Structural and functional properties of the N- and C-terminal segments of the P4-ATPase phospholipid flippase ATP8A2.

ATP8A2 is a P4-ATPase that actively flips phosphatidylserine and to a lesser extent phosphatidylethanolamine across cell membranes to generate and maintain transmembrane phospholipid asymmetry. The importance of this flippase is evident in the finding that loss-of-function mutations in ATP8A2 are known to cause the neurodevelopmental disease known as cerebellar ataxia, intellectual disability, and dysequilibrium syndrome 4 (CAMRQ4) in humans and related neurodegenerative disorders in mice. Although significant progress has been made in understanding mechanisms underlying phospholipid binding and transport across the membrane domain, little is known about the structural and functional properties of the cytosolic N- and C-terminal segments of this flippase.

Funding priorities and health outcomes in Danish medical research.

External research funding is an essential component of the infrastructure of modern, academic research. Priorities in funding decisions drive what knowledge is generated, and how scientists' careers are shaped. For health research, it can ultimately have implications for health outcomes.

Is something rotten in the state of Denmark? Cross-national evidence for widespread involvement but not systematic use of questionable research practices across all fields of research.

Questionable research practices (QRP) are believed to be widespread, but empirical assessments are generally restricted to a few types of practices. Furthermore, conceptual confusion is rife with use and prevalence of QRPs often being confused as the same quantity. We present the hitherto most comprehensive study examining QRPs across scholarly fields and knowledge production modes.

Functional and in silico analysis of ATP8A2 and other P4-ATPase variants associated with human genetic diseases.

P4-ATPases flip lipids from the exoplasmic to cytoplasmic leaflet of cell membranes, a property crucial for many biological processes. Mutations in P4-ATPases are associated with severe inherited and complex human disorders. We determined the expression, localization and ATPase activity of four variants of ATP8A2, the P4-ATPase associated with the neurodevelopmental disorder known as cerebellar ataxia, impaired intellectual development and disequilibrium syndrome 4 (CAMRQ4).

Na,K-ATPase with Disrupted Na Binding Sites I and III Binds Na with Increased Affinity at Site II and Undergoes Na-Activated Phosphorylation with ATP.

Na,K-ATPase actively extrudes three cytoplasmic Na ions in exchange for two extracellular K ions for each ATP hydrolyzed. The atomic structure with bound Na identifies three Na sites, named I, II, and III. It has been proposed that site III is the first to be occupied and site II last, when Na binds from the cytoplasmic side.

On the track of the lipid transport pathway of the phospholipid flippase ATP8A2 - Mutation analysis of residues of the transmembrane segments M1, M2, M3 and M4.

P4-ATPases, also known as flippases, translocate specific lipids from the exoplasmic leaflet to the cytoplasmic leaflet of biological membranes, thereby generating an asymmetric lipid distribution essential for numerous cellular functions. A debated issue is which pathway within the protein the lipid substrate follows during the translocation. Here we present a comprehensive mutational screening of all amino acid residues in the transmembrane segments M1, M2, M3, and M4 of the flippase ATP8A2, thus allowing the functionally important residues in these transmembrane segments to be highlighted on a background of less important residues.

Electrogenic reaction step and phospholipid translocation pathway of the mammalian P4-ATPase ATP8A2.

ATP8A2 is a mammalian P4-ATPase (flippase) that translocates the negatively charged lipid substrate phosphatidylserine from the exoplasmic leaflet to the cytoplasmic leaflet of cellular membranes. Using an electrophysiological method based on solid supported membranes, we investigated the electrogenicity of specific reaction steps of ATP8A2 and explored a potential phospholipid translocation pathway involving residues with positively charged side chains. Changes to the current signals caused by mutations show that the main electrogenic event occurs in connection with the release of the bound phosphatidylserine to the cytoplasmic leaflet and support the hypothesis that the phospholipid interacts with specific lysine and arginine residues near the cytoplasmic border of the lipid bilayer during the translocation and reorientation required for insertion into the cytoplasmic leaflet.

Author-level data confirm the widening gender gap in publishing rates during COVID-19.

