Journal of Biological Chemistry
Volume 273, Issue 8, 20 February 1998, Pages 4660-4665
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NUCLEIC ACIDS, PROTEIN SYNTHESIS, AND MOLECULAR GENETICS
Identification of the Phosphatidic Acid Phosphatase Type 2a Isozyme as an Androgen-regulated Gene in the Human Prostatic Adenocarcinoma Cell Line LNCaP*

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Differential display was used to identify novel androgen-regulated genes in the human prostatic adenocarcinoma cell line LNCaP. A 322-base pair cDNA fragment that was consistently induced by the synthetic androgen R1881 revealed 100% homology with the human phosphatidic acid phosphatase type 2a isozyme very recently reported by Kai et al. (PAP-2a; Kai., M., Wada, I., Imai, S.-i., Sakane, F., and Kanoh, H. (1997) J. Biol. Chem.272, 24572–24578). The fragment was used to clone the corresponding cDNA from a human prostate library. The deduced amino acid sequence confirmed the identity with human PAP-2a. The inducibility of PAP-2a mRNA by androgens was confirmed by Northern blot hybridization. The effect was time- and dose-dependent with a maximal stimulation (4-fold) after 24 h of treatment with 10−9m R1881. The steroid specificity of PAP-2a mRNA regulation was found to be in agreement with the aberrant ligand specificity of the mutated androgen receptor in LNCaP cells, supporting the involvement of the androgen receptor in the induction process. Furthermore, low basal levels of PAP-2a mRNA and absence of androgen inducibility were observed in the poorly differentiated and androgen receptor-negative cell lines PC-3 and DU-145. Induction of PAP-2a mRNA was not affected by the protein synthesis inhibitor cycloheximide and was accompanied by a marked increase in PAP-2 activity as measured by the conversion of phosphatidic acid into diacylglycerol in membrane fractions of LNCaP. Comparison of the expression of PAP-2a mRNA in 50 different human tissues revealed ubiquitous expression. The highest levels, however, were observed in the prostate. Since PAP-2 plays a pivotal role in the control of signal transduction by lipid mediators such as phosphatidate, lysophosphatidate, and ceramide-1-phosphate, the ability of androgens to stimulate the expression and activity of this enzyme in prostatic cells may provide an important opportunity for cross-talk between signaling pathways involving lipid mediators and androgens.

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*

This work was supported by grants from the Geconcerteerde Onderzoeksactie van de Vlaamse Gemeenschap, Grant 3.0048.94 from the Fund for Scientific Research, Flanders (Belgium) (Fonds voor Wetenschappelijk Ondersoek-Vlaanderen), grants from the Interuniversity Poles of Attraction Program, Belgian State, Prime Minister's Office, Federal Office for Scientific, Technical and Cultural Affairs, and the Vereniging voor Kankerbestrijding.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 reported in this paper has been submitted to EMBL, GenBank, and DDBJ data bases with accession number Y14436.

Senior Research Assistant of the Fund for Scientific Research-Flanders (Belgium) (F. W. O.).