RESUMO

Clathrin- and actin-mediated endocytosis is essential in eukaryotic cells. In this study, we demonstrate that Tda2 is a novel protein of the endocytic machinery necessary for normal internalization of native cargo in yeast. Tda2 has not been classified in any protein family. Unexpectedly, solving the crystal structure of Tda2 revealed it belongs to the dynein light chain family. However, Tda2 works independently of the dynein motor complex and microtubules. Tda2 forms a tight complex with the polyproline motif-rich protein Aim21, which interacts physically with the SH3 domain of the Arp2/3 complex regulator Bbc1. The Tda2-Aim21 complex localizes to endocytic sites in a Bbc1- and filamentous actin-dependent manner. Importantly, the Tda2-Aim21 complex interacts directly with and facilitates the recruitment of actin-capping protein, revealing barbed-end filament capping at endocytic sites to be a regulated event. Thus, we have uncovered a new layer of regulation of the actin cytoskeleton by a member of a conserved protein family that has not been previously associated with a function in endocytosis.

Assuntos

Citoesqueleto de Actina/metabolismo , Actinas/metabolismo , Vesículas Revestidas por Clatrina/metabolismo , Dineínas/metabolismo , Endocitose , Proteínas de Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/metabolismo , Proteínas de Capeamento de Actina/metabolismo , Complexo 2-3 de Proteínas Relacionadas à Actina/genética , Complexo 2-3 de Proteínas Relacionadas à Actina/metabolismo , Proteínas do Citoesqueleto/genética , Proteínas do Citoesqueleto/metabolismo , Dineínas/química , Complexo de Proteínas da Cadeia de Transporte de Elétrons/genética , Complexo de Proteínas da Cadeia de Transporte de Elétrons/metabolismo , Genótipo , Cinética , Microscopia de Fluorescência , Microscopia de Vídeo , Modelos Moleculares , Mutação , Fenótipo , Ligação Proteica , Conformação Proteica , Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/química , Proteínas de Saccharomyces cerevisiae/genética , Transdução de Sinais , Relação Estrutura-Atividade