Blockade of the Ras–Extracellular Signal–Regulated Kinase 1/2 Pathway Is Involved in Smooth Muscle 22α–Mediated Suppression of Vascular Smooth Muscle Cell Proliferation and Neointima Hyperplasia

Abstract

Objective-Vascular smooth muscle cells (VSMCs) can switch between differentiated and dedifferentiated phenotypes, and this phenotype switch is believed to be essential for repair of vascular injury. We studied the inhibitory effect of smooth muscle 22␣ (SM22␣) on VSMC proliferation in vitro and in vivo and explored the potential molecular mechanisms of this effect. Methods and Results-By using coimmunoprecipitation and glutathione S-transferase pull-down assays, we have shown that SM22␣ binds to Ras in SM22␣-overexpressed VSMCs in the presence or absence of platelet-derived growth factor-BB stimulation. SM22␣ arrested cell cycle progression through segregation of Ras with Raf-1 and downregulation of the Raf-1-MEK1/2-extracellular signal-regulated kinase 1/2 mitogen-activated protein kinase signaling cascade. The inhibitory effect of SM22␣ on VSMC proliferation was verified in vivo. The infection of rat carotid arteries with recombinant adenovirus encoding SM22␣ inhibited neointimal hyperplasia via suppression of the Raf-1-MEK1/ 2-extracellular signal-regulated kinase 1/2 signaling pathway. Conclusion-These findings suggest that high expression of SM22␣ inhibits cell proliferation via reduction of the response to mitogen stimuli in VSMCs and provide a novel mechanism by which VSMCs maintain their contractile phenotype and resist mitogenic stimuli in an SM22␣-dependent manner.

TRAF6-Mediated SM22α K21 Ubiquitination Promotes G6PD Activation and NADPH Production, Contributing to GSH Homeostasis and VSMC Survival In Vitro and In Vivo

“…[16][17][18] Here, we further identified that the expression of SM22α at both the mRNA and protein level was decreased in VSMCs after PDGF-BB stimulation for 3 and 12 hours (Online Figure II; Figure 2C). Furthermore, we recently found that SM22α was polyubiquitinated after 6 hours of PDGF-BB stimulation.…”

“…The increased numbers of BrdU-positive cells observed in the carotid arteries of SM22α −/− mice after ligation were decreased by reexpression of SM22α WT but not K21R mutant protein (Online Figure XF), although the PPP provides nucleotide precursors for cell proliferation, consistent with our previous findings. 16 Similarly, the percentage of TUNEL-stained cells also decreased under the same conditions ( Figure 6D). Furthermore, G6PD inhibition by 6-aminonicotinamide enhanced the inhibitory effect of SM22α on BrdU incorporation in carotid arteries from SM22α −/− mice after ligation ( Figure 6E; Online Figure XG and XH).…”

Small G Proteins in the Cardiovascular System: Physiological and Pathological Aspects

“…Such a regulation is responsible for the antiproliferative effect of the contractile phenotype marker SM22␣. SM22␣ binds Ras, resulting in downregulation of Ras-Raf-MAPK signaling and blockade of G 1 -S phase cycle progression in vascular smooth muscle cells (107). In vivo, this mechanism is responsible for SM22␣ overexpression-induced inhibition of neointimal hyperplasia induced by balloon injury (107).…”

“…SM22␣ binds Ras, resulting in downregulation of Ras-Raf-MAPK signaling and blockade of G 1 -S phase cycle progression in vascular smooth muscle cells (107). In vivo, this mechanism is responsible for SM22␣ overexpression-induced inhibition of neointimal hyperplasia induced by balloon injury (107). In the same way, R-Ras is a member of Ras protein family that antagonizes H-Ras signaling (88,438).…”

Acetylbritannilactone suppresses growth via upregulation of kr�ppel-like transcription factor 4 expression in HT-29 colorectal cancer cells

“…The protein expression for cyclinA, cyclinD1, cyclinE, CDK2, CDK4, CDK6, KLF4, p21, β-actin in HT-29 cells were examined by Western blot analysis as previously described (22). The blots were detected with the enhanced chemiluminescence detection system (Santa Cruz Biotechnology).…”