Identification of Two Insulin Receptors from the Swimming Crab Portunus trituberculatus: Molecular Characterization, Expression Analysis, and Interactions with Insulin-Like Androgenic Gland Hormone.

AbstractThe insulin-like androgenic gland hormone is a crucial sexual regulator that is involved in the masculine sexual differentiation of crustaceans. As an insulin-like peptide, the insulin-like androgenic gland hormone has been proposed to act through the insulin receptor-mediated pathway. The present study cloned and characterized two insulin receptors (PtIR1 and PtIR2) from the swimming crab Portunus trituberculatus hallmarked with a conserved intracellular tyrosine kinase catalytic domain and several other typical insulin receptor domains in their deduced amino acid sequences. Both insulin receptors were predominately expressed in the testis and the insulin-like androgenic gland hormone-producing organ androgenic gland. Their testicular expression during the annual cycle suggested that they may play critical roles in spermatogenesis. By using the protein colocalization analysis in HEK293 cells, interactions of PtIAG with the two PtIRs were further confirmed. In addition, the insulin receptor antagonist was found to attenuate the stimulatory effects of androgenic gland homogenate on the phosphorylated MAPK levels in testis explants, suggesting that the insulin receptor-dependent MAPK pathway may be essential for insulin-like androgenic gland hormone functions.