REGULATION OF GENE-EXPRESSION IN SERTOLI CELLS BY FOLLICLE-STIMULATING-HORMONE (FSH) - CLONING AND CHARACTERIZATION OF LRPR1, A PRIMARY RESPONSE GENE ENCODING A LEUCINE-RICH PROTEIN

Searching for hormone-regulated genes in testicular Sertoli cells, we cloned and sequenced a cDNA of 3108 base pairs, named LRPR1 (signifyin g leucine-rich primary response gene 1). This cDNA sequence has an ope n reading frame of 2238 base pairs encoding a leucine-rich protein of 746 amino acid residues with a relative molecular mass of 85.6 kDa. As much as 16% of the amino acid residues is leucine. Database analysis revealed significant similarity of LRPR1 to the human brain cDNA seque nce EST00443, but not to any other sequences present in databases. The expression of LRPR1 mRNA in Sertoli cells is strongly and rapidly up- regulated by follicle-stimulating hormone (FSH). The level of LRPR1 mR NA was very low in Sertoli cells isolated from 21-day-old rats and cul tured for 3 days in the absence of FSH, but LRPR1 mRNA expression was markedly increased within 2 h after addition of FSH to these cultures. A maximal response was reached within 4 h. Dibutyryl-cyclic AMP [(Bu) (2)cAMP] and forskolin had similar effects compared to FSH, indicating that cAMP acts as a second messenger in the regulation of LRPR1 expre ssion. The up-regulation of LRPR1 mRNA expression by FSH was also obse rved in the presence of the protein synthesis inhibitor cycloheximide, indicating that FSH regulates LRPR1 mRNA expression through a direct mechanism which does not require de novo protein synthesis. Thus, LRPR 1 represents a primary response gene in FSH action on Sertoli cells. T he presently available data indicate that LRPR1 mRNA expression is reg ulated specifically by FSH, since several other hormones and growth fa ctors did not affect LRPR1 mRNA expression in the cultured Sertoli cel ls. LRPR1 mRNA expression is relatively high in testis, ovary and sple en. A much lower mRNA level was found in brain and lung, and no expres sion was detected in liver, kidney, heart, muscle, pituitary gland, pr ostate, epididymis and seminal vesicle. The basal level of testicular LRPR1 expression in intact 21-day-old rats was markedly increased with in several hours after a single i.p. injection of FSH, indicating that in vivo LRPR1 mRNA expression may appear to be a useful parameter to evaluate testicular FSH action.