Jin Mingji, Cai Mingjie
Institute of Molecular and Cell Biology, Singapore 138673, Republic of Singapore.
Mol Biol Cell. 2008 Jan;19(1):297-307. doi: 10.1091/mbc.e07-06-0530. Epub 2007 Oct 31.
The yeast protein Pan1p plays essential roles in actin cytoskeleton organization and endocytosis. It couples endocytosis with actin polymerization through its dual function in endocytic complex assembly and activation of the actin polymerization initiation complex Arp2/3p. Phosphorylation of Pan1p and other components of the endocytic complex by the kinase Prk1p leads to disassembly of the coat complex and the termination of vesicle-associated actin polymerization. A homologous kinase, Ark1p, has also been implicated in this regulatory process. In this study, we investigated the distinct roles of Prk1p and Ark1p. We found that the nonkinase domains determined the functional specificity of the two kinases. A short region located adjacent to the kinase domain unique to Prk1p was found to be required for the kinase to interact with Arp2p. Further studies demonstrated that the Prk1p-Arp2p interaction is critical for down-regulation of Pan1p. These findings reveal that, in addition to its role in the nucleation of actin polymerization, Arp2p also mediates what appears to be an auto-regulatory mechanism possibly adapted for efficient coordination of actin assembly and disassembly during endocytosis.
酵母蛋白Pan1p在肌动蛋白细胞骨架组织和内吞作用中发挥着重要作用。它通过在内吞复合物组装和肌动蛋白聚合起始复合物Arp2/3p激活中的双重功能，将内吞作用与肌动蛋白聚合联系起来。激酶Prk1p对Pan1p和内吞复合物的其他成分进行磷酸化，导致包被复合物的解体以及与囊泡相关的肌动蛋白聚合的终止。一种同源激酶Ark1p也参与了这一调节过程。在本研究中，我们调查了Prk1p和Ark1p的不同作用。我们发现非激酶结构域决定了这两种激酶的功能特异性。我们发现，Prk1p特有的与激酶结构域相邻的一个短区域是该激酶与Arp2p相互作用所必需的。进一步的研究表明，Prk1p与Arp2p的相互作用对于Pan1p的下调至关重要。这些发现揭示，除了在肌动蛋白聚合的成核作用中发挥作用外，Arp2p还介导了一种似乎是自动调节机制，可能适用于内吞作用期间肌动蛋白组装和解聚的有效协调。
