Actin-myosin complex dissociation initiates programmed cell death during cold storage of grass carp muscle

Cytoskeletal integrity is a critical determinant of postmortem cellular stability in muscle tissues, yet its regulatory role in initiating cell death remains poorly defined. In this study, we applied integrated 4D proteomics, immunofluorescence, and Western blotting to investigate cytoskeletal disassembly and programmed cell death pathways in refrigerated grass carp (Ctenopharyngodon idellus) muscle. Results showed that actin-myosin complex dissociation and the upregulation of remodeling proteins (CFL2, TWF2, ARPC4) occurred prior to the activation of apoptosis-related proteins (CAPN1, UCHL1) and cytochrome c release. Meanwhile, declines in SERCA2 and FTH1 indicated calcium and iron homeostasis disturbances, implicating both apoptosis and ferroptosis. Immunofluorescence analysis confirmed the spatial uncoupling of MYH2 and α-actin alongside mitochondrial disruption. These findings suggest that cytoskeletal disintegration may serve as an upstream regulatory event that promotes mitochondrial dysfunction and cell death. This study provides novel mechanistic insight into postmortem muscle deterioration and offers a theoretical framework for understanding early structural triggers of quality loss in cold-stored fish.