Enhancement of the recycling and activation of beta-adrenergic receptor by Rab4 GTPase in cardiac myocytes.
We investigate the role of Rab4, a Ras-like small GTPase coordinating protein transport from the endosome to the plasma membrane, on the recycling and activation of endogenous beta-adrenergic receptor (beta-AR) in HL-1 cardiac myocytes in vitro and transgenic mouse hearts in vivo. Beta1-AR, the predominant subtype of beta-AR in HL-1 cardiac myocytes, was internalized after stimulation with isoproterenol (ISO) and fully recycled at 4 h upon ISO removal. Transient expression of Rab4 markedly facilitated recycling of internalized beta-AR to the cell surface and enhanced beta-AR signaling as measured by ISO-stimulated cAMP production. Transgenic overexpression of Rab4 in the mouse myocardium significantly increased the number of beta-AR in the plasma membrane and augmented cAMP production at the basal level and in response to ISO stimulation. Rab4 overexpression induced concentric cardiac hypertrophy with a moderate increase in ventricle/body weight ratio and posterior wall thickness and a selective up-regulation of the beta-myosin heavy chain gene. These data provide the first evidence indicating that Rab4 is a rate-limiting factor for the recycling of endogenous beta-AR and augmentation of Rab4-mediated traffic enhances beta-AR function in cardiac myocytes.
Department of Pharmacology and Experimental Therapeutics, Louisiana State University Health Sciences Center, New Orleans, Louisiana 70112, USA.
Catalin M
CM
Filipeanu
Fuguo
F
Zhou
May L
ML
Lam
Kenneth E
KE
Kerut
William C
WC
Claycomb
Guangyu
G
Wu
D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004452:Echocardiography; D004591:Electrophoresis, Polyacrylamide Gel; D015151:Immunoblotting; D007545:Isoproterenol / Q000494:pharmacology; D008024:Ligands; D051379:Mice; D008822:Mice, Transgenic; D009206:Myocardium / Q000378:metabolism; D032383:Myocytes, Cardiac / Q000201:enzymology* / Q000378:metabolism; D010641:Phenotype; D011943:Receptors, Adrenergic, beta / Q000378:metabolism*; D013997:Time Factors; D014162:Transfection; D019076:Transgenes; D015854:Up-Regulation; D024723:Ventricular Myosins / Q000737:chemistry; D020695:rab4 GTP-Binding Proteins / Q000378:metabolism*
D018076:DNA, Complementary; D008024:Ligands; D011943:Receptors, Adrenergic, beta; D000242:Cyclic AMP; D024723:Ventricular Myosins; D020695:rab4 GTP-Binding Proteins; D007545:Isoproterenol