Pishvaee B, Costaguta G, Yeung B G, Ryazantsev S, Greener T, Greene L E, Eisenberg E, McCaffery J M, Payne G S
Department of Biological Chemistry, UCLA School of Medicine, Los Angeles, California 90024, USA.
Nat Cell Biol. 2000 Dec;2(12):958-63. doi: 10.1038/35046619.
Clathrin-coated vesicles mediate diverse processes such as nutrient uptake, downregulation of hormone receptors, formation of synaptic vesicles, virus entry, and transport of biosynthetic proteins to lysosomes. Cycles of coat assembly and disassembly are integral features of clathrin-mediated vesicular transport (Fig. 1a). Coat assembly involves recruitment of clathrin triskelia, adaptor complexes and other factors that influence coat assembly, cargo sequestration, membrane invagination and scission (Fig. 1a). Coat disassembly is thought to be essential for fusion of vesicles with target membranes and for recycling components of clathrin coats to the cytoplasm for further rounds of vesicle formation. In vitro, cytosolic heat-shock protein 70 (Hsp70) and the J-domain co-chaperone auxilin catalyse coat disassembly. However, a specific function of these factors in uncoating in vivo has not been demonstrated, leaving the physiological mechanism and significance of uncoating unclear. Here we report the identification and characterization of a Saccharomyces cerevisiae J-domain protein, Aux1. Inactivation of Aux1 results in accumulation of clathrin-coated vesicles, impaired cargo delivery, and an increased ratio of vesicle-associated to cytoplasmic clathrin. Our results demonstrate an in vivo uncoating function of a J domain co-chaperone and establish the physiological significance of uncoating in transport mediated by clathrin-coated vesicles.
网格蛋白包被小泡介导多种过程，如营养物质摄取、激素受体下调、突触小泡形成、病毒进入以及生物合成蛋白向溶酶体的运输。包被的组装和解聚循环是网格蛋白介导的小泡运输的固有特征（图1a）。包被组装涉及网格蛋白三脚蛋白复合体、衔接蛋白复合体和其他影响包被组装、货物隔离、膜内陷和切割的因子的募集（图1a）。包被解聚被认为对于小泡与靶膜的融合以及将网格蛋白包被的组分循环至细胞质以进行新一轮的小泡形成至关重要。在体外，胞质热休克蛋白70（Hsp70）和J结构域共伴侣辅助蛋白催化包被解聚。然而，这些因子在体内脱包被中的特定功能尚未得到证实，使得脱包被的生理机制和意义尚不清楚。在此，我们报告了酿酒酵母J结构域蛋白Aux1的鉴定和特征。Aux1失活导致网格蛋白包被小泡积累、货物递送受损以及小泡相关网格蛋白与细胞质网格蛋白的比例增加。我们的结果证明了J结构域共伴侣在体内的脱包被功能，并确立了脱包被在网格蛋白包被小泡介导的运输中的生理意义。
