The first molluscan TCTP in Venerupis philippinarum: molecular cloning and expression analysis

Translationally controlled tumor protein (TCTP) is one of the abundant and ubiquitously expressed proteins in metazoans. In the present study, the first molluscan TCTP (denoted as VpTCTP) was identified from Venerupis philippinarum haemocytes by EST and RACE approaches. The full-length cDNA of VpTCTP consisted of 1148 nucleotides with an open-reading frame of 555 bp encoding 184 amino acids. The deduced amino acid sequence of VpTCTP shared high similarity with TCTPs from other species, indicating that VpTCTP should be a new member of TCTP family. Several highly conserved motifs, including 5'terminal ologopyrimidine (5'TOP) starting sequence and rich AU and AUUT elements in 3'UTR, were also identified in VpTCTP. The tissue and temporal expression of VpTCTP after Vibrio anguillarum challenge was recorded by quantitative real-time RT-PCR. VpTCTP transcript could be detected in all examined tissues with the highest expression level in haemocytes and the lowest in hepatopancreas. Concerning the time-course expression in haemocytes, the relative expression of VpTCTP mRNA was down-regulated sharply from 6 h to 12 h post-infection. Then, the expression level was obviously up-regulated and reached 3.4-fold to that in the control group at 48 h post challenge. As time progressed, the expression of VpTCTP recovered to the original level at 96 h. All these results indicated that VpTCTP was an acute-phase protein involved in the immune response of V. philippinarum.