Glycogen synthase kinase 3 beta positively regulates Notch signaling in vascular smooth muscle cells: role in cell proliferation and survival

Abstract

The role of glycogen synthase kinase 3 beta (GSK-3β) in modulating Notch control of vascular smooth muscle cell (vSMC) growth (proliferation and apoptosis) was examined in vitro under varying conditions of cyclic strain and validated in vivo following changes in medial tension and stress. Modulation of GSK-3β in vSMC following ectopic expression of constitutively active GSK-3β, siRNA knockdown and pharmacological inhibition with SB-216763 demonstrated that GSK-3β positively regulates Notch intracellular domain expression, CBF-1/RBP-Jκ transactivation and downstream target gene mRNA levels, while concomitantly promoting vSMC proliferation and inhibiting apoptosis. In contrast, inhibition of GSK-3β attenuated Notch signaling and decreased vSMC proliferation and survival. Exposure of vSMC to cyclic strain environments in vitro using both a Flexercell™ Tension system and a novel Sylgard™ phantom vessel following bare metal stent implantation revealed that cyclic strain inhibits GSK-3β activity independent of p42/p44 MAPK and p38 activation concomitant with reduced Notch signaling and decreased vSMC proliferation and survival. Exposure of vSMC to changes in medial strain microenvironments in vivo following carotid artery ligation revealed that enhanced GSK-3β activity was predominantly localized to medial and neointimal vSMC concomitant with increased Notch signaling, proliferating nuclear antigen and decreased Bax expression, respectively, as vascular remodeling progressed. GSK-3β is an important modulator of Notch signaling leading to altered vSMC cell growth where low strain/tension microenvironments prevail.

PI3K/mTOR inhibition upregulates NOTCH-MYC signalling leading to an impaired cytotoxic response

“…8 Previous work has suggested both positive and negative interactions between the two pathways mediated by GSK3. [50][51][52][53] Active forms of Akt have been reported to phosphorylate and inhibit NICD nuclear localisation 54 and it has been suggested that the PI3K-regulated kinase SGK can enhance FBXW7-mediated degradation of NICD; 55 therefore, blockade of PI3K signalling would be predicted to lead to increased levels of active NOTCH, as seen in our work.…”

Inhibitory phosphorylation of GSK-3β by AKT, PKA, and PI3K contributes to high NaCl-induced activation of the transcription factor NFAT5 (TonEBP/OREBP)

“…We conclude that the stimulatory effect of p38␣ on NFAT5 is not mediated by inhibition of GSK-3␤. Along the same line, inhibition of GSK-3␤ is also independent of p38 in cyclic strain of vascular smooth muscle cells (25). Although previous studies showed that AKT1 can act upstream of p38 (38), we and others demonstrated that wortmannin and triciribine have no significant effect on high NaCl-induced stimulatory phosphorylation of p38 (Fig.…”

Glycogen synthase kinase-3 beta (GSK-3β) signaling: Implications for Parkinson's disease

“…Although glycogen synthase kinase-3 (GSK-3) was originally Q2 named for its ability to phosphorylate glycogen synthase and regulate glucose metabolism [1,2], this multifunctional kinase was subsequently found to be a critical component in numerous cellular functions including regulation of different cell signaling [3], cell division [4], differentiation, proliferation and growth [5,6] as well as apoptosis [7]. In addition, accumulating evidences recently suggested that GSK-3 signaling pathway play key roles in the regulation of different aspects of neural development, such as neurogenesis, proliferation and neural differentiation [8,9].…”