Molecular and functional characterization of asprosin receptor, protein tyrosine phosphatase receptor delta (ptprd) in gonads of Channa punctata.

In non-mammalian vertebrates, asprosin was reported for first time in teleost Channa punctata in 2023. The hormone is conspicuously expressed in gonads and exhibits reproductive-phase related differential expression. Recombinant asprosin modulated reproductive functions of C. punctata. However, receptor for asprosin in teleosts remains obscure. Interestingly, we observed a prominent expression of one of the asprosin receptor, protein tyrosine phosphatase receptor delta (ptprd) in gonads of C. punctata. Reproductive phase-dependent expression of ptprd in the gonads showed highest expression during resting and post-spawning phase. We have further studied the in vitro experiment effect of recombinant ss asprosin on ptprd expression in gonads. The ptprd in spotted snakehead (ss) Channa punctata was characterized in silico. In C. punctata ptprd has 1916 residues and was found to be thermostable and hydrophilic. Ptprd had three distinct domains, N-terminal extracellular region with immunoglobulin-like domain (ligand-binding domain) and fibronectin domain, single transmembrane region, and intracellular region with catalytic domain. The 3D model of the immunoglobulin-like domain was constructed for studies on asprosin-ptprd interaction by docking, MD simulation and binding free energy calculations. Thus, the study for the first time suggests ptprd as a probable receptor for asprosin in teleostean species C. punctata.