Yeast and human P4-ATPases transport glycosphingolipids using conserved structural motifs.

Lipid transport is an essential process with manifest importance to human health and disease. Phospholipid flippases (P4-ATPases) transport lipids across the membrane bilayer and are involved in signal transduction, cell division, and vesicular transport. Mutations in flippase genes cause or contribute to a host of diseases, such as cholestasis, neurological deficits, immunological dysfunction, and metabolic disorders. Genome-wide association studies have shown that ATP10A and ATP10D variants are associated with an increased risk of diabetes, obesity, myocardial infarction, and atherosclerosis. Moreover, ATP10D SNPs are associated with elevated levels of glucosylceramide (GlcCer) in plasma from diverse European populations. Although sphingolipids strongly contribute to metabolic disease, little is known about how GlcCer is transported across cell membranes. Here, we identify a conserved clade of P4-ATPases from Saccharomyces cerevisiae (Dnf1, Dnf2), Schizosaccharomyces pombe (Dnf2), and Homo sapiens (ATP10A, ATP10D) that transport GlcCer bearing an sn2 acyl-linked fluorescent tag. Further, we establish structural determinants necessary for recognition of this sphingolipid substrate. Using enzyme chimeras and site-directed mutagenesis, we observed that residues in transmembrane (TM) segments 1, 4, and 6 contribute to GlcCer selection, with a conserved glutamine in the center of TM4 playing an essential role. Our molecular observations help refine models for substrate translocation by P4-ATPases, clarify the relationship between these flippases and human disease, and have fundamental implications for membrane organization and sphingolipid homeostasis.

Emerging Causes of Drug-Induced Anaphylaxis: A Review of Anaphylaxis-Associated Reports in the FDA Adverse Event Reporting System (FAERS).

BACKGROUND: Drug-induced anaphylaxis is a well-known adverse drug reaction for some drug classes, but emerging drug causes of anaphylaxis and novel mechanisms may contribute in unrecognized ways. OBJECTIVE: We sought to determine the top drugs reported in association with anaphylaxis and anaphylaxis followed by death in the Food and Drug Administration Adverse Event Reporting System (FAERS). METHODS: We reviewed the publicly available FAERS database from 1999 to 2019. Using search terms "anaphylactic shock" or "anaphylactic reaction" and sorting cases by generic drug names, we counted and trended reports to FAERS in which a drug was associated with anaphylaxis or anaphylaxis followed by death. RESULTS: From 1999 to 2019, there were 17,506,002 adverse drug events reported in FAERS, of which 47,496 (0.27%) were reported as anaphylaxis. Excluding patients without age, sex, or country data, respectively, the median age of patients in reports of anaphylaxis was 52 (interquartile range: 28), 62.71% were female, and 13,899 of 34,381 (40.43%) reports were from the United States. There were 2984 of 47,496 (6.28%) reports of anaphylaxis followed by death. Top drug classes associated with anaphylaxis in FAERS were antibiotics, monoclonal antibodies (mAbs), nonsteroidal anti-inflammatory drugs, and acetaminophen. Top drug classes associated with anaphylaxis deaths were antibiotics, radiocontrast agents, and intraoperative agents. Linear regression demonstrated reports of anaphylaxis to mAbs increasing at an average rate of 0.77% of total anaphylaxis reports per year (95% confidence interval: 0.65, 0.88) from 2.00% in 1999 to 17.37% in 2019, faster than any other drug class. CONCLUSION: Antibiotics were highly reported for anaphylaxis overall and anaphylaxis followed by death. Increasing reports were noted for anaphylaxis to mAb therapies.