A novel signal for endocytosis and polarity in yeast

GONZALO BIGLIANI; AYELEN GONZALEZ MONTORO; JAVIER VALDEZ TAUBAS

Córdoba

Congreso; LII Reunión Anual de SAIB; 2016

SAIB

A novel signal for endocytosis and polarity in yeast Gonzalo Bigliani, Ayelén Gonzalez Montoro, , and Javier Valdez Taubas. CIQUIBIC, CONICET - Depto de Química Biológica, Fac. Ciencias Quimicas, Univ. Nac. de Córdoba. 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 is homogenously 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, and were not able to identify a specific adaptor for this signal. We did observe a dependence on the ubiquitin ligase Rsp5. Interestingly, a mutant Sso1 chimera devoid of lysines is still polarized, suggesting that a ubiqutinated adaptor for this novel signal must exist.