Ultrastructural variation and key ER chaperones response induced by heat stress in intestinal cells of sea cucumber Apostichopus japonicus

Abstract

The unfolded protein response (UPR) is an important protective and compensatory strategy used during endoplasmic reticulum stress caused by factors including glucose starvation, low pH, or heat shock. However, there is very little information on the possible role(s) of the UPR under adverse conditions experienced by marine invertebrates. We observed that rough endoplasmic reticulum (ER) was dramatically expanded and numerous autophagosomes were accumulated in the intestinal cells of sea cucumbers, Apostichopus japonicus, under heat stress (4 h at 25°C compared with 15°C controls). Moreover, heat stress led to sharp increases in the relative transcript and protein expression levels of two primary ER chaperones: the endoplasmic reticulum resident protein 29-like (ERP29) and protein disulfide-isomerase A6-like (PDIA6). These results suggest a potential adaptive mechanism to deal with heat-induced stress in sea cucumber intestine.