, the Paris Club group of creditor nations and private creditors.

So far, Chad, Ethiopia and Zambia are the only African countries to have signed up to the framework since its launch in 2020. Although China is suspicious of the IMF, if African states collectively encouraged Beijing to engage with the Common Framework, it could be improved so as to provide debt relief to those African countries finding it difficult to repay their loans.

On beyond “Detect and Respond” and “Secure by Design”

R. Greg Stacey
Nov 4, 2020; 0:RA120.002275v1-mcp.RA120.002275
Research

Madison T Wright
Nov 18, 2020; 0:RA120.002168v1-mcp.RA120.002168
Research

Mingkun Yang
Nov 24, 2020; 0:RA120.002144v1-mcp.RA120.002144
Research

Qin Zhang
Nov 17, 2020; 0:RA120.002325v1-mcp.RA120.002325
Research

Kailun Fang
Nov 30, 2020; 0:RA120.002081v1-mcp.RA120.002081
Research

Mouse embryonic stem cells (mESCs) display unique mechanical properties, including low cellular stiffness in contrast to differentiated cells, which are stiffer. We have previously shown that mESCs lacking the clathrin heavy chain (Cltc), an essential component for clathrin-mediated endocytosis (CME), display a loss of pluripotency and an enhanced expression of differentiation markers. However, it is not known whether physical properties such as cellular stiffness also change upon loss of Cltc, similar to what is seen in differentiated cells, and if so, how these altered properties specifically impact pluripotency. Using atomic force microscopy (AFM), we demonstrate that mESCs lacking Cltc display higher Young's modulus, indicative of greater cellular stiffness, compared with WT mESCs. The increase in stiffness was accompanied by the presence of actin stress fibers and accumulation of the inactive, phosphorylated, actin-binding protein cofilin. Treatment of Cltc knockdown mESCs with actin polymerization inhibitors resulted in a decrease in the Young's modulus to values similar to those obtained with WT mESCs. However, a rescue in the expression profile of pluripotency factors was not obtained. Additionally, whereas WT mouse embryonic fibroblasts could be reprogrammed to a state of pluripotency, this was inhibited in the absence of Cltc. This indicates that the presence of active CME is essential for the pluripotency of embryonic stem cells. Additionally, whereas physical properties may serve as a simple readout of the cellular state, they may not always faithfully recapitulate the underlying molecular fate.

Adult progenitor cell populations typically exist in a quiescent state within a controlled niche environment. However, various stresses or forms of damage can disrupt this state, which often leads to dysfunction and aging. We built a glucocorticoid (GC)-induced liver damage model of mice, found that GC stress induced liver damage, leading to consequences for progenitor cells expansion. However, the mechanisms by which niche factors cause progenitor cells proliferation are largely unknown. We demonstrate that, within the liver progenitor cells niche, Galectin-3 (Gal-3) is responsible for driving a subset of progenitor cells to break quiescence. We show that GC stress causes aging of the niche, which induces the up-regulation of Gal-3. The increased Gal-3 population increasingly interacts with the progenitor cell marker CD133, which triggers focal adhesion kinase (FAK)/AMP-activated kinase (AMPK) signaling. This results in the loss of quiescence and leads to the eventual stemness exhaustion of progenitor cells. Conversely, blocking Gal-3 with the inhibitor TD139 prevents the loss of stemness and improves liver function. These experiments identify a stress-dependent change in progenitor cell niche that directly influence liver progenitor cell quiescence and function.

Protein biosynthesis is fundamental to cellular life and requires the efficient functioning of the translational machinery. At the center of this machinery is the ribosome, a ribonucleoprotein complex that depends heavily on Mg2+ for structure. Recent work has indicated that other metal cations can substitute for Mg2+, raising questions about the role different metals may play in the maintenance of the ribosome under oxidative stress conditions. Here, we assess ribosomal integrity following oxidative stress both in vitro and in cells to elucidate details of the interactions between Fe2+ and the ribosome and identify Mn2+ as a factor capable of attenuating oxidant-induced Fe2+-mediated degradation of rRNA. We report that Fe2+ promotes degradation of all rRNA species of the yeast ribosome and that it is bound directly to RNA molecules. Furthermore, we demonstrate that Mn2+ competes with Fe2+ for rRNA-binding sites and that protection of ribosomes from Fe2+-mediated rRNA hydrolysis correlates with the restoration of cell viability. Our data, therefore, suggest a relationship between these two transition metals in controlling ribosome stability under oxidative stress.

