Characterization of Corticotropin-releasing Hormone Receptors (CRHRs) and Binding Proteins (CRHBPs) in Nile Tilapia: Molecular identification, functional analysis and tissue distribution

Corticotropin-releasing hormone (CRH) mediates various physiological/pathological roles such as stress and reproduction in vertebrates by specifically activating its receptors (CRHRs), and the regulation is intricately intertwined with the CRH binding protein (CRHBP). Although numerous research on mammalian CRHRs and CRHBP has been conducted, reports regarding the teleost CRHRs and CRHBP are limited. Herein, using Nile tilapia (ti-) as a model, we conducted the characterization, functional analysis, and examination of tissue distribution of tiCRHRs and tiCRHBPs. Our study showed that: (1) tiCRHR1a, tiCRHR1b and tiCRHR2 encoded proteins of 432, 436 and 414 amino acids (-aa), while tiCRHBP1 and tiCRHBP2 were predicated to generate a 323- and 322-aa precursor respectively; (2) All tiCRHRs could be activated by tiCRH and subsequently coupled to cAMP/PKA signaling pathways, while only tiCRHR1a and tiCRHR1b could trigger MAPK/ERK signaling cascade; (3) tiCRHBP1 and tiCRHBP2 could does-dependently suppress tiCRH-upregulated luciferase activity in HEK293 cells expressing tiCRHRs; (4) All tiCRHRs mRNA were considerably detected in the central nervous system (CNS), but they exhibited distinct expression pattern in examined peripheral tissues; (5) tiCRHBP1 exhibited an exclusive expression pattern in the pituitary, whereas tiCRHBP2 mRNA was abundantly expressed in the telencephalon. Collectively, our data will help to facilitate a better understanding of the members and functions of CRHRs and CRHBP in teleost.