Connective tissue growth factor/CCN2 stimulates actin disassembly through Akt/protein kinase B‐mediated phosphorylation and cytoplasmic translocation of p27
            Kip‐1

In vivo, CCN2 (connective tissue growth factor) promotes angiogenesis, osteogenesis, tissue repair, and fibrosis, through largely unknown mechanisms. In vitro, CCN2 promotes cell adhesion in a variety of systems via integrins and heparin sulfate proteoglycans (HSPGs). However, the physiological relevance of CCN2-mediated cell adhesion is unknown. Here, we find that HSPGs and the mitogen-activated protein kinase kinase/extracellular signal-regulated kinase (ERK) mitogen-activated protein kinase cascade are required for adult human dermal fibroblasts to adhere to CCN2. Endogenous CCN2 directly binds fibronectin and the fibronectin receptors integrins α4 β1 and α5 and syndecan 4. Using Ccn2-/- mouse embryonic fibroblasts, we show that loss of endogenous CCN2 results in impaired spreading on fibronectin, delayed α-smooth muscle actin stress fiber formation, and reduced ERK and focal adhesion kinase phosphorylation. These results suggest that a physiological role of CCN2 is to potentiate the ability of fibroblasts to spread on fibronectin, which may be important in modulating fibroblast adhesion to the provisional matrix during tissue development and wound healing. These results are consistent with the notion that a principal function of CCN2 is to modulate receptor/ligand interactions in vivo.

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Effect of Connective Tissue Growth Factor on Protein Kinase Expression and Activity in Human Corneal Fibroblasts

Investigative Opthalmology & Visual Science ◽

10.1167/iovs.12-10790 ◽

2012 ◽

Vol 53 (13) ◽

pp. 8076 ◽

Cited By ~ 9

Author(s):

Siva S. Radhakrishnan ◽

Timothy D. Blalock ◽

Paulette M. Robinson ◽

Genevieve Secker ◽

Julie Daniels ◽

...

Keyword(s):

Growth Factor ◽

Protein Kinase ◽

Connective Tissue ◽

Connective Tissue Growth Factor ◽

Tissue Growth ◽

Corneal Fibroblasts ◽

Kinase Expression ◽

Expression And Activity

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Expression of Connective Tissue Growth Factor in Human Renal Fibroblasts: Regulatory Roles of RhoA and cAMP

Journal of the American Society of Nephrology ◽

10.1681/asn.v1291853 ◽

2001 ◽

Vol 12 (9) ◽

pp. 1853-1861 ◽

Cited By ~ 1

Author(s):

JULIANE HEUSINGER-RIBEIRO ◽

MICHAEL EBERLEIN ◽

NADIA ABDEL WAHAB ◽

MARGARETE GOPPELT-STRUEBE

Keyword(s):

Growth Factor ◽

Protein Kinase ◽

Connective Tissue ◽

Protein Kinase A ◽

Connective Tissue Growth Factor ◽

Tissue Growth ◽

Cytochalasin D ◽

Small Gtpase ◽

General Role ◽

Kinase A

Abstract. The induction of connective tissue growth factor (CTGF) was investigated in a human renal fibroblast cell line that exhibited many characteristics of primary human renal fibroblasts. Induction of CTGF mRNA was observed after treatment of the cells with transforming growth factor-β (TGF-β) or, even more prominently, lysophosphatidic acid (LPA). LPA induced a rapid transient increase in CTGF mRNA expression, with maximal levels being observed after 1 to 2 h. This increase was accompanied by CTGF protein synthesis. Induction of CTGF was insensitive to pertussis toxin and was not dependent on the activation of p42/44 mitogen-activated protein kinases. Inhibition of the proteins of the Rho family with toxin B from Clostridium difficile abrogated basal and LPA-mediated induction of CTGF. Specific targeting of RhoA with C3 exotoxin or of the Rho kinases with the inhibitor Y-27632 similarly prevented induction of CTGF, implicating RhoA as a signaling module downstream of LPA. Inhibition of RhoA depolymerized the actin cytoskeleton, as did treatment with cytochalasin D. Preincubation of the human renal fibroblasts with cytochalasin D prevented induction of CTGF by LPA, indicating a strong contribution of an intact cytoskeleton. Interference with RhoA signaling similarly inhibited the induction of CTGF by TGF-β. Elevation of intracellular levels of cAMP and thus activation of protein kinase A prevented induction of CTGF expression. The cytoskeletal effects of cAMP, however, were reversed by LPA. These data indicate complex interactions involving LPA-mediated activation of RhoA- and protein kinase A-dependent signaling pathways. The data thus demonstrate the regulatory functions of the small GTPase RhoA and of an intact cytoskeleton in the expression of CTGF after stimulation with LPA or TGF-β. Analogous signal transduction pathways were previously demonstrated in rat mesangial cells, suggesting a more general role for RhoA in the regulation of CTGF expression.

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