The expression profile of a multi-stress inducible transient receptor potential vanilloid 4 (TRPV4) in Pacific oyster .

Transient receptor potential vanilloid 4 (TRPV4) is one of the major non-selective cation channel proteins, which plays a crucial role in sensing biotic and abiotic stresses, such as pathogen infection, temperature, mechanical pressure and osmotic pressure changes by regulating Ca homeostasis. In the present study, a TRPV4 homologue was identified in Pacific oyster , designated as TRPV4. The open reading frame (ORF) of TRPV4 was of 2298 bp encoding a putative polypeptide of 765 amino acid residues with three typical ankyrin domains and six conserved transmembrane domains of TRPV4 subfamily proteins, as well as multiple N-glycosylation sites, cAMP- and cGMP-dependent protein kinase phosphorylation sites, protein kinase C phosphorylation sites, casein kinase II phosphorylation sites, and prokaryotic membrane lipoprotein lipid attachment site. The deduced amino acid sequence of TRPV4 shared 20.5%-26.2% similarity with TRPV4s from other species. During the early ontogenesis stages of oyster, the mRNA transcripts of TRPV4 were detectable in all the stages with the highest expression level in fertilized eggs and the lowest in D-hinged larvae. In adult oyster, the TRPV4 mRNA could be detected in all the examined tissues, including gill, hepatopancreas, adductor muscle, labial palp, mantle and haemocyte, with the highest expression level in gill (45.08-fold of that in hepatopancreas, < 0.05). In immunocytochemical assay, the TRPV4 positive signals were distributed in both endoplasmic reticulum and cytoplasmic membrane of oyster haemocytes. The mRNA expression of TRPV4 in gill was significantly up-regulated after high temperature stress at 30°C ( < 0.05) and after stimulation ( < 0.05). These results indicated that TRPV4 was a classical member of TRPV4 family in oyster, which was induced by either biotic or abiotic stimulations and involved in mediating the stress response of oysters.