title: Insulin-induced beta-arrestin1 Ser-412 phosphorylation is a mechanism for desensitization of ERK activation by Galphai-coupled receptors.
abstract: Beta-arrestin1 is an adapter/scaffold for many G protein-coupled receptors during mitogen-activated protein kinase signaling. Phosphorylation of beta-arrestin1 at position Ser-412 is a regulator of beta-arrestin1 function, and in the present study, we showed that insulin led to a time- and dose-dependent increase in beta-arrestin1 Ser-412 phosphorylation, which blocked isoproterenol- and lysophosphatidic acid-induced Ser-412 dephosphorylation and impaired ERK signaling by these G protein-coupled receptor ligands. Insulin treatment also led to accumulation of Ser-412-phosphorylated beta-arrestin1 at the insulin-like growth factor 1 receptor and prevented insulin-like growth factor 1/Src association. Insulin-induced Ser-412 phosphorylation was partially dependent on ERK as treatment with the MEK inhibitor PD98059 inhibited the insulin effect (62% reduction, p = 0.03). Inhibition of phosphatidylinositol 3-kinase by wortmannin did not have a significant effect (9% reduction, p = 0.41). We also found that the protein phosphatase 2A (PP2A) was in a molecular complex with beta-arrestin1 and that the PP2A inhibitor okadaic acid increased Ser-412 phosphorylation. Concomitant addition of insulin and okadaic acid did not produce an additive effect on Ser-412 phosphorylation, suggesting a common mechanism. Small t antigen specifically inhibited PP2A, and in HIRcB cells expressing small t antigen, beta-arrestin1 Ser-412 phosphorylation was increased, and insulin had no further effect. Insulin treatment caused increased beta-arrestin1 Ser-412 phosphorylation, which blocked mitogen-activated protein kinase signaling and internalization by beta-arrestin1-dependent receptors with no effect on beta-adrenergic receptor Gs-mediated cAMP production. These findings provide a new mechanism for insulin-induced desensitization of ERK activation by Galphai-coupled receptors.
authors.affiliation: Department of Medicine, Division of Endocrinology and Metabolism, University of California, San Diego, La Jolla 92093, USA.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Hupfeld
authors.forename: Jamie L
authors.initials: JL
authors.lastname: Resnik
authors.forename: Satoshi
authors.initials: S
authors.lastname: Ugi
authors.forename: Jerrold M
authors.initials: JM
authors.lastname: Olefsky
mesh_terms: D000957:Antigens, Viral, Tumor / Q000378:metabolism; D019390:Arrestins / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D020962:Heterotrimeric GTP-Binding Proteins / Q000378:metabolism; D007328:Insulin / Q000494:pharmacology; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D020935:MAP Kinase Signaling System; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D019319:Okadaic Acid / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D010768:Phosphoserine / Q000378:metabolism; D011485:Protein Binding; D054648:Protein Phosphatase 2; D017526:Receptor, IGF Type 1 / Q000378:metabolism; D011943:Receptors, Adrenergic, beta / Q000378:metabolism; D013997:Time Factors; D000071557:beta-Arrestins
chemical_list: D000957:Antigens, Viral, Tumor; D019390:Arrestins; D007328:Insulin; D011943:Receptors, Adrenergic, beta; D000071557:beta-Arrestins; D010768:Phosphoserine; D019319:Okadaic Acid; D007334:Insulin-Like Growth Factor I; D019869:Phosphatidylinositol 3-Kinases; D017526:Receptor, IGF Type 1; D020928:Mitogen-Activated Protein Kinases; D010749:Phosphoprotein Phosphatases; D054648:Protein Phosphatase 2; D020962:Heterotrimeric GTP-Binding Proteins