title: Dysregulated intracellular signaling impairs CTGF-stimulated responses in human mesangial cells exposed to high extracellular glucose.
abstract: High ambient glucose activates intracellular signaling pathways to induce the expression of extracellular matrix and cytokines such as connective tissue growth factor (CTGF). Cell responses to CTGF in already glucose-stressed cells may act to transform the mesangial cell phenotype leading to the development of glomerulosclerosis. We analyzed cell signaling downstream of CTGF in high glucose-stressed mesangial cells to model signaling in the diabetic milieu. The addition of CTGF to primary human mesangial cells activates cell migration which is associated with a PKC-zeta-GSK3beta signaling axis. In high ambient glucose basal PKC-zeta and GSK3beta phosphorylation levels are selectively increased and CTGF-stimulated PKC-zeta and GSK3beta phosphorylation was impaired. These effects were not induced by osmotic changes. CTGF-driven profibrotic cell signaling as determined by p42/44 MAPK and Akt phosphorylation was unaffected by high glucose. Nonresponsiveness of the PKC-zeta-GSK3beta signaling axis suppressed effective remodeling of the microtubule network necessary to support cell migration. However, interestingly the cells remain plastic: modulation of glucose-induced PKC-beta activity in human mesangial cells reversed some of the pathological effects of glucose damage in these cells. We show that inhibition of PKC-beta with LY379196 and PKC-beta siRNA reduced basal PKC-zeta and GSK3beta phosphorylation in human mesangial cells exposed to high glucose. CTGF stimulation under these conditions again resulted in PKC-zeta phosphorylation and human mesangial cell migration. Regulation of PKC-zeta by PKC-beta in this instance may establish PKC-zeta as a target for constraining the progression of mesangial cell dysfunction in the pathogenesis of diabetic nephropathy.
authors.affiliation: UCD School of Biomolecular and Biomedical Science, Conway Institute, University College Dublin, Belfield, Dublin, Ireland.
authors.forename: Fiona
authors.initials: F
authors.lastname: Furlong
authors.forename: John
authors.initials: J
authors.lastname: Crean
authors.forename: Laura
authors.initials: L
authors.lastname: Thornton
authors.forename: Ronan
authors.initials: R
authors.lastname: O'Leary
authors.forename: Madeline
authors.initials: M
authors.lastname: Murphy
authors.forename: Finian
authors.initials: F
authors.lastname: Martin
mesh_terms: D015153:Blotting, Western; D002478:Cells, Cultured; D002633:Chemotaxis / Q000187:drug effects; D055513:Connective Tissue Growth Factor; D003928:Diabetic Nephropathies / Q000473:pathology; D004591:Electrophoresis, Polyacrylamide Gel; D005110:Extracellular Space / Q000187:drug effects / Q000378:metabolism; D005920:Glomerular Mesangium / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D005947:Glucose / Q000633:toxicity*; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D006801:Humans; D017874:Immediate-Early Proteins / Q000494:pharmacology*; D036341:Intercellular Signaling Peptides and Proteins / Q000494:pharmacology*; D008856:Microscopy, Fluorescence; D051744:Protein Kinase C-epsilon / Q000378:metabolism; D034741:RNA, Small Interfering / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects*; D013268:Stimulation, Chemical; D014947:Wounds and Injuries / Q000473:pathology; D020764:cdc42 GTP-Binding Protein / Q000096:biosynthesis
chemical_list: C526317:CCN2 protein, human; D017874:Immediate-Early Proteins; D036341:Intercellular Signaling Peptides and Proteins; D034741:RNA, Small Interfering; D055513:Connective Tissue Growth Factor; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; D051744:Protein Kinase C-epsilon; D038362:Glycogen Synthase Kinase 3; D020764:cdc42 GTP-Binding Protein; D005947:Glucose