A transmembrane domain with a high-volume exoplasmic half is a novel signal for membrane protein endocytosis and polarity in Saccharomyces cerevisiae

AYELEN GONZALEZ MONTORO; GONZALO BIGLIANI; JAVIER VALDEZ TAUBAS

Puerto Natales

Workshop; EMBO Workshop: Current advances in membrane trafficking ? Implications for polarity and Disease; 2014

European Molecualr Biology Organization

A transmembrane domain with a high-volume exoplasmic half is a novel signal for membrane protein endocytosis and polarity in Saccharomyces cerevisiae. Ayelén González Montoro, Gonzalo Bigliani, Javier Valdez Taubas Centro de Investigaciones en Química Biológica de Córdoba, CIQUIBIC (UNC-CONICET), Departamento de Química Biológica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba Endocytosis is a crucial process for cells, allowing them to incorporate material from the extracellular space and to control the availability of receptors, transporters and other transmembrane proteins in the plasma membrane. In Saccharomyces cerevisiae, endocytosis followed by recycling to the plasma membrane results in a polarized distribution of membrane proteins by a kinetic mechanism. The classical model for endocytosis of transmembrane proteins involves cytosolic signals that interact with adaptor proteins, driving active concentration of cargo in endocytic vesicles. As part of a systematic analysis of the influence of the transmembrane domain (TMD) length and volume in intracellular localization of type-two membrane proteins, we observed that increasing the volume of the residues that constitute the exoplasmic hemi-TMD of the yeast SNARE Sso1, which is homogenously distributed in the plasma membrane, resulted in a polarized distribution of the mutant protein both in cells and shmoos. Expression of this mutant protein in strains affected in either endocytosis or recycling revealed that this polarization is achieved by endocytic cycling. A bioinformatic search of the Saccharomyces cerevisiae proteome identified several proteins with high-volume exoplasmic hemi-TMDs, some of which have been reported to exhibit a polarized distribution. Our experiments show that the TMDs of these proteins are able to confer a polarized distribution to the cytoplasmic domain of Sso1, indicating that the geometry of the TMD can act as an endocytic and polarity determinant in vivo. We are currently trying to determine the mechanism by which this type of TMD mediates incorporation into clathrin coated vesicles, both by in vivo and in vitro experiments