The plasminogen activator (PA), urokinase, (UK) plays an important role in tissue remodelling by mediating the conversion of plasminogen into the serine-protease, plasmin. UK can bind to a specific cell surface receptor which serves to accelerate plasminogen activation. The present study was undertaken to determine the effect of the chemical agent N,N-dimethylformamide (DMF), on the expression of UK and its receptor in a colon cancer cell line, CBS. DMF increased radioactive UK binding to CBS in a dose-dependent fashion. A level of 0.75% (v/v) has a maximal effect in this regard producing a 150% increase in the amount of radioligand bound. Crosslinking of a radioactive aminoterminal (ATF) of UK, corresponding to the receptor-binding sequence of the PA, to the surface of CBS cells indicated a radioactive complex of molecular mass 66 kDa. This binding could be abolished with an excess of unlabelled ATE The amount of this 66 kDa complex increased over an identical concentration range used to elevate radioligand binding in the receptor assays. Augmented radioligand binding to CBS cells, treated with DMF, was a consequence of an increase in the number of UK receptors from 7.6X 103 to 19.9 × 103 as determined by Scatchard analysis. Northern blotting for UK receptor transcript revealed that this increase in the amount of receptor binding protein was a consequence of a more abundant transcript. In contrast to the inductive effect on UK receptor expression, DMF, over an identical concentration range, suppressed, by up to 80%, the level of steady-state mRNA encoding the PA. Maximal suppression of UK mRNA occurred after 4 days suggesting that this effect of DMF was not coordinated with the induction of UK receptor expression which required only a 24h period. In conclusion, this is the first study to indicate a divergent effect of an agent, on the expression of UK and its receptor.
ASJC Scopus subject areas