The RyR-like-FKBP12-PKA Complex Regulates Intracellular Ca2+, Unfolded Protein Response and Apoptosis in Patinopecten yessoensis Under High-Temperature Stress

Ryanodine receptor-like (RyR-like) is a key endoplasmic reticulum (ER) Ca2+ release channel governing intracellular Ca2+ homeostasis and cellular stress responses in invertebrates. However, its function in bivalves under high-temperature stress remains unclear. In the present study, one RyR-like was identified from Yesso scallop Patinopecten yessoensis (PyRyR-like). Its function in regulating intracellular Ca2+, IRE1α-mediated unfolded protein response (UPR) and apoptosis in the mantle after high-temperature (25 °C) treatment was investigated using molecular cloning, qRT-PCR, Western blot, pull-down assay, cellular calcium imaging, TUNEL and histology assays; High temperature treatment significantly increased intracellular Ca2+ content at 1 and 6 h (p < 0.05), but decreased it at 3, 12 and 24 h (p < 0.05); meanwhile, the cAMP level, PyPKA activity, mRNA expression level of PyRyR-like, and protein expression levels of PyFKBP12 and PyGRP78 were significantly increased at different times. However, high temperature did not affect the expression level of PyNVL and PyXBP1(S). The SPRY and RYR domains of PyRyR-like separately interacted with PyFKBP12 and PyPKA. Moreover, RyR antagonist Dantrolene reversed high-temperature-induced alterations in Ca concentration, PKA activity, and core UPR- and apoptosis-related molecules, and suppressed Caspase-3 activity. These findings suggest that PyRyR-like plays an important role in the high-temperature response of scallops by regulating intracellular Ca2+ homeostasis and mediating UPR activation and apoptosis, providing new insight into the molecular mechanism underlying scallop adaptation to high temperature.