Synaptotagmin-7 drives stress-induced cardiomyocyte necroptosis via the p53-Bak-mPTP axis.

Rationale: High-intensity psychological and physiological stress contributed greatly to development of cardiac disorders in contemporary society. However, the underlying molecular mechanisms remain largely unknown. Synaptotagmin-7 (Syt7), a Ca²⁺ sensor with high affinity, has been associated with synaptic transmission and tumor progression, but its role in cardiac stress responses remains poorly defined. Methods: Corticosterone (CORT) was used to induce stress injury in vivo and in vitro. The expression of Syt7 was modulated by genetic knockout, injection of adenoviral siRNA or injection of adeno-associated virus serotype 9 (AAV9) shRNA. Cardiac function and remodeling were evaluated by echocardiography, electrocardiography, and histological staining. Necroptosis was analyzed by propidium iodide (PI) staining, lactate dehydrogenase (LDH) release detection, and necroptosis marker levels. Ca²⁺ overload, ROS production, mitochondrial permeability transition pore (mPTP) opening, and bioenergetic profiling were assessed to evaluate mitochondrial function. Co-IP assay was performed to detect protein interaction, and ChIP- qPCR was performed to assess transcriptional regulation. Results: Syt7 expression was significantly upregulated in both cardiomyocytes and heart tissues exposed to CORT. Both genetic knockout and cardiomyocyte-specific knockdown of Syt7 significantly preserved cardiac function and rhythm, and alleviated myocardial hypertrophy and fibrosis in CORT-treated mice. Mechanistically, Syt7 regulated necroptosis by promoting calcium overload, ROS production, mitochondrial ΔΨm dissipation, and mPTP prolonged opening. Notably, Syt7 interacted with transcription factor p53 and enhanced p53- mediated transcription of Bcl-2 homologous antagonist/killer (Bak). Syt7, p53 and Bak constitute a novel signaling axis to regulate mitochondrial dysfunction and necroptosis. Therapeutically, cardiac delivery of Syt7-targeting siRNA via adenoviral vectors significantly alleviated structural remodeling, electrophysiological instability, and myocardial necrosis in CORT-challenged mice. Conclusions: The study identified Syt7 as a novel upstream regulator involved in cardiomyocyte necroptosis triggered by stress stimuli through a p53-Bak-mPTP pathway. Therapeutic targeting of Syt7 offers a promising strategy for protecting the heart against psychological or neuroendocrine stress-related injury.