Change in subcellular localization of overexpressed vaccine peptide in rice endosperm cell that is caused by suppression of endogenous seed storage proteins

摘要

Rice-based peptide vaccine based on T cell epitopes acts as an ideal oral tolerogen for the treatment of type 1 allergic diseases. To improve production yields of oral tolerogen against Japanese cedar pollen allergy, hybrid peptide comprising seven predominant human T cell epitopes (7Crp) derived from Japanese cedar pollen allergens, Cry j 1 and Cry j 2, was produced in transgenic rice seed by expression of its codon optimized gene under the control of the endosperm-specific 26 kD globulin (Glb-1) promoter containing its signal peptide and the simultaneous suppression of endogenous seed storage proteins (SSPs) by RNA interference. Accumulation level of 7Crp peptide produced as a secretory protein was remarkably enhanced by suppression of both the 13-14 kDa prolamins and GluA and GluB glutelins as compared to those under suppression of either of them or in wild type rice. When these SSPs were down-regulated, the 7Crp peptide was observed to be localized in ER lumen as well as ER derived PBs (PB-Is). Especially, accumulation as self-aggregates in ER lumen increased by reduction of the endogenous 13-14 kDa prolamins. It is interesting to note that the absence of C terminal KDEL ER retention signal from the 7Crp peptide resulted in higher level accumulation (116 A mu g/grain) than that containing the KDEL.