Molecular Characterization of the Insulin-Like Androgenic Gland Hormone in the Swimming Crab, Portunus trituberculatus, and Its Involvement in the Insulin Signaling System
Qinghua Jiang, Hongkun Zheng, Zheng Liang, Yaojing Wang, Mengen Wang, Xi Xie, Dongfa Zhu
Abstract
The insulin-like androgenic gland hormone (IAG) is mainly produced in the androgenic gland (AG) of the male crustaceans, and is a crucial regulator in male sexual differentiation. In the current study, the full-length cDNA of IAG in the swimming crab, Portunus trituberculatus (Pt-IAG), was cloned and characterized. Similar to other reported IAGs, the deduced amino acid sequence of Pt-IAG was consist of signal peptide, B chain, C peptide and A chain, containing 6 conserved cysteines that form two inter-chain disulfide bonds and one intra-B chain disulfide bond. Tissue distribution analysis suggested that the Pt-IAG cDNA was highly expressed in the AG, and was slightly expressed in several other tissues. A short-term silencing of PtIAG with double-stranded RNA was found to reduce the transcript levels of insulin receptor (Pt-IR) and insulin-like growth factor-binding protein (Pt-IGFBP), suggesting the Pt-IAG might perform its biological function through the insulin family-based signaling system. Bilaterally eyestalk ablation induced the expression of Pt-IAG in AG at 4 and 7 d after surgery, while the transcript levels of Pt-IR in AG and testis and Pt-IGFBP in muscle, testis, and thoracalia ganglia were significantly decreased from 1 d after surgery. The results suggested that the Pt-IR and Pt-IGFBP might also be the targets of eyestalk neuropeptides, and responded to the ESA independent of IAG regulation.