Rga6 is a Rho GAP involved in fission yeast polarized growth

Resumen del póster presentado al American Society for Cell Biology (ASCB) Annual Meeting: "Cell Biology", celebrado en San Diego, California (US) del 12 al 16 de diciembre de 2015.Fission yeast Cdc42 is essential for polarized growth and the maintenance of cell dimensions and cylindrical morphology. This GTPase is positively regulated by the GEFs Scd1 and Gef1 and negatively regulated by the GAP Rga4. This study establishes that the protein Rga6 is also a Cdc42 GAP that collaborates with Rga4 in the maintenance of fission yeast shape and the restriction of growth to the tip area. Cells lacking Rga6 are viable but slightly shorter and broader than wild type, and cells lacking simultaneously both GAPs are rounded. In these cells, active Cdc42 is observed all along the membrane. Overexpression of rga6+ for brief periods of time (12-20h) causes cells to elongate, and grow in a monopolar way, as does overexpression of Rga4, and for longer times is deleterious. Rga6 localizes to the plasma membrane forming clusters which are different from those formed by Rga4. Rga6 clusters are very dynamic and move by lateral diffusion. A polybasic region at the Rga6 C-terminus is responsable for its membrane localization. Rga6-GFP fluorescence is considerably reduced at the growing tips and this reduction is dependent on the N-terminal region of Rga6 and on the actin cables made by the formin For3. We propose here that Rga6 participates in the regulation of active Cdc42 localization and in the amplitude of active Cdc42 oscillations at the cell tips.Peer Reviewe