首页 | 本学科首页   官方微博 | 高级检索  
     


Phosphorylation of the cytoplasmic domain of the integrin CD18 chain by protein kinase C isoforms in leukocytes.
Authors:Susanna Fagerholm  Nick Morrice  Carl G Gahmberg  Philip Cohen
Affiliation:MRC Protein Phosphorylation Unit, MSI/WTB Complex, University of Dundee, Dow Street, Dundee DD1 5EH, Scotland, United Kingdom. susanna.fagerholm@helsinki.fi
Abstract:The CD11/CD18 (beta(2)) integrins are leukocyte-specific adhesion receptors, and their ability to bind ligands on other cells can be activated by extracellular stimuli. During cell activation, the CD18 chain is known to become phosphorylated on serine and functionally important threonine residues located in the intracellular C-terminal tail. Here, we identify catalytic domain fragments of protein kinase C (PKC) delta and PKCbetaI/II as the major protein kinases in leukocyte extracts that phosphorylate a peptide corresponding to the cytoplasmic tail of the integrin CD18 chain. The sites phosphorylated in vitro were identified as Ser-745 and Thr-758. PKCalpha and PKCeta also phosphorylated these residues, and PKCalpha additionally phosphorylated Thr-760. Ser-745, a novel site, was shown to become phosphorylated in T cells in response to phorbol ester stimulation. Ser-756, a residue not phosphorylated by PKC isoforms, also became phosphorylated in T cells after phorbol ester stimulation. When leukocyte extracts were subjected to affinity chromatography on agarose to which residues 751-761 of the CD18 chain phosphorylated at Thr-758 were bound covalently, the only proteins that bound specifically were identified as isoforms of 14-3-3 proteins. Thus, PKC-mediated phosphorylation of CD18 after cell stimulation could lead to the recruitment of 14-3-3 proteins to the activated integrin, which may play a role in regulating its adhesive state or ability to signal.
Keywords:
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号