Immortalized hippocampal cells contain functional luteinizing hormone/human chorionic gonadotropin receptors

We used immortalized HN33p cells as surrogates for hippocampal neurons to investigate the functional importance of luteinizing hormone (LH)/human chorionic gonadotropin (hCG) receptors. The use of various detection techniques demonstrated that HN33p cells contain LH/hCG receptor transcripts and receptor protein that can bind I-125-hCG. Culturing them with highly purified hCG resulted in a significant, although modest, dose-and time-dependent and hormone specific increase in steady state 5-lipoxygenase (5-LO) mRNA and protein levels. The studies on signaling revealed that treatment of HN33p cells with hCG resulted in a robust dose- and a time-dependent significant increase in media cyclic AMP levels. In addition, treatment with a protein kinase (PK)A inhibitor, isoquinolinesulfonamide (H-89), but not with a PKC inhibitor, bisindolylmaleimide (Bis), prevented hCG from increasing the 5-LO protein levels. Pretreatment of HN33p cells for 48 hrs with 2 mu M antisense, but not sense, phosphorothioate oligodeoxy-nucleotides (ODN) synthesized from mouse LH/hCG receptor sequence resulted in a dramatic decrease in LH/hCG receptor protein levels. In the antisense, but not in sense, ODN-treated cells, hCG was unable to increase cyclic AMP and 5-LO protein levels, suggesting that receptors are required for hCG to work in HN33p cells.