beta-Arrestin 1 and 2 differentially regulate heptahelical receptor signaling and trafficking.
The two widely coexpressed isoforms of beta-arrestin (termed beta arrestin 1 and 2) are highly similar in amino acid sequence. The beta-arrestins bind phosphorylated heptahelical receptors to desensitize and target them to clathrin-coated pits for endocytosis. To better define differences in the roles of beta-arrestin 1 and 2, we prepared mouse embryonic fibroblasts from knockout mice that lack one of the beta-arrestins (beta arr1-KO and beta arr2-KO) or both (beta arr1/2-KO), as well as their wild-type (WT) littermate controls. These cells were analyzed for their ability to support desensitization and sequestration of the beta(2)-adrenergic receptor (beta(2)-AR) and the angiotensin II type 1A receptor (AT(1A)-R). Both beta arr1-KO and beta arr2-KO cells showed similar impairment in agonist-stimulated beta(2)-AR and AT(1A)-R desensitization, when compared with their WT control cells, and the beta arr1/2-KO cells were even further impaired. Sequestration of the beta(2)-AR in the beta arr2-KO cells was compromised significantly (87% reduction), whereas in the beta arr1-KO cells it was not. Agonist-stimulated internalization of the AT(1A)-R was only slightly reduced in the beta arr1-KO but was unaffected in the beta arr2-KO cells. In the beta arr1/2-KO cells, the sequestration of both receptors was dramatically reduced. Comparison of the ability of the two beta-arrestins to sequester the beta(2)-AR revealed beta-arrestin 2 to be 100-fold more potent than beta-arrestin 1. Down-regulation of the beta(2)-AR was also prevented in the beta arr1/2-KO cells, whereas no change was observed in the single knockout cells. These findings suggest that sequestration of various heptahelical receptors is regulated differently by the two beta-arrestins, whereas both isoforms are capable of supporting receptor desensitization and down-regulation.
Kohout
T A
TA
Howard Hughes Medical Institute, Department of Medicine, Duke University Medical Center, Durham, NC 27710, USA.
Lin
F S
FS
Perry
S J
SJ
Conner
D A
DA
Lefkowitz
R J
RJ
D000818:Animals; D019390:Arrestins / Q000378:metabolism* / Q000502:physiology; D002460:Cell Line; D000242:Cyclic AMP / Q000378:metabolism; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D010716:Phosphatidylinositols / Q000378:metabolism; D020033:Protein Isoforms / Q000378:metabolism / Q000502:physiology; D044140:Receptor, Angiotensin, Type 1; D018343:Receptors, Adrenergic, beta-2 / Q000235:genetics / Q000378:metabolism*; D011945:Receptors, Angiotensin / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D000071559:beta-Arrestin 1; D000071560:beta-Arrestin 2; D000071557:beta-Arrestins
C000605253:ARRB1 protein, human; C000605254:ARRB2 protein, human; C000605255:Arrb1 protein, mouse; C000605258:Arrb2 protein, mouse; D019390:Arrestins; D010716:Phosphatidylinositols; D020033:Protein Isoforms; D044140:Receptor, Angiotensin, Type 1; D018343:Receptors, Adrenergic, beta-2; D011945:Receptors, Angiotensin; D000071559:beta-Arrestin 1; D000071560:beta-Arrestin 2; D000071557:beta-Arrestins; D000242:Cyclic AMP