Molecular cloning and characterization of a receptor for activated protein kinase C1 (RACK1) from Chinese white shrimp; Fenneropenaeus chinensis.

Receptor for activated C kinase 1 (RACK1), which has seven tandem WD40 domains, is a scaffolding protein. RACK1 plays different roles by binding to different partner proteins. It is involved in hormone signaling and development, and now some evidence indicates it may have a role in innate immunity. In this paper, RACK1 cDNA from Chinese white shrimp (FcRACK1) was identified. The full length of the FcRACK1 gene is 1037 bp, including a 30 bp 5'UTR, a 957 bp ORF encoding a 318 amino acid protein, and a 50 bp 3'UTR with the polyadenylation sequence AATAAA and a poly (A) tail. The FcRACK1 protein is characterized by seven WD40 repeat domains; the ending two amino acids of each WD40 domain are WK, WD, WN, WS, WD, WD, and WQ, respectively. The length of each domain is between 30 and 44 amino acids. Multiple alignments of RACK1s showed that RACK1s are highly conserved. RT-PCR showed that FcRACK1 could be detected in hemocytes, the heart, hepatopancreas, gills, stomach, intestine, and ovary. FcRACK1 in hemocytes was down-regulated after a 2h WSSV challenge, and FcRACK1 in gills was up-regulated after a 2 h Vibrio challenge. FcRACK1 in ovary went down after a 12 h Vibrio challenge and then up-regulated at 24 h. FcRACK1 in ovary was first down-regulated at 2 h after a WSSV challenge and then up-regulated to the highest level at 6 h. It finally went down from 12 to 24 h. In hepatopancreas, FcRACK1 was also up-regulated by microbe challenge. Our results indicated its probable role in shrimp innate immunity.