| In our research,we are interested in the characterization of FAK(focal adhesion kinase) and Arf(ADP ribosylation factor),and we also established an efficient method of phage display screening to seek for their possible binding candidates,which will pave the way to study the signaling mechnism of MjFAK and its downstream small G proteins in the WSSV infection.Focal adhesion kinase(FAK),a member of non-receptor tyrosine kinase,is extensively addressed as pivotal roles in cell adhesion,anti-apoptosis,actin assembly, tumor formation and progression.Here MjFAK was characterized as the first FAK family protein-tyrosine kinase in crustaceans.Sequence analysis displayed that MjFAK shared strong similarity to FAK family protein-tyrosine kinase,including conserved tyrosine phosphorylation sites,PTK domain and FAT domain.Tyr397 and Tyr577 were found to be phosphorylated in vivo.Moreover,pMjFAK including MjFAK(pY397) and MjFAK(pY577) increased at the early infection stage, accompanied by an increase of hemocyte adhesion activity of fibronectin.These results suggest that pMjFAK may not only promote the WSSV infection,but also participate in the defense mechanism via the enhancement of the immune-cell adhesion.Arfs belong to the small G protein family.Here a member of Classâ…¡Arfs was cloned from M.japonicus(designated as MjArf4).MjArf4 was initially found to be upregulated significantly post infection,which indicated that MjArf4 have a connection with WSSV infection.The promoter of MjArf4 was analyzed and a conserved element CRE was found 18 bp upstream from transcription site.Promoter activity assay showed that CRE may have an inhibited effect on MjArf4 transcription. In High Five cells,MjArf4 was localized at Golgi and such distribution was dependant on GTP with site mutation analysis.Moreover,BFA have no effect on hemocyte phagocytosis of WSSV.Overall,these data provide evidence that shrimp Arf may have an important role in the late phase of WSSV infection.
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