Dimerizations of the wallaby gonadotropin-releasing hormone receptor and its splice variants

Dimerization between wallaby GnRH-R and its splice variants was examined. A baculovirus-based fluorescence resonance energy transfer (Bv-FRET) assay was used to assess protein-protein interaction between wild type wallaby GnRH-R and splice variants (GnRH-RΔ1 and GnRH-RΔ2). FRET analysis demonstrated that GnRH-R, GnRH-RΔ1 or GnRH-RΔ2 are capable of assembling as homodimers. When GnRH-R is co-expressed with GnRH-RΔ1 or GnRH-RΔ2 splice variants, GnRH-R can form heterodimers with GnRH-RΔ1 and GnRH-RΔ2. GnRH agonist is not required for the initiation of dimerization. However, the addition of a GnRH agonist enhances the FRET signal in the GnRH-R homodimers, indicating that the GnRH agonist may be involved in modulating the extent of dimerization. In addition, this study reveals that dimerization of GnRH-R may be mediated by two or more protein interaction domains. One of them is probably located between amino acid residues 74 and 174, and the other one between residues 175 and 328. This is the first study to show dimerization between a wild type mammalian GnRH-R and its splice variants. It provides additional support for the potential involvement of splice variants in GnRH-R signaling.