TAT Improves in vitro Transportation of Fortilin Through Midgut and into Hemocytes of White Shrimp Litopenaeus vannamei

Fortilin is a multifunctional protein implicated in many important cellular processes. Since injection of Pm-fortilin reduces shrimp mortality caused by white spot syndrome virus （WSSV）, there is potential application of fortilin in shrimp culture. In the present study, in order to improve trans-membrane transportation efficiency, the protein transduction domain of the transactivator of transcription （TAT） peptide was fused to fortilin. The Pichia pastoris yeast expression system, which is widely accepted in animal feeds, was used for production of recombinant fusion protein. Green fluorescence protein （GFP） was selected as a reporter because of its intrinsic visible fluorescence. The fortilin, TAT and GFP fusion protein were constructed. Their trans-membrane transportation efficiency and effects on immune response of shrimp were analyzed in vitro. Results showed that TAT peptide improved in vitro uptake of fortilin into the hemocytes and midgut of Litopenaeus vannamei. The phenoloxidase （PO） activity of hemocytes incubated with GFP-Fortilin or GFP-Fortilin-TAT was significantly increased compared with that in the control without expressed fortilin. The PO activity of hemocytes incubated with 200 μg mL-1 GFP-Fortilin-TAT was significantly higher than that in the group with the same concentration of GFP-Fortilin. Hemocytes incubated with GFP-Fortilin-TAT at all concentrations showed significantly higher nitric oxide synthase （NOS） activity than those in the control or in the GFP-Fortilin treatment. The present in vitro study indicated that TAT fusion protein improved the immune effect of fortilin.