COBRE: LSU HSC: P4: ER TO GOLGI T & VSMC

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The objective of this project is to determine the role of altered ER-to-Golgi trafficking of angiotensin II type 1 receptor (AT1R) and beta 2 adrenergic receptor (AR) in primary cultures of neonatal rat ventricular myocytes and vascular smooth muscle cells. There are three specific aims. First aim is to define the role of Rab1 and other vesicular transport regulators (Sar1, ARF1, Rab2 and Rab6) in the endoplasmic reticulum-to-Golgi transport. Second aim is to determine if alterations in the ER-to-Golgi transport, as a consequence of manipulating Rab1 function, is involved in receptor signaling. Third Aim is to determine the effect of Rab1 on protein expression profile. In the second year, the studies have been carried out to define the molecular mechanisms underlying the intracellular trafficking from the ER through the Golgi to the cell surface of G protein-coupled receptors and their possible involvement in the development of cardiac myocyte hypertrophy. We have investigated: (1) the role of Rab1 in regulating the transport and signaling of AT1R, alpha1-AR and beta-AR and hypertrophic responses in neonatal mycoytes. We have demonstrated that adenovirus-mediated gene transfer of wild-type Rab1 differentially modified the cell-surface targeting and signaling of AT1R, alpha1-AR and beta-AR as well as receptor-mediated hypertrophic responses. (2) the role of dimerization in alpha2-AR trafficking and signaling. We demonstrated that alpha2B-AR mutant defective in ER export functions as a dominant negative mutant for the export and signaling of its wild-type counterpart as well as other alpha2-AR. These data provide new and important information regarding the regulation of GPCR export and function.