Upregulation of the actin cytoskeleton via myocardin leads to increased expression of type 1 collagen
| Autor: | Zengdun Shi, Don C. Rockey |
|---|---|
| Rok vydání: | 2016 |
| Předmět: |
0301 basic medicine
Male Serum Response Factor RHOA macromolecular substances Collagen Type I Article Pathology and Forensic Medicine Extracellular matrix Rats Sprague-Dawley 03 medical and health sciences 0302 clinical medicine Hepatic Stellate Cells Animals Protein Isoforms Cytoskeleton Myofibroblasts Molecular Biology biology Chemistry Nuclear Proteins Cell Biology Actin cytoskeleton Actins 3. Good health Cell biology Rats Up-Regulation Actin Cytoskeleton 030104 developmental biology Myocardin 030220 oncology & carcinogenesis Hepatic stellate cell biology.protein Trans-Activators Myofibroblast Type I collagen |
| Zdroj: | Laboratory investigation; a journal of technical methods and pathology |
| ISSN: | 1530-0307 |
| Popis: | Liver fibrosis, a model wound healing system, is characterized by excessive deposition of extracellular matrix (ECM) in the liver. Although many fibrogenic cell types may express ECM, the hepatic stellate cell (HSC) is currently considered to be the major effector. HSCs transform into myofibroblast-like cells, also known as hepatic myofibroblasts in a process known as activation; this process is characterized in particular by de novo expression of smooth muscle alpha actin (SM α-actin) and type 1 collagen. The family of actins, which form the cell's cytoskeleton, are essential in many cellular processes. β-actin and cytoplasmic γ-actin (γ-actin) are ubiquitously expressed, whereas SM α-actin defines smooth muscle cell and myofibroblast phenotypes. Thus, SM α-actin is tightly associated with multiple functional properties. However, the regulatory mechanisms by which actin isoforms might regulate type 1 collagen remain unclear. In primary HSCs from normal and fibrotic rat liver, we demonstrate that myocardin, a canonical SRF cofactor, is upregulated in hepatic myofibroblasts and differentially regulates SM α-actin, γ-actin, and β-actins through activation of an ATTA box in the SM α-actin and a CCAAT box in γ-actin and β-actin promoters, respectively; moreover, myocardin differentially activated serum response factor (SRF) in CArG boxes of actin promoters. In addition, myocardin-stimulated Smad2 phosphorylation and RhoA expression, leading to increased expression of type 1 collagen in an actin cytoskeleton-dependent manner. Myocardin also directly enhanced SRF expression and stimulated collagen 1α1 and 1α2 promoter activities. In addition, overexpression of myocardin in vivo during carbon tetrachloride-induced liver injury led to increased HSC activation and fibrogenesis. In summary, our data suggest that myocardin plays a critical role in actin cytoskeletal dynamics during HSC activation, in turn, specifically regulating type I collagen expression in hepatic myofibroblasts. |
| Databáze: | OpenAIRE |
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