Human Choriogonadotropin Signaling in Cell Proliferation

Summary

Principal Investigator: MICHAEL S HUDECKI
Abstract: hCG plays a key role in human reproduction and is produced during the first trimester of pregnancy. It is also produced by a variety of tumors including choriocarcinoma, hydatidiform mole, and embryonic carcinoma of the testis. Structurally, hCG is similar in some respects to tumor growth factor (TGF)-Beta, nerve growth factor (NGF) and platelet-derived growth factor (PDGF)-Beta. All of them contain cystine knot motif and have been implicated in the development of a variety of tumors. hCG stimulates cell growth and differentiation and, therefore, it is highly likely that its function is regulated by the three member MAK kinase cascade, mitogen-activated protein kinase-kinase-kinase (MAPKKK)--MAPKK-extracellular signal-regulated kinase (ERK). The objectives of the proposed studies are to investigate the involvement of the MAP kinase pathway in the cell growth and differentiation by hCG. Pathway-specific DNA microarray technology will be employed to compare the gene expression profiles of hCG and epidermal growth factor (EGF) signaling when they interact with their respective receptors in signaling in a rat SIGC-hCG/; lutropin receptor (LHR) and SIGC-epidermal growth factor receptor (EGFR). This should give us some information on the expression of genes that are common to both signaling pathways. The signaling proteins downstream of ERK and upstream of MAPKKK will be investigated. Lastly, search for a scaffold protein on which these kinases might be organized will be made. The studies will be carried out with the rat SIGC. SIGC has an epithelial morphology and grows in culture without luteinization. Specific short-term goals of the initial studies will include: 1) Transfection of rat SIG cells with hCG/LH and EGF receptor cDNAs separately and selection of stable transfectants, SIGC-hCG/LHR and SIGC-EGFR; 2) Preliminary characterization of SIGC-hCG/LHR and SIGC-EGFR, which will involve a) determination of the presence and concentration of hCG/LH and EGF receptors by binding assays using 125IhCG and 125IEGF and b) study of the effect of hCG on the activation of adenylyl cyclase and phospholipase C and of EGF on the activation of receptor tyrosine kinase; 3) Study the effect of hCG and EGF on the activities of Raf, MEK and ERK; 4) Comparison of the gene expression profiles of signaling by hCG and EGF in SIGC-hCG/LHR and SIGC-EGFR by DNA microarrays; 5) Determination of the downstream and upstream signaling proteins of ERK and Raf kinases respectively by association or immunoprecipitation techniques using specific polyclonaI antibodies; and 6) Search for a scaffold protein for MAP kinase module will be made.
Funding Period: 2002-08-01 - 2005-07-31
more information: NIH RePORT