CELL-SHAPE-DEPENDENT MODULATION OF P52(PAI-1) GENE-EXPRESSION INVOLVES A SECONDARY RESPONSE PATHWAY

Expression of the rat p52(PAI-1) gene is positively regulated by agent s that influence cellular microfilament organization and/or cell-to-su bstrate adhesion [e.g. cytochalasin D (CD) and sodium n-butyrate (NaB) ] [Higgins, Chaudhari and Ryan (1991) Biochem. J. 273, 651-658; Higgin s, Ryan and Providence (1994) J. Cell. Physiol. 159, 187-195]. As shap e-responsive genes may be subject to inducer-specific controls, the bi ochemical mechanisms underlying the shape-dependent pathway of p52(PAI -1) gene regulation were examined in v-ras-transformed rat kidney (KNR K) cells. NaB and/or CD effectively stimulated p52(PAI-1) run-off tran scription and augmented de novo p52(PAI-1) mRNA and protein synthesis in KNRK cells; induction at both the mRNA and protein levels was inhib ited by actinomycin D. Pretreatment with cycloheximide (CX) markedly a ttenuated NaB- and/or CD-stimulated p52(PAI-1) expression. CX alone, h owever, induced low levels of p52(PAI-1) mRNA; increased p52(PAI-1) pr otein synthesis was evident after release of KNRK cells from CX blocka de. Such CX-mediated induction was also sensitive to actinomycin D. Fu ll stimulation of p52(PAI-1) expression in KNRK cells in response to t he shape modulators NaB and/or CD involves transcriptional activation of the p52(PAI-1) gene, requires de novo RNA synthesis and occurs thro ugh a secondary-response (i.e. protein-synthesis-dependent) pathway.