Mutations in the GUCY2D gene coding for the dimeric human retinal membrane guanylyl cyclase (RetGC) isozyme RetGC1 cause various forms of blindness, ranging from rod dysfunction to rod and cone degeneration. We tested how the mutations causing recessive congenital stationary night blindness (CSNB), recessive Leber's congenital amaurosis (LCA1), and dominant cone–rod dystrophy-6 (CORD6) affected RetGC1 activity and regulation by RetGC-activating proteins (GCAPs) and retinal degeneration-3 protein (RD3). CSNB mutations R666W, R761W, and L911F, as well as LCA1 mutations R768W and G982VfsX39, disabled RetGC1 activation by human GCAP1, -2, and -3. The R666W and R761W substitutions compromised binding of GCAP1 with RetGC1 in HEK293 cells. In contrast, G982VfsX39 and L911F RetGC1 retained the ability to bind GCAP1 in cyto but failed to effectively bind RD3. R768W RetGC1 did not bind either GCAP1 or RD3. The co-expression of GUCY2D allelic combinations linked to CSNB did not restore RetGC1 activity in vitro. The CORD6 mutation R838S in the RetGC1 dimerization domain strongly dominated the Ca2+ sensitivity of cyclase regulation by GCAP1 in RetGC1 heterodimer produced by co-expression of WT and the R838S subunits. It required higher Ca2+ concentrations to decelerate GCAP-activated RetGC1 heterodimer—6-fold higher than WT and 2-fold higher than the Ser838-harboring homodimer. The heterodimer was also more resistant than homodimers to inhibition by RD3. The observed biochemical changes can explain the dominant CORD6 blindness and recessive LCA1 blindness, both of which affect rods and cones, but they cannot explain the selective loss of rod function in recessive CSNB.

The kinesin-3 family contains the fastest and most processive motors of the three neuronal transport kinesin families, yet the sequence of states and rates of kinetic transitions that comprise the chemomechanical cycle and give rise to their unique properties are poorly understood. We used stopped-flow fluorescence spectroscopy and single-molecule motility assays to delineate the chemomechanical cycle of the kinesin-3, KIF1A. Our bacterially expressed KIF1A construct, dimerized via a kinesin-1 coiled-coil, exhibits fast velocity and superprocessivity behavior similar to WT KIF1A. We established that the KIF1A forward step is triggered by hydrolysis of ATP and not by ATP binding, meaning that KIF1A follows the same chemomechanical cycle as established for kinesin-1 and -2. The ATP-triggered half-site release rate of KIF1A was similar to the stepping rate, indicating that during stepping, rear-head detachment is an order of magnitude faster than in kinesin-1 and kinesin-2. Thus, KIF1A spends the majority of its hydrolysis cycle in a one-head-bound state. Both the ADP off-rate and the ATP on-rate at physiological ATP concentration were fast, eliminating these steps as possible rate-limiting transitions. Based on the measured run length and the relatively slow off-rate in ADP, we conclude that attachment of the tethered head is the rate-limiting transition in the KIF1A stepping cycle. Thus, KIF1A's activity can be explained by a fast rear-head detachment rate, a rate-limiting step of tethered-head attachment that follows ATP hydrolysis, and a relatively strong electrostatic interaction with the microtubule in the weakly bound post-hydrolysis state.

Priyanka Tripathi
Dec 30, 2020; 0:jlr.RA120001190v1-jlr.RA120001190
Research Articles

Melissa Gómez
Dec 1, 2020; 61:1658-1674
Research Articles

Jiayan Guo
Dec 1, 2020; 61:1764-1775
Research Articles

In SAS Business Rules Manager 3.3, the initial loading of a rule set and a rule flow takes significantly longer than it does in release 3.2. When this problem happens, long time gaps are evident in the local

