Modulation of the Expression of Connective Tissue Growth Factor by Alterations of the Cytoskeleton

Abstract

Modulation of the cytoskeletal architecture was shown to regulate the expression of CTGF (connective tissue growth factor, CCN2). The microtubule disrupting agents nocodazole and colchicine strongly up-regulated CTGF expression, which was prevented upon stabilization of the microtubules by paclitaxel. As a consequence of microtubule disruption, RhoA was activated and the actin stress fibers were stabilized. Both effects were related to CTGF induction. Overexpression of constitutively active RhoA induced CTGF synthesis. Interference with RhoA signaling by simvastatin, toxinB, C3 toxin, and Y27632 prevented up-regulation of CTGF. Likewise, direct disintegration of the actin cytoskeleton by latrunculin B interfered with nocodazolemediated up-regulation of CTGF expression. Disassembly of actin fibers by cytochalasin D, however, unexpectedly increased CTGF expression indicating that the content of F-actin per se was not the major determinant for CTGF gene expression. Given the fact that cytochalasin D sequesters G-actin, a decrease in G-actin increased CTGF, while increased levels of Gactin corresponded to reduced CTGF expression. These data link alterations in the microtubule and actin cytoskeleton to the expression of CTGF and provide a molecular basis for the observation that CTGF is up-regulated in cells exposed to mechanical stress.

Up-Regulation of Connective Tissue Growth Factor in Endothelial Cells by the Microtubule-Destabilizing Agent Combretastatin A-4

“…Furthermore, microtubule disruption by CA-4P was linked to RhoA-Rho kinase signaling. Rho kinase activation leads to alterations of the actin cytoskeleton, which we have shown earlier to induce CTGF expression (23,25). Here, inhibition of the Rho kinase by the inhibitor Y27632 strongly reduced CA-4P-induced CTGF expression (Fig.…”

“…Upregulation of CTGF, which we observed in endothelial cells within hours after treatment with CA-4P, represents a novel aspect of CA-4P action, that is, the rapid induction of proteins with antiangiogenic properties. Up-regulation of CTGF by the microtubule-disrupting agents nocodazole or colchicine has been reported before (25); however, only the induction by CA-4P proved to be restricted to cells that formed a loose network and were not embedded in a dense cell monolayer. Furthermore, CTGF was up-regulated by CA-4P in cells forming tube-like structures on basement membrane gels.…”

“…In an earlier study in fibroblasts, we showed RhoAdependent CTGF induction when the microtubules were disrupted by colchicine or nocodazole (25,26). Therefore, we hypothesized that CA-4P by depolymerizing microtubules might regulate CTGF synthesis in endothelial cells.…”

Bone Morphogenetic Protein-7 and Connective Tissue Growth Factor: Novel Targets for Treatment of Renal Fibrosis?

“…In addition, in vitro studies with renal cells demonstrated that CTGF is also a direct target of gene regulation by TGF-β1-independent factors including high glucose, angiotensin II, aldosterone, hypoxia inducible factor-1α, and cyclic mechanical strain (124,125,(138)(139)(140)(141). The 3′-untranslated region of CTGF gene also contains regulatory sequences, of which the activity depends on as yet largely unidentified factors (142,143).…”

All in the CCN family: essential matricellular signaling modulators emerge from the bunker

“…Similarly, faithful expression of a reporter gene in transgenic mice, including in development and in response to wound healing, can be achieved if a 2 kb fragment of the CCN1 promoter is used, which indicates that this gene is also regulated at the level of transcription (Latinkic et al, 2001). Synthesis of CCN2 protein and mRNA is stimulated by specific growth factors, such as endothelin 1 and TGF␤, in addition to environment changes such as hypoxia and biomechanical stimuli (Grotendorst et al, 1996;Holmes et al, 2001;Ott et al, 2003;Shi-wen et al, 2004;Higgins et al, 2004) (Fig. 2).…”