Novel member of Ras family proteins from Disk Abalone (Haliotis discus discus): Structural profiling and its transcriptional modulation under host pathologic conditions

Abstract

Among small GTPases, the Ras family proteins capture a remarkable place in dictating cellular proliferation, differentiation and survival in development of an organism. Major members of the Ras family include Ras (H-Ras, K-Ras, N-Ras), Rap1, and Rap2, all of which can act as oncogenes upon mutation. In the present study, a novel Ras family protein (AbRFP) was characterized from Disk Abalone (Haliotis discus discus), an economically important, edible marine gastropod; further analyzing its transcriptional profile in healthy and immune-challenged animals. The full-length cDNA of AbRFP is 2704 bp and it consists of an open reading frame of 552 bp, encoding a 184 amino acid peptide with a calculated molecular mass of ~21 kDa and isoelectric point of 8.63. The amino acid sequence resembles the characteristic features of typical Ras family proteins, including GTP/Mg2+ binding sites and guanine nucleotide exchange factor (GEF) interaction sites, as predicted by the NCBI-conserved domain database server. Phylogenetic study of AbRFP showed the generally accepted relationships, with AbRFP exhibiting highest proximity to a Ras protein from Portuguese oyster. Quantitative realtime PCR detected ubiquitous AbRFP mRNA expression, with strongest levels in muscle along with mantle and the lowest level in hepatopancreas. The AbRFP transcriptional profile in gills of Abalone challenged with Vibrio parahaemolyticus or viral hemorrhagic septicemia virus (VHSV) demonstrated significant up-regulations (p < 0.05) at 12 h and 24 h post-injection (p.i.), respectively. Moreover, significant elevation (p < 0.05) of mRNA expression was detected in hemocytes at 72 h p.i. with V. parahaemolyticus. These findings suggest that AbRFP may play a role under pathological conditions in Disk Abalone.