Journal of Biological Chemistry
Volume 274, Issue 45, 5 November 1999, Pages 32333-32341
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CELL BIOLOGY AND METABOLISM
p42/44 MAP Kinase-dependent and -independent Signaling Pathways Regulate Caveolin-1 Gene Expression: ACTIVATION OF RAS-MAP KINASE AND PROTEIN KINASE A SIGNALING CASCADES TRANSCRIPTIONALLY DOWN-REGULATES CAVEOLIN-1 PROMOTER ACTIVITY*

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Caveolin-1 is a principal component of caveolae membranes in vivo. Caveolin-1 mRNA and protein expression are down-regulated in NIH 3T3 cells in response to transformation by activated oncogenes, such as H-Ras(G12V) and v-Abl. The mechanisms governing this down-regulation event remain unknown. Here, we show that caveolin-1 gene expression is directly regulated by activation of the Ras-p42/44 MAP kinase cascade. Down regulation of caveolin-1 protein expression by Ras is independent of (i) the type of activating mutation (G12V versus Q61L) and (ii) the form of activated Ras transfected (H-Ras versus K-Rasversus N-Ras). Treatment of Ras or Raf-transformed NIH 3T3 cells with a well characterized MEK inhibitor (PD 98059) restores caveolin-1 protein expression. In contrast, treatment of v-Src and v-Abl transformed NIH 3T3 cells with PD 98059 does not restore caveolin-1 expression. Thus, there must be at least two pathways for down-regulating caveolin-1 expression: one that is p42/44 MAP kinase-dependent and another that is p42/44 MAP kinase-independent. We focused our efforts on the p42/44 MAP kinase-dependent pathway. The activity of a panel of caveolin-1 promoter constructs was evaluated using transient expression in H-Ras(G12V) transformed NIH 3T3 cells. We show that caveolin-1 promoter activity is up-regulated ∼5-fold by inhibition of the p42/44 MAP kinase cascade. Using electrophoretic mobility shift assays we provide evidence that the caveolin-1 promoter (from −156 to −561) is differentially bound by transcription factors in normal and H-Ras(G12V)-transformed cells. We also show that activation of protein kinase A (PKA) signaling is sufficient to down-regulate caveolin-1 protein expression and promoter activity. Thus, we have identified two signaling pathways (Ras-p42/44 MAP kinase and PKA) that transcriptionally down-regulate caveolin-1 gene expression.

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This work was supported in part by National Institutes of Health, NCI Grant R01-CA-80250 (to M. P. L.), and grants from the Charles E. Culpeper Foundation (to M. P. L.), the G. Harold and Leila Y. Mathers Charitable Foundation (to M. P. L.), and the Sidney Kimmel Foundation for Cancer Research (to M. P. L.).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

The nucleotide sequence(s) reported in this paper has been submitted to the GenBank™/EMBL Data Bank with accession number(s) .

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Supported by National Institutes of Health Medical Scientist Training Program Grant T32-GM07288.

Supported in part by National Institutes of Health Grants R29-CA70897, R01-CA75503, and P50-HL56399 and recipient of the Irma T. Hirschl award and an award from the Susan G. Komen Breast Cancer Foundation.