Microtubules are polymers composed of αβ-tubulin subunits that provide structure to cells and play a crucial role in in the development and function of neuronal processes and cilia, microtubule-driven extensions of the plasma membrane that have sensory (primary cilia) or motor (motile cilia) functions. To stabilize microtubules in neuronal processes and cilia, α tubulin is modified by the posttranslational addition of an acetyl group, or acetylation. We discovered that acetylated tubulin in microtubules interacts with the membrane sphingolipid, ceramide. However, the molecular mechanism and function of this interaction are not understood. Here, we show that in human iPS cell-derived neurons, ceramide stabilizes microtubules, which indicates a similar function in cilia. Using proximity ligation assays, we detected complex formation of ceramide with acetylated tubulin in C. reinhardtii flagella and cilia of human embryonic kidney (HEK293T) cells, primary cultured mouse astrocytes, and ependymal cells. Using incorporation of palmitic azide and click chemistry-mediated addition of fluorophores, we show that a portion of acetylated tubulin is S-palmitoylated. S-palmitoylated acetylated tubulin is colocalized with ceramide-rich platforms (CRPs) in the ciliary membrane, and it is coimmunoprecipitated with Arl13b, a GTPase that mediates transport of proteins into cilia. Inhibition of S-palmitoylation with 2-bromo palmitic acid or inhibition of ceramide biosynthesis with fumonisin B1 reduces formation of the Arl13b-acetylated tubulin complex and its transport into cilia, concurrent with impairment of ciliogenesis. Together, these data show, for the first time, that CRPs mediate membrane anchoring and interaction of S-palmitoylated proteins that are critical for cilium formation, stabilization, and function. 

Accompanied with nutrition transition, non-HDL-C levels of individuals in Asian countries has increased rapidly, which has caused the global epicenter of nonoptimal cholesterol to shift from Western countries to Asian countries. Thus, it is critical to underline major genetic and dietary determinants. In the current study of 2,330 Chinese individuals, genetic risk scores (GRSs) were calculated for total cholesterol (TC; GRS_TC, 57 SNPs), LDL-C (GRS_LDL-C, 45 SNPs), and HDL-C (GRS_HDL-C, 65 SNPs) based on SNPs from the Global Lipid Genetics Consortium study. Cholesterol intake was estimated by a 74-item food-frequency questionnaire. Associations of dietary cholesterol intake with plasma TC and LDL-C strengthened across quartiles of the GRS_TC (effect sizes: –0.29, 0.34, 2.45, and 6.47; P_interaction = 0.002) and GRS_LDL-C (effect sizes: –1.35, 0.17, 5.45, and 6.07; P_interaction = 0.001), respectively. Similar interactions with non-HDL-C were observed between dietary cholesterol and GRS_TC (P_interaction = 0.001) and GRS_LDL-C (P_interaction = 0.004). The adverse effects of GRS_TC on TC (effect sizes across dietary cholesterol quartiles: 0.51, 0.82, 1.21, and 1.31; P_interaction = 0.023) and GRS_LDL-C on LDL-C (effect sizes across dietary cholesterol quartiles: 0.66, 0.52, 1.12, and 1.56; P_interaction = 0.020) were more profound in those having higher cholesterol intake compared with those with lower intake. Our findings suggest significant interactions between genetic susceptibility and dietary cholesterol intake on plasma cholesterol profiles in a Chinese population.

Adaptive thermogenesis is highly dependent on uncoupling protein 1 (UCP1), a protein expressed by thermogenic adipocytes present in brown adipose tissue (BAT) and white adipose tissue (WAT). Thermogenic capacity of human and mouse BAT can be measured by positron emission tomography-computed tomography quantifying the uptake of ¹⁸F-fluodeoxyglucose or lipid tracers. BAT activation is typically studied in response to cold exposure or treatment with β-3-adrenergic receptor agonists such as CL316,243 (CL). Currently, it is unknown whether cold-stimulated uptake of glucose or lipid tracers is a good surrogate marker of UCP1-mediated thermogenesis. In metabolic studies using radiolabeled tracers, we found that glucose uptake is increased in mildly cold-activated BAT of Ucp1^–/– versus WT mice kept at subthermoneutral temperature. Conversely, lower glucose disposal was detected after full thermogenic activation achieved by sustained cold exposure or CL treatment. In contrast, uptake of lipoprotein-derived fatty acids into chronically activated thermogenic adipose tissues was substantially increased in UCP1-deficient mice. This effect is linked to higher sympathetic tone in adipose tissues of Ucp1^–/– mice, as indicated by elevated levels of thermogenic genes in BAT and WAT. Thus, glucose and lipoprotein handling does not necessarily reflect UCP1-dependent thermogenic activity, but especially lipid uptake rather mirrors sympathetic activation of adipose tissues.

