Slomiany B L, Slomiany A
Research Center C875, Rutgers School of Dental Medicine Rutgers, The State University of New Jersey, 110 Bergen Street, PO Box 1709, Newark, NJ, 07103-2400, USA,
Inflammopharmacology. 2015 Jun;23(2-3):101-9. doi: 10.1007/s10787-015-0231-6. Epub 2015 Mar 22.
Membrane recruitment followed by targeted phosphorylation of specific Tyr and Ser residues and the interaction with Rac GTPases are the crucial parts of an elaborate mechanism of PLCγ2 activation essential for its role in linking the specific receptor responses to a variety of hormones and bacterial endotoxins with the intended intracellular targets. Here, we explored the involvement of Rac in mediation of PLCγ2 activation associated with gastric mucosal inflammatory responses to H. pylori LPS and the hormone, ghrelin. We show that stimulation of gastric mucosal cells with the LPS leads to the membrane translocation of Rac1 as well as PLCγ2, while the effect of ghrelin is manifested by elevation in the membrane PLCγ2 activation and suppression in Rac1 translocation. However, blocking the LPS-induced Rac1 translocation, while detrimental to the PLCγ2 activation, has no effect on its membrane translocation. We reveal further that PLCγ2, localized in the membrane in association with Rac1 following the LPS stimulation, exhibits a marked increase in phosphorylation on Ser, while the modulatory effect of ghrelin, manifested by a drop in Rac1 translocation, is associated with a distinct decrease in PLCγ2 phosphorylation on Ser. Thus, the results suggest that H. pylori-elicited increase in gastric mucosal PLCγ2 phosphorylation on Ser serves as an essential platform for Rac1 colocalization and amplification in PLCγ2 activation.
膜募集,随后特定酪氨酸和丝氨酸残基的靶向磷酸化以及与Rac GTP酶的相互作用,是PLCγ2激活精细机制的关键部分,这对于其将特定受体对多种激素和细菌内毒素的反应与预期的细胞内靶点联系起来的作用至关重要。在此,我们探讨了Rac在介导与幽门螺杆菌脂多糖(LPS)和胃饥饿素激素相关的胃黏膜炎症反应中PLCγ2激活的作用。我们发现,用LPS刺激胃黏膜细胞会导致Rac1以及PLCγ2的膜转位,而胃饥饿素的作用表现为膜PLCγ2激活增加和Rac1转位受到抑制。然而,阻断LPS诱导的Rac1转位,虽然对PLCγ2激活有害,但对其膜转位没有影响。我们进一步揭示,在LPS刺激后与Rac1结合定位于膜上的PLCγ2,其丝氨酸磷酸化显著增加,而胃饥饿素的调节作用表现为Rac1转位减少,这与PLCγ2丝氨酸磷酸化明显降低有关。因此,结果表明幽门螺杆菌引起的胃黏膜PLCγ2丝氨酸磷酸化增加是Rac1在PLCγ2激活中共定位和放大的重要平台。