Okadaic acid strongly increases gene transcription, mRNA and protein level for the urokinase receptor in human A549 cells

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Abstract
The specific phosphatase inhibitor, okadaic acid, increases the level of mRNA for the receptor for urokinase-type plasminogen activator (u-PAR) in 8 out of 13 human cell lines. The strongest increase (90-fold) was observed in A549 lung carcinoma cells, in which it was partly traced back to an increased transcription of the u-PAR gene. There was a parallel but less pronounced increase in the u-PAR protein level. These findings indicate that u-PAR gene transcription is regulated by one or more factors that are constitutively phosphorylated and are dephosphorylated by okadaic acid-sensitive phosphatases. A lack of additivity of u-PAR induction by okadaic acid and by the protein kinase C activator, PMA, in the A549 cells suggests that the regulatory factors affected by okadaic acid are phosphorylated by protein kinase C