ATP1A3 encodes the α3 isoform of Na,K-ATPase. In the brain, it is expressed only in neurons. Human ATP1A3 mutations produce a wide spectrum of phenotypes, but particular syndromes are associated with unique substitutions. For arginine 756, at the junction of membrane and cytoplasmic domains, mutations produce encephalopathy during febrile infections. Here we tested the pathogenicity of p.Arg756His (R756H) in isogenic mammalian cells. R756H protein had sufficient transport activity to support cells when endogenous ATP1A1 was inhibited. It had half the turnover rate of wildtype, reduced affinity for Na⁺, and increased affinity for K⁺. There was modest endoplasmic reticulum retention during biosynthesis at 37 °C but little benefit from the folding drug phenylbutyrate (4-PBA), suggesting a tolerated level of misfolding. When cells were incubated at just 39 °C, however, α3 protein level dropped without loss of β subunit, paralleled by an increase of endogenous α1. Elevated temperature resulted in internalization of α3 from the surface along with some β subunit, accompanied by cytoplasmic redistribution of a marker of lysosomes and endosomes, lysosomal-associated membrane protein 1. After return to 37 °C, α3 protein levels recovered with cycloheximide-sensitive new protein synthesis. Heating in vitro showed activity loss at a rate 20- to 30-fold faster than wildtype, indicating a temperature-dependent destabilization of protein structure. Arg756 appears to confer thermal resistance as an anchor, forming hydrogen bonds among four linearly distant parts of the Na,K-ATPase structure. Taken together, our observations are consistent with fever-induced symptoms in patients.

Human Bfl‐1 is an anti‐apoptotic Bcl‐2 family member. Here, we found that Bfl‐1 was converted into a potent death‐promoting protein by green fluorescent protein (GFP) fusion with its N‐terminus. The transient expression of GFP‐Bfl‐1 induced cytochrome c release and triggered apoptosis in 293T cells, which depended on the mitochondrial localization of GFP‐Bfl‐1. Apoptosis induced by GFP‐Bfl‐1 was significantly blocked by the pan‐caspase inhibitor carbobenzoxy‐Val‐Ala‐Asp‐fluoromethyl ketone, but was not blocked by either Bcl‐xL or Bfl‐1. Our findings provide a useful model for understanding the structural basis of Bcl‐2 family proteins that act in an opposite way despite sharing structural similarity between anti‐apoptotic and pro‐apoptotic proteins.

TRIC-A is an intracellular cation channel enriched in excitable tissues that is recently identified as a key modulator of sarcoplasmic reticulum (SR) Ca²⁺ homeostasis through direct interaction with type 2 ryanodine receptors (RyR₂). Given the intimate anatomical and functional coupling between the SR and mitochondria, we investigated whether TRIC-A contributes to SR–mitochondrial crosstalk under cardiac stress conditions. Using a transverse aortic constriction (TAC) model, we found that TRIC-A^−/− mice developed more severe cardiac hypertrophy, underwent maladaptive remodeling, and activated apoptotic pathways compared with wild-type littermates. At the cellular level, TRIC-A-deficient cardiomyocytes were more susceptible to H₂O₂-induced mitochondrial injury and displayed abnormal mitochondrial morphology. Live-cell imaging revealed exaggerated mitochondrial Ca²⁺ uptake during caffeine stimulation and increased propensity for store-overload-induced Ca²⁺ release (SOICR). Complementary studies in HEK293 cells expressing RyR₂ demonstrated that exogenous TRIC-A expression attenuates RyR₂-mediated mitochondrial Ca²⁺ overload, preserves respiratory function, and suppresses superoxide generation. Together, these findings identify TRIC-A as a critical regulator of SR–mitochondrial Ca²⁺ signaling. By constraining mitochondrial Ca²⁺ influx and limiting oxidative stress, TRIC-A safeguards cardiomyocytes against SOICR-driven injury and confers protection against pressure overload-induced cardiac dysfunction.

Mitsugumin 53 (MG53, also TRIM72) is a muscle-enriched tripartite motif protein with a well-established role in acute membrane repair and cytoprotection in striated muscle and other stressed tissues. MG53 is a core component of cellular repair machinery, rapidly sensing membrane disruption and coordinating membrane resealing, mitochondrial preservation, and anti-inflammatory modulation. In contrast to its high expression in skeletal muscle, endogenous MG53 expression in the adult human heart is minimal, raising the question of how MG53 exerts cardioprotective effects in the human heart. Recent studies help address this by identifying MG53 as a circulating regenerative myokine. MG53 is secreted from skeletal muscle into the bloodstream and can reach distal organs, including the heart. These findings support a muscle-to-heart endocrine model in which MG53 mediates tissue crosstalk and helps provide repair capacity to the myocardium when intrinsic cardiac MG53 is low. Here, we summarize recent advances in MG53 biology, emphasizing molecular mechanisms and inter-organ communication underlying cardioprotection. We further highlight translational strategies leveraging recombinant MG53- and MG53-based therapeutics and discuss challenges that must be addressed for future clinical applications. Collectively, these insights support MG53 as an endocrine repair factor linking skeletal muscle to cardiac repair and a potential regenerative cardiovascular target.