Differential gene expression of HSC70/HSP70 in yellowtail cells in response to chaperone-mediated autophagy.

A cell line derived from the tailfin of the marine teleost yellowtail fish Seriola quinqueradiata was established to examine cellular temperature regulation in an ectothermic animal. Three cytosolic members of the HSP70 family, heat-shock cognate proteins HSC70-1, HSC70-2 and heat-shock protein HSP70, were isolated from cultured yellowtail cells as stress-responsive biomarkers. Expression of hsp70 was heat-inducible, in contrast to the hsc70-1 gene product, which was expressed constitutively. In addition, expression of hsc70-2 was only induced under severe heat-shock conditions. Subcellular fractionation and immunocytochemistry showed localization of HSC70/HSP70 in the lysosomes, indicating that chaperone-mediated autophagy is induced by heat shock. Thus, chaperone-mediated autophagy is assisted by HSC70/HSP70, and heat-inducible expression of the genes encoding these proteins may be responsible for survival and adaptation under heat-shock conditions in fish cells.