Transcriptional regulation of Pim-1 kinase in vascular smooth muscle cells and its role for proliferation

Abstract

The Ser/Thr-protein kinase Pim-1 has been discovered as a novel transducer of survival- and cell cycle promoting signals in the hematopoietic cell system. Although its significance for proliferation of vascular smooth muscle cells (VSMC) in vitro and neointima formation in vivo has been suggested recently, the mechanism has barely been characterized. This study aimed to foster the understanding of Pim-1 expression and regulation in murine VSMC in response to factors typically present within the atherosclerotic plaque. While oxidative stress, VEGF-A165 and angiotensin II did not have any effect on Pim-1 expression, VSMC strongly increased (3-fold) Pim-1 mRNA upon stimulation with PDGF(bb), followed by its protein upregulation. Half life of Pim-1 RNA and protein were determined to be 25 min and 6 h, respectively. PDGF(bb) induced a strong, 10-fold increase in BrdU-uptake, a marker of proliferation. This was effectively blocked by either Pim-1-specific inhibitor quercetagetin or adenovirally introduced Pim-1 shRNA. We further identified the signaling pathways linking PDGF(bb) to Pim-1 in VSMC: as expected, we determined transcriptional stimulation of Pim-1 via Janus-activated kinase (Jak), but also an additional pathway involving protein kinase C (PKC) and the mitogen-activated protein kinase Mek1/2. Blockade of Akt signaling did, however, not interfere with Pim-1 upregulation, suggesting an independence of either survival system. PDGF(bb)-induced proliferation of VSMC is partly attributed to transcriptionally upregulated Pim-1 and was assigned to distinct cell signaling. Our findings help to understand the fundamental processes of vasculoproliferative diseases thus opening avenues for its prevention and treatment.

Cell-specific and hypoxia-dependent regulation of human HIF-3α: inhibition of the expression of HIF target genes in vascular cells

“…Western blot analysis was performed as described previously [31] using the following antibodies and dilutions: mouse monoclonal anti-HIF-1a (BD Biosciences, Germany) 1:500; rabbit polyclonal anti-HIF-2a (Novus Biologicals, USA) 1:1,000; rabbit polyclonal HIF-3a (ab10134, Abcam, UK) 1:1,000; mouse anti-b-actin (Santa Cruz, USA) 1:1,000; sheep anti-mouse-HRP (GE Healthcare, USA) 1:10,000; goat anti-rabbit-HRP (Santa Cruz, USA) 1:2,500. Intensities of protein bands were estimated with ''Quantity One'' software from BioRad (USA).…”

Pim-1 is up-regulated by shear stress and is involved in shear stress-induced proliferation of rat mesenchymal stem cells

“…Such research has thus far been conducted in the hematopoietic cell system (Mikkers et al 2004;Stout et al 2004) and vascular cells (Willert et al 2010), where signal transduction for the initiation of Pim-1 transcription is followed by cytokine stimulation. In this study, SS mediated a long-term effect on the induction of Pim-1 in rat MSCs for at least 12 h, demonstrating that the increase in Pim-1 gene expression level induced by SS was not transient.…”

“…Several reports have suggested that MAPKs can modulate the expression of Pim-1 (Aksoy et al 2007;Hu et al 2009;Willert et al 2010). It has also been reported that fluid flow activates MAPKs (Fitzgerald et al 2008;Wu et al 2006).…”

“…Previous studies (Aksoy et al 2007;Willert et al 2010;Zippo et al 2004) have suggested a relationship between Pim-1 and cell proliferation. To determine whether Pim-1 is involved in SS-induced MSC proliferation, detailed studies by RNA interference were carried out.…”

A pivotal role for Pim-1 kinase in esophageal squamous cell carcinoma involving cell apoptosis induced by reducing Akt phosphorylation

“…More and more evidence has demonstrated that Pim-1, a proto-oncogene encoding a serine/threonine protein kinase, plays an essential role in cell survival, cell proliferation, cell differentiation, cell cycle, and cell apoptosis (7)(8)(9)(10)(11)(12)(13)(14), especially in the occurrence and development of tumors (15)(16)(17)(18)(19)(20). Therefore, the rapidly increasing knowledge on the role of the Pim-1 in cancer will hopefully provide useful molecular markers for detection and prognosis of tumor.…”