Substrate specificity controlled by the exit site of human P4-ATPases, revealed by de novo point mutations in neurological disorders

• 成果类型: Article
• 署名作者: Calianese, David C.; Noji, Tomoyasu; Sullivan, Jennifer A.; Schoch, Kelly; Shashi, Vandana; McNiven, Vanda; Ramos, Luiza Lorena Pires; Jordanova, Albena; Karteszi, Judit; Ishikita, Hiroshi; Nagata, Shigekazu
• 署名单位: University of North Carolina; University of North Carolina Chapel Hill; University of Osaka; University of Tokyo; Duke University; University of Toronto; University Health Network Toronto; McMaster University; McMaster University Hospital; Flanders Institute for Biotechnology (VIB); University of Antwerp; Medical University Sofia
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-12053
• DOI: 10.1073/pnas.2415755121
• 发表日期: 2024-10-29
• 关键词: p-type atpases; molecular-dynamics; phospholipid flippases; transport; residues; SYSTEM

摘要

The maintenance of lipid asymmetry on the plasma membrane is regulated by flippases, such as ATP8A2, ATP11A, and ATP11C, which translocate phosphatidylserine and phosphatidylethanolamine from the outer leaflet to the inner leaflet. We previously identified a patient- derived point mutation (Q84E) in ATP11A at the phospholipid entry site, which acquired the ability to flip phosphatidylcholine (PtdCho). This mutation led to elevated levels of sphingomyelin (SM) in the outer leaflet of the plasma membrane. We herein present two de novo ATP11A dominant mutations (E114G and S399L) in heterozygous patients exhibiting neurological and developmental disorders. These mutations, situated near the predicted phospholipid exit site, similarly confer the ability for ATP11A to recognize PtdCho as a substrate, resulting in its internalization into cells. Cells expressing these mutants had increased SM levels on their surface, attributed to the up- regulated expression of the sphingomyelin synthase-1 gene, rendering them more susceptible to SM phosphodiesterase- mediated cell lysis. Corresponding mutations in ATP11C and ATP8A2, paralogs of ATP11A, exerted similar effects on PtdCho- flipping activity and increased SM levels on the cell surface. Molecular dynamics simulations, based on the ATP11C structure, suggest that the E114G and S399L mutations enhance ATP11C's affinity toward PtdCho. These findings underscore the importance of the well- conserved exit and entry sites in determining phospholipid substrate specificity and indicate that aberrant flipping of PtdCho contributes to neurological disorders.