Graduate School of Agricultural and Life Sciences, The University of Tokyo, 113-8657 Tokyo, Japan.
Division of Cellular Dynamics, National Institute for Basic Biology, 444-8585 Okazaki, Japan.
Proc Natl Acad Sci U S A. 2020 Oct 6;117(40):25150-25158. doi: 10.1073/pnas.2011152117. Epub 2020 Sep 23.
The plasma membrane (PM) acts as the interface between intra- and extracellular environments and exhibits a tightly regulated molecular composition. The composition and amount of PM proteins are regulated by balancing endocytic and exocytic trafficking in a cargo-specific manner, according to the demands of specific cellular states and developmental processes. In plant cells, retrieval of membrane proteins from the PM depends largely on clathrin-mediated endocytosis (CME). However, the mechanisms for sorting PM proteins during CME remain ambiguous. In this study, we identified a homologous pair of ANTH domain-containing proteins, PICALM1a and PICALM1b, as adaptor proteins for CME of the secretory vesicle-associated longin-type R-SNARE VAMP72 group. PICALM1 interacted with the SNARE domain of VAMP72 and clathrin at the PM. The loss of function of PICALM1 resulted in faulty retrieval of VAMP72, whereas general endocytosis was not considerably affected by this mutation. The double mutant of exhibited impaired vegetative development, indicating the requirement of VAMP72 recycling for normal plant growth. In the mammalian system, VAMP7, which is homologous to plant VAMP72, is retrieved from the PM via the interaction with a clathrin adaptor HIV Rev-binding protein in the longin domain during CME, which is not functional in the plant system, whereas retrieval of brevin-type R-SNARE members is dependent on a PICALM1 homolog. These results indicate that ANTH domain-containing proteins have evolved to be recruited distinctly for recycling R-SNARE proteins and are critical to eukaryote physiology.
质膜（PM）作为细胞内外环境的界面，表现出严格调控的分子组成。PM 蛋白的组成和数量通过以货物特异性的方式平衡内吞和外排运输来调节，根据特定细胞状态和发育过程的需求。在植物细胞中，质膜蛋白的回收在很大程度上依赖于网格蛋白介导的内吞作用（CME）。然而，CME 期间 PM 蛋白分选的机制仍不清楚。在本研究中，我们鉴定了一对同源的 ANTH 结构域蛋白 PICALM1a 和 PICALM1b，作为分泌囊泡相关长型 R-SNARE VAMP72 组 CME 的衔接蛋白。PICALM1 与 VAMP72 的 SNARE 结构域和 PM 上的网格蛋白相互作用。PICALM1 功能丧失导致 VAMP72 回收出现故障，而这种突变对一般内吞作用没有显著影响。表现出的双突变体表现出植物生长发育不良，表明 VAMP72 循环再利用是植物正常生长所必需的。在哺乳动物系统中，与植物 VAMP72 同源的 VAMP7 通过 CME 过程中长型域中网格蛋白衔接蛋白 HIV Rev 结合蛋白的相互作用从 PM 中回收，而在植物系统中该功能不起作用，而 brevin 型 R-SNARE 成员的回收依赖于 PICALM1 同源物。这些结果表明，含有 ANTH 结构域的蛋白质已经进化为专门回收 R-SNARE 蛋白，并对真核生物生理学至关重要。
