Rousseau Simon, Peggie Mark, Campbell David G, Nebreda Angel R, Cohen Philip
MRC Protein Phosphorylation Unit, Faculty of Life Sciences, University of Dundee, MSI/WTB Complex, Dow Street, Dundee DD1 5EH, Scotland, UK.
Biochem J. 2005 Oct 15;391(Pt 2):433-40. doi: 10.1042/BJ20050935.
The neurite outgrowth inhibitor protein Nogo is one of 300 proteins that contain a reticulon homology domain, which is responsible for their association with the endoplasmic reticulum. Here we have found that the Nogo-B spliceform becomes phosphorylated at Ser107 in response to lipopolysaccharide in RAW264 macrophages or anisomycin in HeLa cells. The phosphorylation is prevented by SB 203580, an inhibitor of SAPK2a (stress-activated protein kinase 2a)/p38a and SAPK2b/p38b, and does not occur in embryonic fibroblasts generated from SAPK2a/p38a-deficient mice. Nogo-B is phosphorylated at Ser107 in vitro by MAPKAP-K2 [MAPK (mitogen-activated protein kinase)-activated protein kinase-2] or MAPKAP-K3, but not by other protein kinases that are known to be activated by SAPK2a/p38a. The anisomycin-induced phosphorylation of Ser107 in HeLa cells can be prevented by 'knockdown' of MAPKAP-K2 using siRNA (small interfering RNA). Taken together, our results identify Nogo-B as a new physiological substrate of MAPKAP-K2.
神经突生长抑制蛋白Nogo是300种含有网状蛋白同源结构域的蛋白质之一,该结构域负责它们与内质网的结合。我们发现,在RAW264巨噬细胞中,Nogo-B剪接异构体在受到脂多糖刺激时,或在HeLa细胞中受到茴香霉素刺激时,会在Ser107位点发生磷酸化。这种磷酸化可被SB 203580(一种SAPK2a(应激激活蛋白激酶2a)/p38a和SAPK2b/p38b的抑制剂)阻止,并且在由SAPK2a/p38a缺陷小鼠产生的胚胎成纤维细胞中不会发生。在体外,Nogo-B可被MAPKAP-K2[丝裂原活化蛋白激酶(MAPK)激活的蛋白激酶-2]或MAPKAP-K3在Ser107位点磷酸化,但不会被其他已知可被SAPK2a/p38a激活的蛋白激酶磷酸化。使用小干扰RNA(siRNA)“敲低”MAPKAP-K2可阻止茴香霉素诱导的HeLa细胞中Ser107的磷酸化。综上所述,我们的结果确定Nogo-B是MAPKAP-K2的一种新的生理底物。