PHYLIFE: Physical Life Science, Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Odense 5230, Denmark.
Danish Cancer Institute, Copenhagen 2100, Denmark.
J Phys Chem B. 2024 Sep 12;128(36):8701-8711. doi: 10.1021/acs.jpcb.4c02318. Epub 2024 Aug 30.
Annexins (ANXAs), calcium-sensitive phospholipid-binding proteins, are pivotal for cellular membrane repair, which is crucial for eukaryotic cell survival under membrane stress. With their unique trimeric arrangements and crystalline arrays on the membrane surface, ANXA4 and ANXA5 induce membrane curvature and rapidly orchestrate plasma membrane resealing. However, the influence of cholesterol and anionic lipid headgroups on annexin-induced membrane curvature remains poorly understood at the molecular level. Using all-atom molecular dynamics simulations, we measured the local curvature-induced underneath ANXA4 and ANXA5 monomers and trimers when they bind to lipid bilayers of distinct lipid compositions: PSPC (20% POPS, 80% POPC), PAPC (20% POPA, 80% POPC), and PSPCCHL (14% POPS, 56% POPC, 30% cholesterol). Laser injury experiments were conducted on MCF7 cells transfected to transiently express fluorescently labeled ANXA4 or ANXA5 to facilitate the examination of protein and lipid accumulation at the damage site. Annexin trimers induce higher curvature than monomers, particularly with cholesterol present. Annexin trimers induce similar curvatures on both PAPC and PSPC membranes. Notably, among monomers, ANXA5 induces the highest curvature on PAPC, suggesting more efficient recruitment of ANXA5 compared with ANXA4 in the early stages of membrane repair near a lesion. Laser injury experiments confirm rapid coaccumulation of phosphatidic acid lipids with ANXA4 and ANXA5 at repair sites, potentially enhancing the accumulation of annexins in the early stages of membrane repair.
膜联蛋白（ANXAs）是一种对钙离子敏感的磷脂结合蛋白，在细胞膜修复中起着关键作用，这对于真核细胞在膜应激下的生存至关重要。膜联蛋白 4（ANXA4）和膜联蛋白 5（ANXA5）以其独特的三聚体排列和在膜表面的晶体排列，诱导膜曲率变化，并迅速协调质膜的重新封闭。然而，胆固醇和阴离子脂质头部基团对膜联蛋白诱导的膜曲率的影响在分子水平上仍知之甚少。本研究使用全原子分子动力学模拟，测量了 ANXA4 和 ANXA5 单体和三聚体与不同脂质组成的脂质双层结合时，在其下诱导的局部曲率：PSPC（20% POPS，80% POPC）、PAPC（20% POPA，80% POPC）和 PSPCCHL（14% POPS，56% POPC，30% 胆固醇）。通过激光损伤实验，对瞬时表达荧光标记的 ANXA4 或 ANXA5 的 MCF7 细胞进行转染，以方便检查损伤部位的蛋白质和脂质积累。膜联蛋白三聚体比单体诱导更高的曲率，尤其是在存在胆固醇的情况下。膜联蛋白三聚体在 PAPC 和 PSPC 膜上诱导相似的曲率。值得注意的是，在单体中，ANXA5 在 PAPC 上诱导的曲率最高，这表明在损伤附近的膜修复早期，与 ANXA4 相比，ANXA5 更有效地募集。激光损伤实验证实，在修复部位，磷脂酸脂质与 ANXA4 和 ANXA5 迅速共同积累，这可能增强了早期膜修复中膜联蛋白的积累。
