ANALYSIS OF RAB1B CHANGES IN A SECRETORY CELL LINE

GARCIA IA, MONETTA P, SLAVIN I, ROMERO N, ALVAREZ C

Carlos Paz, Córdoba. Argentina

Congreso; XLIV Reunión Anual Sociedad Argentina de Bioquimica y Biologia Molecular (SAIB); 2008

SAIB

The isoforms of the GTPase Rab1 (Rab1a and b) are ubiquitous and essential for ER to Golgi transport but different tissues express dissimilar mRNA levels of Rab1a and Rab1b. Interestingly, levels of Rab1b mRNA are increased in secretory tissues such as the thyroid, prostate and epithelial lung cells. Our previous results shown that changes in Rab1b levels acted as a molecular switch to control the expression of a variety of genes by regulating both their promoter activity and protein levels. We postulate that activation of secretion could induce an increase in Rab1b levels that trigger signaling circuits essential for the synthesis of molecules necessary to coordinate the flux of membranes between trafficking organelles. To test this hypothesis, we used a thyroid secretory cell line to analyze protein changes after the addition of thyroid-stimulating hormone (TSH). We show that levels of some proteins involved in membrane transport, such us Rab1b, GM130, Pra1 and KDELR were increased upon the addition of TSH. Significantly, expression of the dominant negative Rab1b mutant inhibited the TSH-induced increase of GM130 and Pra1 suggesting that TSH treatment induce a global increase of Golgi proteins in a Rab1b-dependent mechanism. Our results indicate that Rab1b changes could play a role in the cellular response required for the adaptation to a physiological secretory stimulus.