Identification, characterization, and function of GRP94 and HSP90β in cold stress response in cold water fish Phoxinus lagowskii

The glucose-regulated protein (GRP94) and HSP90β are highly conserved and diverse molecular chaperones that could prevent protein aggregation and denaturation while also playing an important role in cellular stress responses. We show through our study the cloning and characterization of GRP94 and HSP90β genes and analyze their mRNA expression in the brain, heart, liver, and muscle tissues of Phoxinus lagowskii after exposure to cold stress. The strong stress resistance to the temperature of this cold-water fish in high latitudes makes it a good model for this study. GRP94 and HSP90β contain a KDEL and a MEEVD motif at the C-terminus and a histidine kinase-like ATPases (HATPases-c domain) at the N-terminus. These genes were found to be highly expressed in the liver, gills, ovary, testis, and other tissues. In the brain, liver, and muscle tissue, there was an increase in GRP94 mRNA expression during early acute cold stress compared to a control fish. However, the mRNA expression levels of HSP90β increase in the brain and heart in response to exposure to acute cold stress. Relative long-term stress showed no significant difference in the GRP94 and HSP90β expression levels in the liver, heart, and muscle tissue. Significantly high expression of GRP94 was shown in the brain during 14 days, suggesting that these two genes may protect brain tissue from damage during relative long-term cold stress. Our work suggests that HSP90 enhances AKT signaling and may participate in the glucose mechanism. Furthermore, HSP90 may activate IKK signaling via AKT, resulting in a variety of immune responses. This concludes the first study to focus on the GRP94 and HSP90β functions in P. lagowskii during cold stress and provides important tools for future research into HSP90 and GRP94 genes in cold-water fish