The role of reduced phosphorylation in desmin stability: A pathway to enhanced ubiquitination and degradation

Desmin degradation is pivotal for myofibrillar integrity and meat tenderization, yet how phosphorylation status relates to desmin ubiquitination and proteolysis remains poorly understood. An in vitro incubation model of bovine longissimus thoracis lumborum homogenates with manipulated phosphorylation levels was established using phosphatase inhibitor (PI) or activator (PA). The samples in the PA group showed increased desmin ubiquitination and accelerated the decline in desmin abundance compared with those in the PI group (P < 0.05). Under reduced total phosphorylation, the calpain activity in the PA group was lower whereas 20S proteasome activity was higher between 4 h and 72 h (P < 0.05). Molecular dynamics simulations suggested that phosphorylation and deubiquitination stabilize desmin by favoring a more compact conformation. Collectively, the reduced total phosphorylation was associated with enhanced desmin ubiquitination and proteasome-associated degradation, providing new insight into the regulation of cytoskeletal protein degradation during postmortem and its potential relevance to meat quality development.