Noncanonical Activation of Akt/Protein Kinase B in β-Cells by the Incretin Hormone Glucose-dependent Insulinotropic Polypeptide
Therapeutics based on the actions of the incretin hormones, glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), have recently been introduced for the treatment of type 2 diabetes mellitus. The serine/threonine kinase Akt is a major mediator of incretin action on t...
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Published in | The Journal of biological chemistry Vol. 284; no. 16; p. 10764 |
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Main Authors | , , , |
Format | Journal Article |
Language | English |
Published |
American Society for Biochemistry and Molecular Biology
17.04.2009
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Online Access | Get full text |
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Summary: | Therapeutics based on the actions of the incretin hormones, glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic
polypeptide (GIP), have recently been introduced for the treatment of type 2 diabetes mellitus. The serine/threonine kinase
Akt is a major mediator of incretin action on the pancreatic islet, increasing β-cell mass and function and promoting β-cell
survival. The mechanisms underlying incretin activation of Akt are thought to involve an essential phosphoinositide 3-kinase-mediated
phosphorylation of threonine 308, similar to the prototypical Akt activator, insulin-like growth factor-I (IGF-I). In this
study, using activity assays on immunoprecipitated Akt, we discovered that GIP and GLP-1 were capable of stimulating Akt in
the INS-1 β-cell line and isolated mouse islets via a mechanism that did not require phosphoinositide 3-kinase or phosphorylation
of Thr 308 and Ser 473 , and this pathway involved the production of cAMP. Furthermore, we found that GIP stimulated anti-apoptotic signaling via
this alternate mode of Akt activation. We conclude that incretins can activate Akt via a novel noncanonical mechanism that
may provide an alternative therapeutic target for the treatment of type 2 diabetes mellitus and have broader implications
for Akt physiology in human health and disease. |
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ISSN: | 0021-9258 1083-351X |
DOI: | 10.1074/jbc.M809116200 |