COORDINATE GENE-EXPRESSION OF LUTEINIZING-HORMONE-RELEASING HORMONE (LHRH) AND THE LHRH-RECEPTOR AFTER PROLACTIN STIMULATION IN THE RAT NB2T-CELL LINE - IMPLICATIONS FOR A ROLE IN IMMUNOMODULATION AND CELL-CYCLE GENE-EXPRESSION

PRL has been shown to induce a number of genes after the stimulation o f quiescent Nb2 T-cells, including c-fos, c-myc, ornithine decarboxyla se, interferon regulatory factor-1, and others. One of these genes, LH RH, has not previously been reported to respond in this manner, althou gh we and others have reported its presence in rat and human T- and B- cells. Furthermore, recent evidence suggests that LHRH functions as an immunoregulator in a cytokine-like manner. Using the rat immature T-c ell line Nb2, we present data showing for the first time that 1) the L HRH gene is regulated by PRL at various times during the cell cycle; 2 ) an alternatively spliced LHRH messenger RNA exists in Nb2 cells and may produce a new truncated GnRH-associated peptide (alternatively cal led PIF for PRL-inhibiting factor); 3) the LHRH receptor is expressed in lymphocytes in a manner similar to the LHRH gene after PRL. additio n, and its complementary DNA sequence is identical to that of the pitu itary receptor; 5) the SH gene, found on the opposite strand of the LH RH gene, is expressed in lymphocytes at the same time and in the same manner as the LHRH gene; 6) the LHRH messenger RNA has a very short ha lf-life in these cells; and 7) the lymphocyte LHRH transcription start site is es; sentially the same as the hypothalamic site. These data s trengthen the relationship between PRL and LHRH expression in the immu ne system and further support our contention that LHRH is an important immunoregulator, on par with other known cytokines.