Crkl is constitutively tyrosine phosphorylated in platelets from chronic myelogenous leukemia patients and inducibly phosphorylated in normal platelets stimulated by thrombopoietin

Atsushi Oda, Yoshitaka Miyakawa, Brian J. Druker, Akaru Ishida, Katsutoshi Ozaki, Hideya Ohashi, Masatoshi Wakui, Makoto Handa, Kiyoaki Watanabe, Shinichiro Okamoto, Yasuo Ikeda

研究成果: Article査読

47 被引用数 (Scopus)

抄録

Platelet functions such as aggregation and clot retraction are often abnormal in chronic myelogenous leukemia (CML) patients. However, the molecular mechanisms of these altered functions are unknown. As expression of the p210(bcr-abl) oncogene product, a constitutively active tyrosine kinase, is known to have an essential role in the pathogenesis of CML and tyrosine phosphorylation is intimately involved in various aspects of platelet activation, we examined the pattern of protein tyrosine phosphorylation in platelets from 15 CML patients by immunoblotting with a monoclonal antiphosphotyrosine antibody (4G10). Before and after stimulation with thrombin, the only consistent difference between normal and CML platelets was the presence of a tyrosine phosphorylated protein with a relative molecular weight of 39 kD. This tyrosine phosphorylated protein was identified as crkl, an SH2, SH3 containing adapter protein. Thus, as previously demonstrated for neutrophils from CML patients, tyrosine phosphorylation of p39crkl persists in mature platelets. No tyrosine phosphorylation of crkl was detected following stimulation with thrombin in normal platelets. However, crkl became incorporated into the Triton X-100 insoluble residue following thrombin stimulation in a manner dependent on platelet aggregation. Further, we found that crkl is an endogenous substrate for calpain, a protease that may be involved in postaggregation signaling processes. This suggests that crkl may be involved in the reorganization of the cytoskeleton during normal platelet aggregation and its tyrosine phosphorylation in CML platelets may contribute to the abnormal platelet function in CML patients. Finally, we found that thrombopoietin induces tyrosine phosphorylation of crkl in normal platelets and FDCP cells genetically engineered to express human c-Mpl. This suggests that crkl can be phosphorylated by a kinase other than p210(bcr-abl) and that crkl may have a role in signaling by thrombopoietin.

本文言語English
ページ(範囲)4304-4313
ページ数10
ジャーナルBlood
88
11
DOI
出版ステータスPublished - 1996 12 1
外部発表はい

ASJC Scopus subject areas

  • 生化学
  • 免疫学
  • 血液学
  • 細胞生物学

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