Protein kinase Cδ mediates MCP-1 mRNA stabilization in vascular smooth muscle cells

Abstract

Monocyte chemoattractant protein-1 (MCP-1) is an inflammatory chemokine that promotes atherosclerosis and is a mediator of the response to arterial injury. We previously demonstrated that platelet-derived growth factor (PDGF) and angiotensin II (Ang) induce the accumulation of MCP-1 mRNA in vascular smooth muscle cells mainly by increasing mRNA stability. In the present study, we have examined the signaling pathways involved in this stabilization of MCP-1 mRNA. The effect of PDGF (BB isoform) and Ang on MCP-1 mRNA stability was mediated by the PDGF β and angiotensin II receptor AT1R, respectively, and did not involve transactivation between the two receptors. The effect of PDGF-BB was blocked by inhibitors of protein kinase C (PKC), but not by inhibitors of phosphoinositol 3-kinase (PI3K), Src, or NADPH oxidase (NADPHox). In contrast, the effect of Ang was blocked by inhibitors of Src, and PKC, but not by inhibitors of PI3 K, or NADPHox. The effect of PDGF BB on MCP-1 mRNA stability was blocked by siRNA directed against PKCδ and protein kinase D (PKD), whereas the effect of Ang was blocked only by siRNA directed against PKCδ. These results suggest that the enhancement of MCP-1 mRNA stability by PDGF-BB and Ang are mediated by distinct "proximal" signaling pathways that converge on activation of PKCδ. This study identifies a novel role for PKCδ in mediating mRNA stability in smooth muscle cells.

Y-Box Binding Protein 1 and RNase UK114 Mediate Monocyte Chemoattractant Protein 1 mRNA Stability in Vascular Smooth Muscle Cells

“…Scrambled siRNA was purchased from Santa Cruz Biotechnology, Inc., as control siRNA-A (sc-37007), consisting of a scrambled sequence that will not lead to the specific degradation of any known cellular mRNA. SMCs, at 60% confluence, were transfected with 20 nM double-stranded siRNA using Oligofectamine (Invitrogen, Carlsbad, CA) (28). After 72 h, the cells were collected and analyzed for mRNA and protein using real-time PCR (RT-PCR) and Western blots, respectively.…”

Protein kinase D in vascular biology and angiogenesis

“…Ang II is a known hypertrophic factor in VSMC, and there is evidence that hypertrophy is mediated by PKD via two pathways that converge on the MEF2 transcription factor: PKD-dependent ERK5 phosphorylation, allowing it to enter the nucleus and activate MEF2 (38), and PKD-mediated phosphorylation of HDAC5, inducing its nuclear export and allowing MEF2 to activate transcription (37). PKD has also been implicated in PDGF, but not Ang II-mediated, monocyte chemoattractant protein-1 (MCP-1) mRNA stabilisation (39). The relatively small number of studies investigating PKD function in VSMCs have been largely limited to cultured cells, and there is a need for work investigating the role of PKDs in VSMC functions in vivo, both developmentally, for example, in the embryonic cardiovascular system, and in adult vascular physiology and disease.…”

Protein kinase C δ regulates the release of collagen type I from vascular smooth muscle cells via regulation of Cdc42

“…Studies of PKCδ knockout (KO) mice reveal that mice lacking PKCδ develop normally but exhibit an antiapoptotic phenotype when subjected to models of vascular injury such as vein graft or carotid artery ligation (Leitges et al , 2001; Bai et al , 2010; Yamanouchi et al , 2010). More recently, PKCδ was reported to be involved in the regulation of chemokine expression and consequently proinflammatory signaling (Liu et al , 2010). …”