Inhibitory Role of the Mud Crab Short Neuropeptide F in Vitellogenesis and Oocyte Maturation via Autocrine/Paracrine Signaling

Abstract

Neuropeptides, in addition to their classical role in the nervous system, act on intraovarian factors to regulate reproductive functions in vertebrates. However, this function of neuropeptides has not been characterized in crustaceans. Short neuropeptide F (sNPF), a highly conserved invertebrate neuropeptide, has been reported to be involved in feeding, metabolism, and in differentiation processes including reproduction. Although sNPF and its receptor (sNPFR) have been detected in the ovary in different species, ovarian colocalization of sNPF/sNPFR has not been investigated. In this study, we identified <i>Scylla paramamosain</i> (mud crab) sNPF (<i>Sp</i>-sNPF) as an endogenous ligand for the <i>S. paramamosain</i> orphan G protein-coupled receptor NPY2R in mammalian cell line HEK293T. We designated this receptor as <i>Sp-sNPFR</i>. RNA <i>in situ</i> hybridization in pre-vitellogenic ovary and reverse transcription-PCR on isolated denuded oocytes and follicle layers showed that <i>Sp-sNPF</i> was exclusively localized to the follicle cells, whereas <i>Sp-sNPFR</i> was detected in both follicle cells and oocytes. We also found that <i>Sp</i>-sNPF partly suppressed spontaneous maturation of denuded oocytes and caused intracellular cAMP accumulation and Ca²⁺ mobilization. Moreover, injection of synthetic <i>Sp</i>-sNPF peptides inhibited the expression of vitellogenin and vitellogenin receptor genes <i>in vivo</i>. These combined results suggest for the first time that <i>Sp</i>-sNPF may have inhibitory functions in vitellogenesis and oocyte maturation possibly via the autocrine/paracrine pathway.