Abstract
Calnexin (CNX) is one of the major calcium-binding proteins in endoplasmic reticulum (ER) and plays a crucial role in regulating Ca(2+) homeostasis and unfolded protein response (UPR). In the present study, PyCNX was identified in Yesso Scallop Patinopecten yessoensis. The open reading frame (ORF) of PyCNX was of 1794 bp encoding a putative polypeptide of 598 amino acid residues with an N-terminal signal peptide, a typical calreticulin (CRT) domain and a C-terminal transmembrane domain. The deduced amino acid sequence of PyCNX shared 47.91%-70.16% identities with CNXs from other species. The mRNA transcripts of PyCNX were constitutively expressed in all the examined tissues, including gills, gonad, hepatopancreas, mantle and haemocytes, with the highest expression level in gills. The mRNA transcripts of PyCNX in gills were significantly up-regulated at 1 h (p < 0.01), down-regulated to similar level of Blank group at 3 h (p > 0.05) and 6 h (p > 0.05), and decreased significantly from 12 to 48 h (p < 0.05) after acute high temperature stress (25 °C). PyCNX was mainly located in the ER of haemocytes. The expression profiles of PyATF6, PyIRE1 and PyGRP78 in the gills of scallops after acute high temperature stress were investigated using quantitative real-time PCR. The mRNA transcripts of PyATF6 increased significantly at 1 h, 3 h and 6 h after acute high temperature stress (p < 0.01), then down-regulated to similar level of Blank group at 12 h (p > 0.05) and 24 h (p > 0.05), and finally significantly up-regulated again at 48 h (p < 0.05). Similar to PyATF6, the mRNA transcripts of PyIRE1 were significantly up-regulated at 1 h (p < 0.05), 3 h (p < 0.01), 6 h (p < 0.05) and 48 h (p < 0.05) after acute high temperature stress. The mRNA transcripts of PyGRP78 were significantly up-regulated at 3 h (p < 0.05), reached the highest level at 6 h (p < 0.01) after acute high temperature stress, and kept significant higher level at 12-48 h (p < 0.05). These results indicated that PyCNX was involved in the response upon the acute high temperature stress of scallops probably by regulating UPR.