TYROSINE PHOSPHORYLATION IS CRUCIAL FOR GROWTH SIGNALING BY TISSUE INHIBITORS OF METALLOPROTEINASES (TIMP-1 AND TIMP-2)

[H-3]Thymidine (TdR) incorporation by human osteosarcoma cell line MG- 63 was significantly stimulated at as early as 3 h after the addition of either TIMP-1 or TIMP-2 alone, Maximum stimulation was attained at a concentration of either 20 ng/ml (0.71 nM) TIMP-1 or 1.0 ng/ml (46 p M) TIMP-2. Tyrosine kinase inhibitors such as genistein, erbstatin, an d herbimycin A almost completely inhibited the [H-3]TdR incorporation stimulated by either of the TIMPs, However, essentially no effect was observed with H-89, H-7, bisindolylmaleimide and K-252a, These inhibit ion studies suggest a crucial role for tyrosine kinase in the signal t ransduction of TIMPs. Phosphotyrosine-containing proteins were signifi cantly elevated by the treatment with both TIMPs. We also found that e ither TIMP stimulated an increase in mitogen-activated protein (MAP) k inase activity, suggesting that MAP kinase plays a role in TIMP-depend ent growth signaling.