MLC激酶IKK2在NO/TNFα对机体血压调控中的作用和机制

Myosin light chain (MLC) phosphorylation at serine 19 (Ser19) determines the contractile state of vascular smooth muscle and thus total peripheral resistance and blood pressure. Although several kinases have been shown to be capable of phosphorylating MLC at Ser19, MLC kinase (MLCK) is the only one with an established role in intracellular MLC Ser19 phopshorylation. However, multiple studies, such as that MLCK deficient blood vessels remain contractility in response to elevated [Ca2+]i, have strongly indicated that in addition to MLCK, there is unidentified kinase(s) phosphorylates MLC Ser19 in vascular smooth muscle cells. Inhibitor κB kinase 2 (IKK2) was identified as a critical kinase in NF-κB activation through phosphorylating inhibitor κB (IκB) and consequently leading to its degradation and the release of bound NF-κB. Since then, IKK2 has been shown to phosphorylate multiple other substrates than IκB and be involved in multiple important cellular responses, such as proliferation, migration, insulin sensitivity, and et al. We recently observed that IKK2 inhibitors, including inhibitory peptide and chemicals, markedly relaxed vasoconstriction extra and in viva. Further studies revealed that in vitro phosphorylation reaction analysis showed that IKK2 was capable of time- and dose-dependently phosphorylating MLC. Kinetic analysis demonstrated the Km and Vmax of MLC phosphorylation by IKK2 was comparable to those of IκB phosphorylation by IKK2, strongly supporting that IKK2 may be an important intracellular MLCK. In the present proposal, we hypothesize that IKK2 regulates vasoconstriction and blood pressure as a MLC kinase and is involved in the vascular and blood pressure effects of TNFα and nitric oxide.

血管平滑肌细胞MLC第19号丝氨酸磷酸化对血管收缩和血压调节具有重要作用。我们的前期研究发现,IKK2是VSMC中一类重要的MLC激酶。其抑制剂对胸主动脉环收缩具有显著的抑制作用；IKK2对MLC体外磷酸化反应表现为时间和剂量依赖性；动力学Km值和Vmax值类似于IKK2对IkB磷酸化作用。炎症与血压变化具有相关性。IKK2/NF-kB途径对炎症因子的转录起着重要的作用。TNFα通过IKK2/NF-kB途径上调/NO通过蛋白巯基亚硝基化下调IKK2活性调控炎症反应，但是关于这种变化是否对血压具有调控作用尚未阐明。因此，我们推测："IKK2对MLC磷酸化作用介导了NO/TNFα对血管舒缩调控"是机体生理/病理生理过程血压调节的新机制。我们拟在细胞-血管环-整体层面应用siRNA、IKK2转染、体外磷酸化、免疫共沉淀和IKK2敲除小鼠等证明我们的假说。这将为高血压的防治提供新思路和新靶点。