Publications are essential for a successful academic career, and there is evidence that the COVID-19 pandemic has amplified existing gender disparities in the publishing process. We used longitudinal publication data on 431,207 authors in four disciplines - basic medicine, biology, chemistry and clinical medicine - to quantify the differential impact of COVID-19 on the annual publishing rates of men and women. In a difference-in-differences analysis, we estimated that the average gender difference in publication productivity increased from -0.

Lack of consideration of sex and gender in COVID-19 clinical studies.

Sex and gender differences impact the incidence of SARS-CoV-2 infection and COVID-19 mortality. Furthermore, sex differences influence the frequency and severity of pharmacological side effects. A large number of clinical trials to develop new therapeutic approaches and vaccines for COVID-19 are ongoing.

Weak evidence of country- and institution-related status bias in the peer review of abstracts.

Research suggests that scientists based at prestigious institutions receive more credit for their work than scientists based at less prestigious institutions, as do scientists working in certain countries. We examined the extent to which country- and institution-related status signals drive such differences in scientific recognition. In a preregistered survey experiment, we asked 4,147 scientists from six disciplines (astronomy, cardiology, materials science, political science, psychology and public health) to rate abstracts that varied on two factors: (i) author country (high status vs lower status in science); (ii) author institution (high status vs lower status university).

Global citation inequality is on the rise.

Citations are important building blocks for status and success in science. We used a linked dataset of more than 4 million authors and 26 million scientific papers to quantify trends in cumulative citation inequality and concentration at the author level. Our analysis, which spans 15 y and 118 scientific disciplines, suggests that a small stratum of elite scientists accrues increasing citation shares and that citation inequality is on the rise across the natural sciences, medical sciences, and agricultural sciences.

The SERCA residue Glu340 mediates interdomain communication that guides Ca transport.

The sarco(endo)plasmic reticulum Ca-ATPase (SERCA) is a P-type ATPase that transports Ca from the cytosol into the sarco(endo)plasmic reticulum (SR/ER) lumen, driven by ATP. This primary transport activity depends on tight coupling between movements of the transmembrane helices forming the two Ca-binding sites and the cytosolic headpiece mediating ATP hydrolysis. We have addressed the molecular basis for this intramolecular communication by analyzing the structure and functional properties of the SERCA mutant E340A.

COVID-19 medical papers have fewer women first authors than expected.

The COVID-19 pandemic has resulted in school closures and distancing requirements that have disrupted both work and family life for many. Concerns exist that these disruptions caused by the pandemic may not have influenced men and women researchers equally. Many medical journals have published papers on the pandemic, which were generated by researchers facing the challenges of these disruptions.

Distinct effects of Q925 mutation on intracellular and extracellular Na and K binding to the Na, K-ATPase.

Three Na sites are defined in the Na-bound crystal structure of Na, K-ATPase. Sites I and II overlap with two K sites in the K-bound structure, whereas site III is unique and Na specific. A glutamine in transmembrane helix M8 (Q925) appears from the crystal structures to coordinate Na at site III, but does not contribute to K coordination at sites I and II.

Phosphatidylserine flipping by the P4-ATPase ATP8A2 is electrogenic.

Phospholipid flippases (P4-ATPases) utilize ATP to translocate specific phospholipids from the exoplasmic leaflet to the cytoplasmic leaflet of biological membranes, thus generating and maintaining transmembrane lipid asymmetry essential for a variety of cellular processes. P4-ATPases belong to the P-type ATPase protein family, which also encompasses the ion transporting P2-ATPases: Ca-ATPase, Na,K-ATPase, and H,K-ATPase. In comparison with the P2-ATPases, understanding of P4-ATPases is still very limited.

Gender variations in citation distributions in medicine are very small and due to self-citation and journal prestige.

A number of studies suggest that scientific papers with women in leading-author positions attract fewer citations than those with men in leading-author positions. We report the results of a matched case-control study of 1,269,542 papers in selected areas of medicine published between 2008 and 2014. We find that papers with female authors are, on average, cited between 6.

Identification and functional analyses of disease-associated P4-ATPase phospholipid flippase variants in red blood cells.

