Newpher Thomas M, Lemmon Sandra K
Department of Molecular Biology and Microbiology, Case Western Reserve University, Cleveland, OH 44106, USA.
Traffic. 2006 May;7(5):574-88. doi: 10.1111/j.1600-0854.2006.00410.x.
Clathrin is a major vesicle coat protein involved in receptor-mediated endocytosis. In yeast and higher eukaryotes, clathrin is recruited to the plasma membrane during the early stage of endocytosis along with clathrin-associated adaptors. As coated pits undergo maturation, a burst of actin polymerization accompanies and helps drive vesicle internalization. Here, we investigate the dynamics of clathrin relative to the early endocytic patch protein Sla2p. We find that clathrin is recruited to the cortex prior to Sla2p. In the absence of clathrin, normal numbers of Sla2p patches form, but many do not internalize or are dramatically delayed in completion of endocytosis. Patches that do internalize receive Sla1p late, which is followed by Abp1, which appears near the end of Sla2p lifetime. In addition, clathrin mutants develop actin comet tails, suggesting an important function in actin patch organization/dynamics. Similar to its mammalian counterparts, the light chain (LC) subunit of yeast clathrin interacts directly with the coiled-coil domain of Sla2p. A mutant of Sla2p that no longer interacts with LC (sla2Delta376-573) results in delayed progression of endocytic patches and aberrant actin dynamics. These data demonstrate an important role for clathrin in organization and progression of early endocytic patches to the late stages of endocytosis.
网格蛋白是一种主要的囊泡包被蛋白，参与受体介导的内吞作用。在酵母和高等真核生物中，网格蛋白在胞吞作用早期与网格蛋白相关衔接蛋白一起被募集到质膜上。随着包被小窝的成熟，一阵肌动蛋白聚合反应随之发生，并有助于驱动囊泡内化。在此，我们研究了网格蛋白相对于早期内吞斑蛋白Sla2p的动力学。我们发现，网格蛋白在Sla2p之前被募集到皮质。在没有网格蛋白的情况下，会形成正常数量的Sla2p斑，但许多斑不会内化，或者在胞吞作用完成时会显著延迟。确实内化的斑会很晚才接收Sla1p，随后是Abp1，它在Sla2p寿命接近尾声时出现。此外，网格蛋白突变体形成肌动蛋白彗星尾，表明其在肌动蛋白斑的组织/动力学中具有重要功能。与其哺乳动物对应物相似，酵母网格蛋白的轻链（LC）亚基直接与Sla2p的卷曲螺旋结构域相互作用。一个不再与LC相互作用的Sla2p突变体（sla2Delta376 - 573）导致内吞斑进展延迟和异常的肌动蛋白动力学。这些数据表明网格蛋白在早期内吞斑的组织以及向胞吞作用后期进展过程中发挥重要作用。
