Meeting Abstract

29.10  Jan. 5  Characterization of the Lamprey GnRH Receptor OKAMOTO, Kazu*; FREAMAT, Mihael; SOWER, Stacia; Univ. of New Hampshire ker2@unh.edu

The recently cloned lamprey gonadotropin-releasing hormone (GnRH) receptor was shown to have several unique features, including the longest intracellular C-terminal tail (120 aa) of any previously described GnRH receptor (Silver et al., 2005, Silver and Sower, 2006). Activation of the lamprey GnRH receptor was shown to stimulate cAMP production in a dose dependant manner when treated with either lamprey GnRH-I or lamprey GnRH-III. Truncation analysis indicated that the first 40 amino acids of the lamprey GnRH receptor C-terminal tail contained a motif required for cAMP accumulation. Competitive, intact cell binding assays suggested that the lamprey GnRH receptor was lamprey GnRH-III selective. The lamprey GnRH receptor was also shown to undergo rapid ligand dependant internalization, which was significantly diminished in the tail-less truncated form. In the current study further characterization of the first 40 amino acids of the C-terminal tail was performed in which lamprey GnRH-III was used to stimulate cAMP accumulation. The �HFRK like� motif HVRR occurring in the first 5 amino acids was found to be required for cAMP accumulation by exhibiting a drastic decrease in cAMP accumulation when mutated. Moreover, truncations of 10, 20, and 30 amino acids of the first 40 amino acids of the c-terminal tail yielded a significant decrease in ligand mediated receptor internalization implicating specific residues required for internalization to occur. These data support the significance of the HFRK like motif HVRR in stimulating cAMP. In summary, the study of the GnRH receptor binding from the ancestral lamprey can provide insight into the evolution of the binding properties of the GnRH receptor family. This was supported by NSF 0421923 to SAS.