Tyrosine phosphorylation of the c-cbl proto-oncogene product mediated by cell surface antigen CD38 in HL-60 cells

Abstract

The human cell surface antigen CD38 is a 46-kDa type II transmembrane glycoprotein with a short N-terminal cytoplasmic domain and a long Cys-rich C-terminal extracellular one. We demonstrated previously that the extracellular domain of CD38 has NAD+ glycohydrolase (NADase) activity and that the ecto-form NADase activity induced in HL-60 cells during cell differentiation by retinoic acid is due to CD38. In the present study, we investigated the intracellular signaling mediated by CD38 in retinoic acid- differentiated HL-60 cells with an anti-CD38 monoclonal antibody. The addition of antiCD38 monoclonal antibody to the cells induced rapid tyrosine phosphorylation of the cellular proteins with molecular weights of 120,000, 87,000, and 77,000. An increase in tyrosine kinase activity in the anti- phosphotyrosine immunoprecipitates of the cells was also observed after the addition of anti-CD38 monoclonal antibody. Moreover, one of the prominent tyrosine-phosphorylated proteins stimulated by the anti-CD38 monoclonal antibody was identified as the c-cbl protooncogene product, p120(c-cbl). These results indicated that tyrosine phosphorylation of cellular proteins, including p120(c-cbl), is possibly involved in transmembrane signaling mediated by CD38.