PHORBOL ESTER STIMULATES THE ACTIVITY OF A PROTEIN-TYROSINE-PHOSPHATASE CONTAINING SH(2) DOMAINS (PTP1C) IN HL-60 LEUKEMIA-CELLS BY INCREASING GENE-EXPRESSION

The affinity-purified antibody to a protein tyrosine phosphatase (PTP) containing two src homology 2 domains (PTP1C) was generated. The anti body recognized two types of PTP1C (PTP1C-alpha and -beta) of which th e molecular sizes were 66 (alpha) and 62 kDa (beta), respectively, and these two types were expressed differentially in various cell types. The immune complex phosphatase assay using the antibody demonstrated t hat 12-O-tetradecanoylphorbol-13-acetate (TPA) and a vitamin D metabol ite increased the PTP activity of immunoprecipitated PTP1C to 230 and 150% of control, respectively. By contrast, neither dimethyl sulfoxide nor retinoic acid significantly affected the PTP activity of PTP1C in HL-60 cells. The time course increment by TPA of PTP1C activity was c losely correlated with that of the acquisition by HL-60 cells of a mac rophage-like phenotype. In addition, TPA increased the amount of PTP1C detected by immunoblotting and immunoprecipitation and raised the lev el of expression of PTP1C mRNA in HL-60 cells. The increase of PTP1C m RNA induced by TPA treatment was inhibited by cycloheximide, suggestin g that new protein synthesis is required for the increase by TPA of PT P1C mRNA expression. Furthermore, TPA increased the rate of transcript ion of the PTP1C gene without affecting the stability of PTP1C mRNA. T hese results suggest that (i) two subtypes of PTP1C may exist and func tion in various cell types, and (ii) TPA stimulates the PTP activity o f PTP1C by increasing the transcription rate of PTP1C gene expression. The possible role of PTP1C in the macrophage differentiation will be also discussed.