Of the known regulators of atherosclerosis, miRNAs have been demonstrated to play critical roles in lipoprotein homeostasis and plaque formation. Here, we generated a novel animal model of atherosclerosis by knocking in LDLR^W483X in C57BL/6 mice, as the W483X mutation in LDLR is considered the most common newly identified pathogenic mutation in Chinese familial hypercholesterolemia (FH) individuals. Using the new in vivo mouse model combined with a well-established atherosclerotic in vitro human cell model, we identified a novel atherosclerosis-related miRNA, miR-23a-3p, by microarray analysis of mouse aortic tissue specimens and human aortic endothelial cells (HAECs). miR-23a-3p was consistently downregulated in both models, which was confirmed by qPCR. Bioinformatics analysis and further validation experiments revealed that the TNFα-induced protein 3 (TNFAIP3) gene was the key target of miR-23a-3p. The miR-23a-3p-related functional pathways were then analyzed in HAECs. Collectively, the present results suggest that miR-23a-3p regulates inflammatory and apoptotic pathways in atherogenesis by targeting TNFAIP3 through the NF-B and p38/MAPK signaling pathways.

Xanthophyllomyces dendrorhous is a basidiomycete yeast that produces carotenoids, mainly astaxanthin. Astaxanthin is an organic pigment of commercial interest due to its antioxidant and coloring properties. X. dendrorhous has a functional SREBP pathway, and the Sre1 protein is the SREBP homolog in this yeast. However, how sterol regulatory element (Sre)1 promotes the biosynthesis of sterols and carotenoids in X. dendrorhous is unknown. In this work, comparative RNA-sequencing analysis between modified X. dendrorhous strains that have an active Sre1 protein and the WT was performed to identify Sre1-dependent genes. In addition, Sre1 direct target genes were identified through ChIP combined with lambda exonuclease digestion (ChIP-exo) assays. SRE motifs were detected in the promoter regions of several Sre1 direct target genes and were consistent with the SREs described in other yeast species. Sre1 directly regulates genes related to ergosterol biosynthesis as well as genes related to the mevalonate (MVA) pathway, which synthesizes the building blocks of isoprenoids, including carotenoids. Two carotenogenic genes, crtE and crtR, were also identified as Sre1 direct target genes. Thus, carotenogenesis in X. dendrorhous is regulated by Sre1 through the regulation of the MVA pathway and the regulation of the crtE and crtR genes. As the crtR gene encodes a cytochrome P450 reductase, Sre1 regulates pathways that include cytochrome P450 enzymes, such as the biosynthesis of carotenoids and sterols. These results demonstrate that Sre1 is a sterol master regulator that is conserved in X. dendrorhous.

Voltage-gated Cav1 and Cav2 Ca2+ channels are comprised of a pore-forming α1 subunit (Cav1.1-1.4, Cav2.1-2.3) and auxiliary β (β1-4) and α2δ (α2δ−1−4) subunits. The properties of these channels vary with distinct combinations of Cav subunits and alternative splicing of the encoding transcripts. Therefore, the impact of disease-causing mutations affecting these channels may depend on the identities of Cav subunits and splice variants. Here, we analyzed the effects of a congenital stationary night blindness type 2 (CSNB2)-causing mutation, I745T (IT), in Cav1.4 channels typical of those in human retina: Cav1.4 splice variants with or without exon 47 (Cav1.4+ex47 and Cav1.4Δex47, respectively), and the auxiliary subunits, β2X13 and α2δ-4. We find that IT caused both Cav1.4 splice variants to activate at significantly more negative voltages and with slower deactivation kinetics than the corresponding WT channels. These effects of the IT mutation, along with unexpected alterations in ion selectivity, were generally larger in channels lacking exon 47. The weaker ion selectivity caused by IT led to hyperpolarizing shifts in the reversal potential and large outward currents that were evident in channels containing the auxiliary subunits β2X13 and α2δ-4 but not in those with β2A and α2δ-1. We conclude that the IT mutation stabilizes channel opening and alters ion selectivity of Cav1.4 in a manner that is strengthened by exclusion of exon 47 and inclusion of β2X13 and α2δ-4. Our results reveal complex actions of IT in modifying the properties of Cav1.4 channels, which may influence the pathological consequences of this mutation in retinal photoreceptors.