title: PKCepsilon mediates glucose-regulated insulin production in pancreatic beta-cells.
abstract: Endocrine cells produce large amounts of one or more peptides. The post-translational control of selective production of a single protein is often unknown. We used 3 unrelated approaches to diminish PKCepsilon in rat islets to evaluate its role in preferential glucose-mediated insulin production. Transfection with siRNA (siR-PKCepsilon) or expression of inactive PKCepsilon (PKCepsilon-KD) resulted in a significant reduction in insulin response to glucose (16.7 mmol/l). Glucose stimulation resulted in concentration of PKCepsilon in the perinuclear region, an area known to be rich in ER-Golgi systems, associated with insulin-containing structures. ss'COP1 (RACK2) is the anchoring protein for PKCepsilon. Glucose-stimulated proinsulin production was diminished by 50% in islets expressing PKCepsilon-KD, and 60% in islets expressing RACK2 binding protein (epsilonV1-2); total protein biosynthesis was not affected. In islets expressing epsilonV1-2, a chase period following glucose stimulus resulted in a reduced proinsulin conversion to mature insulin. We propose that PKCepsilon plays a specific role in mediating the glucose-signal into insulin production: binding to ss'COP1 localizes the activated enzyme to the RER where it modulates the shuttling of proinsulin to the TGN. Subsequently the enzyme may be involved in anterograde trafficking of the prohormone or in its processing within the TGN.
authors.affiliation: Endocrinology and Metabolism Service, Department of Medicine, The Hebrew University - Hadassah Medical Center, Jerusalem, Israel.
authors.forename: Nasim
authors.initials: N
authors.lastname: Warwar
authors.forename: Avital
authors.initials: A
authors.lastname: Dov
authors.forename: Eva
authors.initials: E
authors.lastname: Abramovitch
authors.forename: Ren
authors.initials: R
authors.lastname: Wu
authors.forename: Marina
authors.initials: M
authors.lastname: Jmoudiak
authors.forename: Esther
authors.initials: E
authors.lastname: Haber
authors.forename: Erol
authors.initials: E
authors.lastname: Cerasi
authors.forename: Rafael
authors.initials: R
authors.lastname: Nesher
mesh_terms: D000818:Animals; D001483:Base Sequence; D002478:Cells, Cultured; D004789:Enzyme Activation; D015971:Gene Expression Regulation, Enzymologic; D005947:Glucose / Q000494:pharmacology*; D007328:Insulin / Q000096:biosynthesis* / Q000378:metabolism; D000078790:Insulin Secretion; D050417:Insulin-Secreting Cells / Q000187:drug effects* / Q000378:metabolism*; D008297:Male; D051744:Protein Kinase C-epsilon / Q000235:genetics / Q000378:metabolism*; D021381:Protein Transport; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction
chemical_list: D007328:Insulin; D051744:Protein Kinase C-epsilon; D005947:Glucose