Regulation of Transfected Glycoprotein Hormone α-Gene Expression in Primary Pituitary Cell Cultures

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Abstract
Studies of gene regulation are greatly facilitated by the ability to transfect DNA into cultured cells. We examined a variety of transfection techniques to optimize transient expression of the human glycoprotein hormone .alpha.-gene in primary pituitary cells and subsequently investigated the regulation of .alpha.-promoter transcription. Expression vectors driven by either the rous sarcoma virus-chloramphenicol acetyl transferase (RSVCAT) or the human .alpha.-gene (.alpha.CAT) promoters were transfected into cultures of dispersed female rat pituitary cells using calcium phosphate (CaPO4), diethylaminoethyl-dextran, lipofection, and electroporation procedures. CAT activity was optimal using the CaPO4 technique, resulting in 511 .+-. 49% and 57 .+-. 5% conversion/100 .mu.g protein/4 h for RSVCAT and .alpha.CAT, respectively. Immunohistochemical analyses of .alpha.CAT expression using anti-CAT monoclonal antibodies demonstrated that the .alpha.-gene promoter is expressed in pituitary cells, predominantly if not exclusively, in gonadotropes and thyrotropes. Hormonal regulation of .alpha.-promoter activity was assessed using both the CAT and the luciferase (LUC) reporter systems. .alpha.-Promoter activity was significantly (P < 0.001) stimulated by 8-bromo-cAMP (217% increase), GnRH (75% increase), GnRH agonist analog (141% increase), and TRH (75% increase). The expression of control plasmids (RSVLUC, TKLUC, pOLUC) was not affected by treatment with these agents. We conclude that CaPO4-mediated transfection allows analyses of transient gene expression in primary pituitary cells. The .alpha.-promoter directs expression specifically in pituitary cells, predominantly gonadotropes and thyrotropes. .alpha.-Gene transcription is stimulated by GnRH, TRH, and 8-bromo-cAMP.

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