A novel signal for endocytosis and polarity in yeast

BIGLIANI GONZALO YAMIL; GONZÁLEZ MONTORO AYELÉN; VALDEZ TAUBAS JAVIER

Córdoba

Congreso; - SAIB - 52 th Annual Meeting Argentine Society for Biochemistry and Molecular Biology; 2016

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

In Saccharomyces cerevisiae, polarized distribution of plasma membrane proteins is maintained kinetically due to polarized secretion followed by endocytic recycling. The classical model for endocytosis of transmembrane proteins involves the recognition of cytosolic signals by adaptor proteins that drive the active concentration of cargoes in endocytic vesicles. We previously observed that increasing the volume of residues that constitute the exoplasmic hemi-TransMembrane Domain (TMD) of the yeast SNARE Sso1, which ishomogenously distributed in the plasma membrane, results in its polarized localization and this is dependent in endocytosis and recycling. Naturally occurring high-volume exoplasmic hemi-TMDs are also able to confer a polarized distribution to the cytoplasmic domain of Sso1, confirming that the geometry of TMDs represent a novel determinant for endocytosis and polarity. To gain insight into the mechanism involved in the endocytosis of this novel signal, we tested numerous yeast mutants that allowed us to confirm that internalization is clathrin mediated. We tested all known endocytosis adaptors but we were able to identify a specific adaptor for these TMDs. We observed a dependence on the ubiquitin ligase Rsp5. Interestingly, a mutant Sso1 chimera devoid of lysines is stillpolarized, suggesting that a ubiqutinated adaptor for this novel signal must exist.