The small GTPase Rab1b colocalizes with autophagic vacuoles

ZOPPINO FCM AND COLOMBO M.I.

Iguazu Misiones Argentina

Congreso; XL Reunión Anual de la Sociedad Argentina de Bioquímica y Biología Molecular (SAIB); 2004

SAIB

Our search is centered in finding  molecules that regulate the traffic in the autophagy pathway. Autophagy is a bulk protein degradation process, in which portions of citoplasm and/or organellas are sequestered by membranes to form vesicles called autophagosomes, which fussion with lysosomes for their degradation. Intracellular tubulovesicular  trafficking is regulated by members of the Rab GTPase family that belong to Ras superfamily of small molecular weight GTPases. Since principles of the 90’ is well known the function of Rab1 promoting the anterograde transport between ER and Golgi membranes.  We have followed, with the help of fluorescence or confocal microscopy, the behavior of GFP Rabs1b wt and mutants, during autophagy by means of the use of different autophagosome markers: GFP/RFP-LC3, Monodansylcada verine; under different conditions that stimulate autophagy such as starvation or  rapamicyn. Our data suggest that Rab1 localize in early autophagosomes marked with RFP-LC3, and it remains until the late stage of autophagolysosome, as it demonstrates the acquisition of Cathepsin D, a lysosomal marker. Moreover, Rab 1 requires to be in its active form to anchor in autophagic membranes , since its mutant S22N with impaired capacity to bound GTP, does not colocalize with MDC marked vesicles.