Chronic inhibition of the mitochondrial ATP synthase in skeletal muscle triggers sarcoplasmic reticulum distress and tubular aggregates

Abstract

Tubular aggregates (TA) are honeycomb-like arrays of sarcoplasmic-reticulum (SR) tubules affecting aged glycolytic fibers of male individuals and inducing severe sarcomere disorganization and muscular pain. TA develop in skeletal muscle from Tubular Aggregate Myopathy (TAM) patients as well as in other disorders including endocrine syndromes, diabetes, and ageing, being their primary cause unknown. Nowadays, there is no cure for TA. Intriguingly, both hypoxia and calcium dyshomeostasis prompt TA formation, pointing to a possible role for mitochondria in their setting. However, a functional link between mitochondrial dysfunctions and TA remains unknown. Herein, we investigate the alteration in muscle-proteome of TAM patients, the molecular mechanism of TA onset and a potential therapy in a preclinical mouse model of the disease. We show that in vivo chronic inhibition of the mitochondrial ATP synthase in muscle causes TA. Upon long-term restrained oxidative phosphorylation (OXPHOS), oxidative soleus experiments a metabolic and structural switch towards glycolytic fibers, increases mitochondrial fission, and activates mitophagy to recycle damaged mitochondria. TA result from the overresponse of the fission controller DRP1, that upregulates the Store-Operate-Calcium-Entry and increases the mitochondria-SR interaction in a futile attempt to buffer calcium overloads upon prolonged OXPHOS inhibition. Accordingly, hypoxic muscles cultured ex vivo show an increase in mitochondria/SR contact sites and autophagic/mitophagic zones, where TA clusters grow around defective mitochondria. Moreover, hypoxia triggered a stronger TA formation upon ATP synthase inhibition, and this effect was reduced by the DRP1 inhibitor mDIVI. Remarkably, the muscle proteome of TAM patients displays similar alterations in mitochondrial dynamics and in ATP synthase contents. In vivo edaravone treatment in mice with restrained OXPHOS restored a healthy phenotype by prompting mitogenesis and mitochondrial fusion. Altogether, our data provide a functional link between the ATP synthase/DRP1 axis and the setting of TA, and repurpose edaravone as a possible treatment for TA-associated disorders.

Antioxidants restore store‐operated Ca2+ entry in patient‐iPSC‐derived myotubes with tubular aggregate myopathy‐associated Ile484ArgfsX21 STIM1 mutation via upregulation of binding immunoglobulin protein

“…Tubular aggregates were first described in patients with periodic hypokalemic paralysis, 45 and later in several pathological conditions such as inflammatory myopathy, malignant hyperthermia, congenital myasthenic syndromes, alcohol myopathy, prolonged anoxia, diabetes, and endocrine disorders 14 . Chronic inhibition of the mitochondrial ATP synthesis also facilitates formation of tubular aggregates 46 . Interestingly, tubular aggregates also develop in type‐IIB fibers of physiologically aging male mice 47–49 .…”

“… 14 Chronic inhibition of the mitochondrial ATP synthesis also facilitates formation of tubular aggregates. 46 Interestingly, tubular aggregates also develop in type‐IIB fibers of physiologically aging male mice. 47 , 48 , 49 Therefore, tubular aggregate formation is not specific to the constitutive activation of Ca 2+ entry caused by gain‐of‐function mutations in the STIM1 or the ORAI1 gene, and it is possible that the chronic disruption of Ca 2+ homeostasis observed in our patient also caused the tubular aggregate formation.…”

An ETFDH-driven metabolon supports OXPHOS efficiency in skeletal muscle by regulating coenzyme Q homeostasis

“…Mouse motor functions were evaluated using (1) a rotarod test and (2) a two-limb hanging test 43 . All tests were performed in a blinded fashion.…”

“…TMT sixplex isobaric mass tagging analysis was carried out in the CBMSO Proteomics Unit (ProteoRed, PRB3-ISCIII and UAM University, Spain) 43 .…”

Polymorphisms of CRELD1 and DNAJC30 and their relationship with chicken carcass traits

“…In addition, DNAJC30 is also the protein chaperone required for the exchange of damaged complex I subunits in mitochondria ( Stenton et al, 2021 ). ATP-synthase and mitochondrial complex I subunits are highly correlated with the metabolism and development of muscle and fat, which suggested that DNAJC30 may play some roles in skeletal muscle and fat metabolism ( Hong et al, 2014 ; Sanchez-Gonzalez et al, 2022 ). However, there are no reports about their function in skeletal muscle development and their relationship with the chicken carcass.…”