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1,25‐dihydroxyvitamin D 3 regulates pp60 c‐src activity and expression of a pp60 c‐src activating phosphatase
Author(s) -
Chappel Jean,
Ross F. Patrick,
AbuAmer Yousef,
Shaw Andrey,
Teitelbaum Steven L.
Publication year - 1997
Publication title -
journal of cellular biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.028
H-Index - 165
eISSN - 1097-4644
pISSN - 0730-2312
DOI - 10.1002/(sici)1097-4644(19971215)67:4<432::aid-jcb2>3.0.co;2-t
Subject(s) - proto oncogene tyrosine protein kinase src , autophosphorylation , tyrosine kinase , biology , dephosphorylation , phosphorylation , kinase , biochemistry , microbiology and biotechnology , phosphatase , protein tyrosine phosphatase , tyrosine , protein kinase a , signal transduction
The nonreceptor tyrosine kinase, c‐src, and the steroid hormone, 1,25‐dihydroxyvitamin D 3 (1,25(OH) 2 D 3 ), are essential to development of the osteoclast phenotype. On the other hand, functional relationships between the activities of c‐src and 1,25(OH) 2 D 3 are as yet unknown. To determine if 1,25(OH) 2 D 3 modulates c‐src in osteoclastogenesis, we tested the steroid's effect on avian marrow‐derived osteoclast precursors. We find c‐src mRNA and immunoprecipitable c‐src protein (pp60 c‐src ) unaltered by 72 h exposure of these cells to 1,25(OH) 2 D 3 (10 −11 to 10 −9 M). Despite no quantitative change in pp60 c‐src , in vitro kinase assay of the immune complex reveals 1,25(OH) 2 D 3 dose‐dependently accelerates the catalytic activity of pp60 c‐src , enhancing its autophosphorylation and phosphorylation of exogenous substrate. This observation represents the first documentation, in nontransformed cells, of humoral induction of pp60 c‐src kinase. Consistent with the fact pp60 c‐src is activated by dephosphorylation of tyrosine 527 (Y527), the phosphotyrosine content of the pp60 c‐src immunoprecipitate, measured by immunoblot, is decreased by 1,25(OH) 2 D 3 . Alternatively, mRNA and protein levels of c‐src kinase (CSK), which inactivates pp60 c‐src by phosphorylating Y527, are not altered by the steroid. In contrast, 1,25(OH) 2 D 3 enhances mRNA and especially protein levels of avian protein tyrosine phosphatase λ (PTPλ), an enzyme specifically activating pp60 c‐src by dephosphorylating Y527 [Fang et al. (1994): J Biol Chem 269:20194–20200]. Thus, treatment of avian osteoclast precursors with 1,25(OH) 2 D 3 accelerates the catalytic activity of pp60 c‐src independent of protein expression. Activation of the kinase may occur via the Y527 dephosphorylating enzyme PTP, expression of which, we show for the first time, is regulated. J. Cell. Biochem. 67:432–438, 1997. © 1997 Wiley‐Liss, Inc.