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Formin homology domain-containing protein 1 regulates smooth muscle cell phenotype.

ABSTRACT: Our goal was to test whether formin homology protein 1 (FHOD1) plays a significant role in the regulation of smooth muscle cell (SMC) differentiation and, if so, whether Rho kinase (ROCK)-dependent phosphorylation in the diaphanous autoinhibitory domain is an important signaling mechanism that controls FHOD1 activity in SMC.FHOD1 is highly expressed in aortic SMCs and in tissues with a significant SMC component. Exogenous expression of constitutively active FHOD1, but not wild-type, strongly activated SMC-specific gene expression in 10T1/2 cells. Treatment of SMC with the RhoA activator sphingosine-1-phosphate increased FHOD1 phosphorylation at Thr1141, and this effect was completely prevented by inhibition of ROCK with Y-27632. Phosphomimetic mutations to ROCK target residues enhanced FHOD1 activity, suggesting that phosphorylation interferes with FHOD1 autoinhibition. Importantly, knockdown of FHOD1 in SMC strongly inhibited sphingosine-1-phosphate-dependent increases in SMC differentiation marker gene expression and actin polymerization, suggesting that FHOD1 plays a major role in RhoA-dependent signaling in SMC.Our results indicate that FHOD1 is a critical regulator of SMC phenotype and is regulated by ROCK-dependent phosphorylation. Thus, additional studies on the role of FHOD1 during development and the progression of cardiovascular disease will be important.

SUBMITTER: Staus DP

PROVIDER: S-EPMC3025477 | biostudies-literature | 2011 Feb

REPOSITORIES: biostudies-literature

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Formin homology domain-containing protein 1 regulates smooth muscle cell phenotype.

Staus Dean P DP Blaker Alicia L AL Medlin Matt D MD Taylor Joan M JM Mack Christopher P CP

Arteriosclerosis, thrombosis, and vascular biology 20101124 2

<h4>Objective</h4>Our goal was to test whether formin homology protein 1 (FHOD1) plays a significant role in the regulation of smooth muscle cell (SMC) differentiation and, if so, whether Rho kinase (ROCK)-dependent phosphorylation in the diaphanous autoinhibitory domain is an important signaling mechanism that controls FHOD1 activity in SMC.<h4>Methods and results</h4>FHOD1 is highly expressed in aortic SMCs and in tissues with a significant SMC component. Exogenous expression of constitutively ...[more]

PMID: 21106951

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Project description:ObjectiveWe examined the role of syndecan-1 in modulating the phenotype of vascular smooth muscle cells in the context of endogenous inflammatory factors and altered microenvironments that occur in disease or injury-induced vascular remodeling.Methods and resultsVascular smooth muscle cells (vSMCs) display a continuum of phenotypes that can be altered during vascular remodeling. While the syndecans have emerged as powerful and complex regulators of cell function, their role in controlling vSMC phenotype is unknown. Here, we isolated vSMCs from wild type (WT) and syndecan-1 knockout (S1KO) mice. Gene expression and western blotting studies indicated decreased levels of α-smooth muscle actin (α-SMA), calponin, and other vSMC-specific differentiation markers in S1KO relative to WT cells. The spread area of the S1KO cells was found to be greater than WT cells, with a corresponding increase in focal adhesion formation, Src phosphorylation, and alterations in actin cytoskeletal arrangement. In addition, S1KO led to increased S6RP phosphorylation and decreased AKT and PKC-α phosphorylation. To examine whether these changes were present in vivo, isolated aortae from aged WT and S1KO mice were stained for calponin. Consistent with our in-vitro findings, the WT mice aortae stained higher for calponin relative to S1KO. When exposed to the inflammatory cytokine TNF-α, WT vSMCs had an 80% reduction in syndecan-1 expression. Further, with TNF-α, S1KO vSMCs produced increased pro-inflammatory cytokines relative to WT. Finally, inhibition of interactions between syndecan-1 and integrins αvβ3 and αvβ5 using the inhibitory peptide synstatin appeared to have similar effects on vSMCs as knocking out syndecan-1, with decreased expression of vSMC differentiation markers and increased expression of inflammatory cytokines, receptors, and osteopontin.ConclusionsTaken together, our results support that syndecan-1 promotes vSMC differentiation and quiescence. Thus, the presence of syndecan-1 would have a protective effect against vSMC dedifferentiation and this activity is linked to interactions with integrins αvβ3 and αvβ5.

Project description:Smooth muscle cells are maintained in a differentiated state in the vessel wall, but can be modulated to a synthetic phenotype following injury. Smooth muscle phenotypic modulation is thought to play an important role in the pathology of vascular occlusive diseases. Phenotypically modulated smooth muscle cells exhibit increased proliferative and migratory properties that accompany the downregulation of smooth muscle cell marker proteins. Extracellular matrix proteins, including fibronectin, can regulate the smooth muscle phenotype when used as adhesive substrates. However, cells produce and organize a 3-dimensional fibrillar extracellular matrix, which can affect cell behavior in distinct ways from the protomeric 2-dimensional matrix proteins that are used as adhesive substrates. We previously showed that the deposition/polymerization of fibronectin into the extracellular matrix can regulate the deposition and organization of other extracellular matrix molecules in vitro. Further, our published data show that the presence of a fibronectin polymerization inhibitor results in increased expression of smooth muscle cell differentiation proteins and inhibits vascular remodeling in vivo. In this manuscript, we used an in vitro cell culture system to determine the mechanism by which fibronectin polymerization affects smooth muscle phenotypic modulation. Our data show that fibronectin polymerization decreases the mRNA levels of multiple smooth muscle differentiation genes, and downregulates the levels of smooth muscle ?-actin and calponin proteins by a Rac1-dependent mechanism. The expression of smooth muscle genes is transcriptionally regulated by fibronectin polymerization, as evidenced by the increased activity of luciferase reporter constructs in the presence of a fibronectin polymerization inhibitor. Fibronectin polymerization also promotes smooth muscle cell growth, and decreases the levels of actin stress fibers. These data define a Rac1-dependent pathway wherein fibronectin polymerization promotes the SMC synthetic phenotype by modulating the expression of smooth muscle cell differentiation proteins.

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Formin homology domain-containing protein 1 regulates smooth muscle cell phenotype.

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Formin homology domain-containing protein 1 regulates smooth muscle cell phenotype.

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