Voluntary wheel running mitigates disease in an Orai1 gain-of-function mouse model of tubular aggregate myopathy

Tubular aggregate myopathy (TAM) is an inherited skeletal muscle disease associated with progressive muscle weakness, cramps, and myalgia. Tubular aggregates (TAs) are regular arrays of highly ordered and densely packed SR straight-tubes in muscle biopsies; the extensive presence of TAs represent a key histopathological hallmark of this disease in TAM patients. TAM is caused by gain-of-function mutations in proteins that coordinate store-operated Ca2+ entry (SOCE): STIM1 Ca2+ sensor proteins in the sarcoplasmic reticulum (SR) and Ca2+-permeable ORAI1 channels in the surface membrane. We have previously shown that voluntary wheel running (VWR) prevents formation of TAs in aging mice. Here, we assessed the therapeutic potential of endurance exercise (in the form of VWR) in mitigating the functional and structural alterations in a knock-in mouse model of TAM ( Orai1G100S/+ or GS mice) based on a gain-of-function mutation in the ORAI1 pore. WT and GS mice were singly-housed for six months (from two to eight months of age) with either free-spinning or locked low profile wheels. Six months of VWR exercise significantly increased soleus peak tetanic specific force production, normalized FDB fiber Ca2+ store content, and markedly reduced TAs in EDL muscle from GS mice. Six months of VWR exercise normalized the expression of mitochondrial proteins found to be altered in soleus muscle of sedentary GS mice in conjunction with a signature of increased protein translation and biosynthetic processes. Parallel proteomic analyses of EDL muscles from sedentary WT and GS mice revealed changes in a tight network of pathways involved in formation of supramolecular complexes, which were also normalized following six months of VWR. In summary, sustained voluntary endurance exercise improved slow twitch muscle function, reduced the presence of TAs in fast twitch muscle, and normalized the muscle proteome of GS mice consistent with protective adaptions in proteostasis, mitochondrial structure/function, and formation of supramolecular complexes. ### Competing Interest Statement The authors have declared no competing interest. * ATP : Adenosine triphosphate BTS : N-benzyl-p-toluene sulfonamide CASQ1 : Calsequestrin 1 CSA : Cross-sectional area EDL : Extensor digitorum longus muscle EM : Electron microscopy ER : Endoplasmic reticulum FDB : Flexor digitorum brevis muscle FDR : False discovery rate GAPDH : Glyceraldehyde-3-phosphate dehydrogenase GO : Gene ontology GS : Orai1G100S/+ mouse model HSP70 : Heat shock 70kDa protein IACUC : Institutional Animal Care and Use Committee KEGG: Kyoto Encyclopedia of Genes and Genomes MCU : Mitochondrial Ca2+ uniporter NCX : Na+-Ca2+ exchanger NGS : Normal goat serum PBS : Phosphate-buffered saline PMCA : Plasma membrane Ca2+ ATPase ROS : Reactive oxygen species RT : Room temperature RYR1 : Ryanodine receptor 1 SDS : Sodium dodecyl sulfate SED : Sedentary, Sed (non-exercised) S.E.M. : Standard error of the mean SERCA : Sarco/endoplasmic reticulum Ca2+ ATPase SOCE : Store-operated Ca2+ entry SR : Sarcoplasmic reticulum STIM1 : Stromal interaction molecule 1 TA : Tubular aggregate TAM : Tubular aggregate myopathy TEAB: Triethylammonium bicarbonate TFA : Trifluoroacetic acid TBS : Tris-buffered saline UCAR : University Committee on Animal Resources VDAC : Voltage-dependent anion channel VWR : Voluntary wheel running (exercised) WT : Wild type mouse