Isolation and Characterization of Heat Shock Protein 90 in Kumgang Fat Minnow <i>Rhynchocypris kumgangensis</i>

Abstract

Heat shock proteins (Hsps) are molecular chaperones that respond to various external and internal cellular stresses. Hsp90 is an abundant cellular heat shock protein. It has two isoforms, Hsp90α and Hsp90β. In fish, expression of the isoforms is augmented by various stress signals, including thermal change, salinity, pH, ammonia, infection, and environmental pollutants. In this study, we isolated both isoforms of Hsp90, designated rkHsp90α and rkHsp90β, from the liver of Kumgang fat minnow, Rhynchocypris kumgangensis, a small freshwater fish that is endemic to Korea. Sequences of the isolated isoforms showed homology with the corresponding isoforms of teleost Hsp90. Both isoforms of rkHsp90 were highly expressed in the liver compared to other tissues, including brain, gastrointestinal tract, gills, and muscle. Water temperature elevation induced increased hepatic and muscular expression of rkHsp90α, but not rkHsp90β. Both isoforms did not respond to lipopolysaccharide challenges. Exposure to environmental pollutants promoted expression of rkHsp90β, but not rkHsp90α. The collective findings support the proposal that rkHsp90α and rkHsp90β act as molecular chaperones that respond to distinct cellular stresses. Both could serve as useful biomarkers for assessing cellular stress in Kumgang fat minnow.