beta-Arrestin-mediated ADP-ribosylation factor 6 activation and beta 2-adrenergic receptor endocytosis.
beta-Arrestins are multifunctional adaptor proteins known to regulate internalization of agonist-stimulated G protein-coupled receptors by linking them to endocytic proteins such as clathrin and AP-2. Here we describe a previously unappreciated mechanism by which beta-arrestin orchestrates the process of receptor endocytosis through the activation of ADP-ribosylation factor 6 (ARF6), a small GTP-binding protein. Involvement of ARF6 in the endocytic process is demonstrated by the ability of GTP-binding defective and GTP hydrolysis-deficient mutants to inhibit internalization of the beta(2)-adrenergic receptor. The importance of regulation of ARF6 function is shown by the ability of the ARF GTPase-activating protein GIT1 to inhibit and of the ARF nucleotide exchange factor, ARNO, to enhance receptor endocytosis. Endogenous beta-arrestin is found in complex with ARNO. Upon agonist stimulation of the receptor, beta-arrestin also interacts with the GDP-liganded form of ARF6, thereby facilitating ARNO-promoted GTP loading and activation of the G protein. Thus, the agonist-driven formation of a complex including beta-arrestin, ARNO, and ARF6 provides a molecular mechanism that explains how the agonist-stimulated receptor recruits a small G protein necessary for the endocytic process and controls its activation.
Claing
A
A
Howard Hughes Medical Institute and Department of Medicine, Duke University Medical Center, Durham, North Carolina 27710, USA.
Chen
W
W
Miller
W E
WE
Vitale
N
N
Moss
J
J
Premont
R T
RT
Lefkowitz
R J
RJ
D000089982:ADP-Ribosylation Factor 6; D020727:ADP-Ribosylation Factors / Q000502:physiology*; D000818:Animals; D019390:Arrestins / Q000502:physiology*; D002478:Cells, Cultured; D004705:Endocytosis; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D018343:Receptors, Adrenergic, beta-2 / Q000378:metabolism*; D000071557:beta-Arrestins
D000089982:ADP-Ribosylation Factor 6; D019390:Arrestins; D018343:Receptors, Adrenergic, beta-2; D000071557:beta-Arrestins; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006160:Guanosine Triphosphate; D020727:ADP-Ribosylation Factors