Abstract
Autophosphorylation of inositol-requiring enzyme 1alpha (IRE1alpha) is required for its activation, which elicits the cellular unfolded protein response (UPR) and is functionally connected with insulin biosynthesis in pancreatic beta cells. We found that the scaffold protein receptor for activated C-kinase 1 (RACK1) interacted with IRE1alpha in a glucose-stimulated or endoplasmic reticulum (ER) stress-responsive manner in pancreatic beta cells and primary islets. RACK1 mediated the glucose-inducible assembly of a complex containing IRE1alpha, RACK1, and protein phosphatase 2A (PP2A) to promote dephosphorylation of IRE1alpha by PP2A, thereby inhibiting glucose-stimulated IRE1alpha activation and attenuating IRE1alpha-dependent increases in insulin production. Moreover, IRE1alpha activation was increased and RACK1 abundance was decreased in a mouse model of diabetes. Thus, our findings demonstrate that RACK1 functions as a key component in regulating the IRE1alpha signaling pathway in pancreatic beta cells.
MeSH terms
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Animals
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Blotting, Western
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Cell Line
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Cell Line, Tumor
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Endoplasmic Reticulum / metabolism
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Endoribonucleases / genetics
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Endoribonucleases / metabolism*
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Female
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GTP-Binding Proteins / genetics
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GTP-Binding Proteins / metabolism*
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Glucose / pharmacology*
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HT29 Cells
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Humans
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Insulin / metabolism
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Insulin-Secreting Cells / drug effects*
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Insulin-Secreting Cells / metabolism
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Islets of Langerhans / metabolism
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Male
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Mice
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Mice, Inbred C57BL
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Multiprotein Complexes / metabolism
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Neoplasm Proteins / genetics
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Neoplasm Proteins / metabolism*
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Obesity, Morbid / metabolism
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Phosphorylation / drug effects
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Protein Binding
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Protein Phosphatase 2 / genetics
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Protein Phosphatase 2 / metabolism
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Protein Serine-Threonine Kinases / genetics
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Protein Serine-Threonine Kinases / metabolism*
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Receptors for Activated C Kinase
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Receptors, Cell Surface / genetics
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Receptors, Cell Surface / metabolism*
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Reverse Transcriptase Polymerase Chain Reaction
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Two-Hybrid System Techniques
Substances
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Insulin
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Multiprotein Complexes
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Neoplasm Proteins
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RACK1 protein, human
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Receptors for Activated C Kinase
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Receptors, Cell Surface
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ERN1 protein, human
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Protein Serine-Threonine Kinases
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Endoribonucleases
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Protein Phosphatase 2
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GTP-Binding Proteins
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Glucose