Connective tissue growth factor [CTGF]/CCN2 stimulates mesangial cell migration through integrated dissolution of focal adhesion complexes and activation of cell polarization.
Connective tissue growth factor [CTGF]/CCN2 is a prototypic member of the CCN family of regulatory proteins. CTGF expression is up-regulated in a number of fibrotic diseases, including diabetic nephropathy, where it is believed to act as a downstream mediator of TGF-beta function; however, the exact mechanisms whereby CTGF mediates its effects remain unclear. Here, we describe the role of CTGF in cell migration and actin disassembly in human mesangial cells, a primary target in the development of renal glomerulosclerosis. The addition of CTGF to primary mesangial cells induced cell migration and cytoskeletal rearrangement but had no effect on cell proliferation. Cytoskeletal rearrangement was associated with a loss of focal adhesions, involving tyrosine dephosphorylation of focal adhesion kinase and paxillin, increased activity of the protein tyrosine phosphatase SHP-2, with a concomitant decrease in RhoA and Rac1 activity. Conversely, Cdc42 activity was increased by CTGF. These functional responses were associated with the phosphorylation and translocation of protein kinase C-zeta to the leading edge of migrating cells. Inhibition of CTGF-induced protein kinase C-zeta activity with a myristolated PKC-zeta inhibitor prevented cell migration. Moreover, transient transfection of human mesangial cells with a PKC-zeta kinase inactive mutant (dominant negative) expression vector also led to a decrease in CTGF-induced migration compared with wild-type. Furthermore, CTGF stimulated phosphorylation and activation of GSK-3beta. These data highlight for the first time an integrated mechanism whereby CTGF regulates cell migration through facilitative actin cytoskeleton disassembly, which is mediated by dephosphorylation of focal adhesion kinase and paxillin, loss of RhoA activity, activation of Cdc42, and phosphorylation of PKC-zeta and GSK-3beta. These changes indicate that the initial stages of CTGF mediated mesangial cell migration are similar to those involved in the process of cell polarization. These findings begin to shed mechanistic light on the renal diabetic milieu, where increased CTGF expression in the glomerulus contributes to cellular dysfunction.
Department of Medicine and Therapeutics, Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield, Dublin 4, Ireland. john.crean@ucd.ie
J K
JK
Crean
F
F
Furlong
D
D
Finlay
D
D
Mitchell
M
M
Murphy
B
B
Conway
H R
HR
Brady
C
C
Godson
F
F
Martin
D000199:Actins / Q000737:chemistry / Q000378:metabolism; D002465:Cell Movement / Q000187:drug effects*; D016764:Cell Polarity / Q000187:drug effects*; D002478:Cells, Cultured; D055513:Connective Tissue Growth Factor; D003598:Cytoskeletal Proteins / Q000378:metabolism; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D022001:Focal Adhesions / Q000187:drug effects*; D005920:Glomerular Mesangium / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; 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*; D047908:Intracellular Signaling Peptides and Proteins; D051419:Paxillin; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011493:Protein Kinase C / Q000378:metabolism; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D020742:rhoA GTP-Binding Protein / Q000378:metabolism; D000099221:Protein Kinase C zeta
D000199:Actins; D055513:Connective Tissue Growth Factor; D003598:Cytoskeletal Proteins; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D038362:Glycogen Synthase Kinase 3; D000071679:Glycogen Synthase Kinase 3 beta; D017874:Immediate-Early Proteins; D036341:Intercellular Signaling Peptides and Proteins; D047908:Intracellular Signaling Peptides and Proteins; D051419:Paxillin; D010750:Phosphoproteins; D011493:Protein Kinase C; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D017027:Protein Tyrosine Phosphatases; D011505:Protein-Tyrosine Kinases; D020742:rhoA GTP-Binding Protein; D000099221:Protein Kinase C zeta; C526317:CCN2 protein, human; C496061:PXN protein, human; C496050:PTK2 protein, human; C000605506:GSK3B protein, human; C516724:PTPN11 protein, human