RESUMO
Recent studies have revealed the detailed timing of protein recruitment to endocytic sites in budding yeast. However, little is understood about the early stages of their formation. Here we identify the septin-associated protein Syp1p as a component of the machinery that drives clathrin-mediated endocytosis in budding yeast. Syp1p arrives at endocytic sites early in their formation and shares unique dynamics with the EH-domain protein Ede1p. We find that Syp1p is related in amino acid sequence to several mammalian proteins one of which, SGIP1-alpha, is an endocytic component that binds the Ede1p homolog Eps15. Like Syp1p, SGIP1-alpha arrives early at sites of clathrin-mediated endocytosis, suggesting that Syp1p/Ede1p and SGIP1-alpha/Eps15 may have a conserved function. In yeast, both Syp1p and Ede1p play important roles in the rate of endocytic site turnover. Additionally, Ede1p is important for endocytic site formation, whereas Syp1p acts as a polarized factor that recruits both Ede1p and endocytic sites to the necks of emerging buds. Thus Ede1p and Syp1p are conserved, early-arriving endocytic proteins with roles in the formation and placement of endocytic sites, respectively.
Assuntos
Proteínas de Transporte/metabolismo , Endocitose/fisiologia , Proteínas de Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/citologia , Sequência de Aminoácidos , Animais , Proteínas de Transporte/genética , Humanos , Dados de Sequência Molecular , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/metabolismo , Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/genética , Alinhamento de SequênciaRESUMO
Internalization of cargo by clathrin-mediated endocytosis has been studied extensively. In this issue of Cell Host & Microbe, Cossart and colleagues report that a variety of pathogens induce the recruitment of clathrin and other endocytic proteins to sites of pathogen interaction with the cell surface. This recruitment is followed by actin rearrangements in the host cell necessary for the uptake or stable attachment of the pathogen at the cell surface.
Assuntos
Infecções Bacterianas/microbiologia , Fenômenos Fisiológicos Bacterianos , Clatrina/fisiologia , Actinas/metabolismo , Animais , Bactérias/patogenicidade , Membrana Celular/metabolismo , Endocitose , HumanosRESUMO
Actin polymerization plays a critical role in clathrin-mediated endocytosis in many cell types, but how polymerization is regulated is not known. Hip1R may negatively regulate actin assembly during endocytosis because its depletion increases actin assembly at endocytic sites. Here, we show that the C-terminal proline-rich domain of Hip1R binds to the SH3 domain of cortactin, a protein that binds to dynamin, actin filaments and the Arp2/3 complex. We demonstrate that Hip1R deleted for the cortactin-binding site loses its ability to rescue fully the formation of abnormal actin structures at endocytic sites induced by Hip1R siRNA. To determine when this complex might function during endocytosis, we performed live cell imaging. The maximum in vivo recruitment of Hip1R, clathrin and cortactin to endocytic sites was coincident, and all three proteins disappeared together upon formation of a clathrin-coated vesicle. Finally, we showed that Hip1R inhibits actin assembly by forming a complex with cortactin that blocks actin filament barbed end elongation.