Differential Regulation of the Cell-Surface Targeting and Function of β- and α₁-Adrenergic Receptors by Rab1 GTPase in Cardiac Myocytes

Abstract

The molecular mechanism underlying the export from the endoplasmic reticulum (ER) to the cell surface and its role in the regulation of signaling of adrenergic receptors (ARs) remain largely unknown. In this report, we determined the role of Rab1, a Ras-like GTPase that coordinates protein transport specifically from the ER to the Golgi, in the cell surface targeting and function of endogenous ␤-and ␣ 1 -ARs in neonatal rat ventricular myocytes. Adenovirus-driven expression of Rab1 into myocytes selectively increased the cell-surface number of ␣ 1 -AR, but not ␤-AR, whereas the dominant-negative mutant Rab1N124I significantly reduced the cell-surface expression of ␤-AR and ␣ 1 -AR. Brefeldin A inhibited ␤-AR and ␣ 1 -AR export and antagonized the Rab1 effect on ␣ 1 -AR expression. Manipulation of Rab1 function similarly influenced the transport of ␣ 1A -and ␣ 1B -ARs as well as ␤ 1 -and ␤ 2 -ARs. Fluorescent microscopy analysis demonstrated that expression of Rab1N124I and Rab1 small interfering RNA induced a marked accumulation of GFP-tagged ␤ 2 -AR and ␣ 1B -AR in the ER. Consistent with the effects on receptor cell-surface targeting, Rab1 selectively enhanced ERK1/2 activation and hypertrophic growth in response to the ␣ 1 -AR agonist phenylephrine but not to the ␤-AR agonist isoproterenol. Rab1N124I inhibited both agonist-mediated ERK1/2 activation and hypertrophic growth in neonatal myocytes. These results demonstrate that the cellsurface targeting and signaling of ␤-and ␣ 1 -ARs require Rab1 and are differentially modulated by augmentation of Rab1 function. Our data provide strong evidence implicating the ER-toGolgi traffic as a site for selective manipulation of distinct AR function in cardiac myocytes.

Targeting of the 5-HT1ASerotonin Receptor to Neuronal Dendrites Is Mediated by Yif1B

“…In this context, another IC protein, Rab1, has also been implicated in the intracellular trafficking of some GPCRs to the plasma membrane. Experiments inhibiting rab1 expression led to the characterization of rab1-dependent and -independent pathways from the ER to the plasma membrane depending on the GPCR studied (Wu et al, 2003;Filipeanu et al, 2006). Similarly, concerning another family of receptors, the regulation of a nicotinic acetylcholine receptor subtype trafficking has been recently described in Caenorhabditis elegans, revealing that its traffic depended on UNC-50, an endoplasmic reticulum-Golgi intermediate compartment (ERGIC)-associated protein (Eimer et al, 2007).…”

G Protein-Coupled Receptor Trafficking in Health and Disease: Lessons Learned to Prepare for Therapeutic Mutant Rescue in Vivo

“…Moreover, several studies have shown that manipulation of components involved in the ER export machinery may also selectively influence receptor PME and function. This is the case of the small GTPase Rab1 protein, a member of the Rab GTPase family of proteins (Martinez and Goud 1998); Rab1 is specifically localized in the ER and Golgi apparatus and regulates anterograde transport from the ER to and through the Golgi of several proteins (Yoo et al, 2002;Wu et al, 2003;Filipeanu et al, 2004Filipeanu et al, , 2006. Attenuation of Rab1 function by expressing DN Rab1 mutants or siRNA-mediated depletion of endogenous Rab1 inhibited cell surface expression of a number of endogenous GPCRs (including the angiotensin-1 receptor and the ␤ 2 -adrenergic receptor) and promoted their accumulation in the ER and the Golgi (Wu et al, 2003;Filipeanu et al, 2004).…”

ADP-Ribosylation Factors Modulate the Cell Surface Transport of G Protein-Coupled Receptors

“…As an initial approach to elucidate the mechanism of nascent GPCR targeting to the cell surface, we have determined the role of Sar1 and several Rab GTPases in regulating cell surface transport of representative GPCRs, including the angiotensin II and adrenergic receptor (AR) subfamilies (Wu et al, 2003;Filipeanu et al, 2004;Filipeanu et al, 2006;Dong et al, 2008;Zhang et al, 2009). Our studies indicate that the cell surface transport of different GPCRs may be mediated through distinct pathways and suggest a novel pathway mediating ␣ 2B -AR traffic from the ER to the Golgi apparatus (Wu et al, 2003).…”