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Simultaneous stimulation of urokinase and tissue‐type plasminogen activators by phorbol esters in human ovarian carcinoma cells
Author(s) -
Band Vimla,
Karlan Beth Y.,
Zurawski Vincent R.,
Littlefield Bruce A.
Publication year - 1989
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.1041380115
Subject(s) - protein kinase c , cycloheximide , stimulation , phorbol , secretion , endocrinology , medicine , tetradecanoylphorbol acetate , staurosporine , biology , diacylglycerol kinase , in vitro , microbiology and biotechnology , chemistry , protein biosynthesis , biochemistry , phosphorylation
OVCA 433 human ovarian carcinoma cells secrete both mammalian plasminogen activators (PAs) urokinase (UK) and tissue‐type PA (tPA). Treatment of cells with 4β‐phorbol‐12‐myristate‐13‐acetate (PMA), a stimulator of protein kinase C (PKC), leads to large increases in the secretion rates of both PA types. PA stimulation by PMA is time‐ and concentration‐dependent, with maximal effects occurring between 12 and 24 h at PMA concentrations of 1–10 ng/ml. The PMA effect is mimicked by mezerein, another known PKC stimulator, but not by 4α‐phorbol or 4α‐phorbol‐12,13‐didecanoate, two phorbol compounds that do not stimulate PKC. PA activity is virtually unaffected by 1‐oleoyl‐2‐acetylglycerol (OAG), a synthetic diacylglycerol that stimulates PKC in vitro but has variable effects on whole cells. PMA stimulation of PA activity is blocked by both actinomycin D and cycloheximide, indicating requirements for new RNA and protein synthesis. When analyzed individually, the relative PMA‐induced increases in UK and tPA activities are identical. Increased UK activity is fully accounted for by increased UK antigen secretion, whereas increased tPA secretion accounts for only about one‐half of the increased tPA activity. Similarly, PMA induces large increases in steady‐state UK mRNA levels, while its effects on tPA mRNA levels are only modest. Thus, while increases in secretion rates and mRNA levels can completely account for UK stimulation, other mechanisms augmenting these processes must exist specifically for tPA. Since the relative increases in UK and tPA activities are identical despite the probable existence of multiple mechanisms contributing to tPA regulation, our data suggest the possibility of interrelationships between the two pathways such that equivalent degrees of UK and tPA activity stimulation are ultimately achieved.