The secretory pathway and its adaptation to a high secretory demand

MARTINEZ, H; SAMPIERI, L; GARCIA IA; ALVAREZ, C

Rosario, Santa Fe

Simposio; SAIB 2014; 2014

SAIB

Membrane transport from the ER to the Golgi complex requires multiple molecules located in at least three distinct membrane entities: at specialized subdomains of the Endoplasmic reticulum called ERES (ER exit sites), at VTCs (Vesicular tubular clusters) and at cis-Golgi network. The mammalian Rab1 GTPase is essential for ER to Golgi transport and, through its interactions with diverse effector proteins, regulates the formation, tethering and fusion of transport carriers derived from the ER. It is clear that Rab1b is acting in sequential stages at the ER-Golgi transport and we propose a model that postulates that Rab1b is a coordinator of this step of transport.Furthermore, since Rab1 isoforms (Rab1a and Rab1b) are ubiquitous and different tissues express dissimilar mRNA levels of Rab1 isoforms, we also analyzed cellular effects induced by changes of Rab1b levels. We report that an increase in Rab1b levels induces changes in Golgi structure and gene expression. Such gene expression changes require the activation of p38 mitogen-activated protein kinase (MAPK) and the cAMP-responsive element-bindingprotein (CREB) binding consensus site. The data strongly suggest that a Rab1b increase is required to elicit a secretory response.