ATP-dependent phospholipid flippase activity crucial for generating lipid asymmetry was first detected in red blood cell (RBC) membranes, but the P4-ATPases responsible have not been directly determined. Using affinity-based MS, we show that ATP11C is the only abundant P4-ATPase phospholipid flippase in human RBCs, whereas ATP11C and ATP8A1 are the major P4-ATPases in mouse RBCs. We also found that ATP11A and ATP11B are present at low levels.

Asparagine 905 of the mammalian phospholipid flippase ATP8A2 is essential for lipid substrate-induced activation of ATP8A2 dephosphorylation.

The P-type ATPase protein family includes, in addition to ion pumps such as Ca-ATPase and Na,K-ATPase, also phospholipid flippases that transfer phospholipids between membrane leaflets. P-type ATPase ion pumps translocate their substrates occluded between helices in the center of the transmembrane part of the protein. The large size of the lipid substrate has stimulated speculation that flippases use a different transport mechanism.

Alpha-synuclein aggregates activate calcium pump SERCA leading to calcium dysregulation.

Aggregation of α-synuclein is a hallmark of Parkinson's disease and dementia with Lewy bodies. We here investigate the relationship between cytosolic Ca and α-synuclein aggregation. Analyses of cell lines and primary culture models of α-synuclein cytopathology reveal an early phase with reduced cytosolic Ca levels followed by a later Ca increase.

A Darier disease mutation relieves kinetic constraints imposed by the tail of sarco(endo)plasmic reticulum Ca-ATPase 2b.

The sarco(endo)plasmic reticulum Ca-ATPase (SERCA) 2b isoform possesses an extended C terminus (SERCA2b tail) forming an 11th transmembrane (TM) helix, which slows conformational changes of the Ca-pump reaction cycle. Here, we report that a Darier disease (DD) mutation of SERCA2b that changes a glutamate to a lysine in the cytoplasmic loop between TM8 and TM9 (E917K) relieves these kinetic constraints. We analyzed the effects of this mutation on the overall reaction and the individual partial reactions of the Ca pump compared with the corresponding mutations of the SERCA2a and SERCA1a isoforms, lacking the SERCA2b tail.

One and a half million medical papers reveal a link between author gender and attention to gender and sex analysis.

Gender and sex analysis is increasingly recognized as a key factor in creating better medical research and health care . Using a sample of more than 1.5 million medical research papers, our study examined the potential link between women's participation in medical science and attention to gender-related and sex-related factors in disease-specific research.

Crystal Structure of the Vanadate-Inhibited Ca(2+)-ATPase.

Vanadate is the hallmark inhibitor of the P-type ATPase family; however, structural details of its inhibitory mechanism have remained unresolved. We have determined the crystal structure of sarcoplasmic reticulum Ca(2+)-ATPase with bound vanadate in the absence of Ca(2+). Vanadate is bound at the catalytic site as a planar VO3(-) in complex with water and Mg(2+) in a dephosphorylation transition-state-like conformation.

Rescue of defective ATP8B1 trafficking by CFTR correctors as a therapeutic strategy for familial intrahepatic cholestasis.

Background & Aims: ATP8B1 deficiency is an autosomal recessive liver disease characterized by intrahepatic cholestasis. ATP8B1 mutation p.I661T, the most frequent mutation in European patients, results in protein misfolding and impaired targeting to the plasma membrane.

Determination of the ATP Affinity of the Sarcoplasmic Reticulum Ca(2+)-ATPase by Competitive Inhibition of [γ-(32)P]TNP-8N3-ATP Photolabeling.

The photoactivation of aryl azides is commonly employed as a means to covalently attach cross-linking and labeling reagents to proteins, facilitated by the high reactivity of the resultant aryl nitrenes with amino groups present in the protein side chains. We have developed a simple and reliable assay for the determination of the ATP binding affinity of native or recombinant sarcoplasmic reticulum Ca(2+)-ATPase, taking advantage of the specific photolabeling of Lys(492) in the Ca(2+)-ATPase by [γ-(32)P]2',3'-O-(2,4,6-trinitrophenyl)-8-azido-adenosine 5'-triphosphate ([γ-(32)P]TNP-8N3-ATP) and the competitive inhibition by ATP of the photolabeling reaction. The method allows determination of the ATP affinity of Ca(2+)-ATPase mutants expressed in mammalian cell culture in amounts too minute for conventional equilibrium binding studies.