Loss of membrane integrity drives myofiber death in lipin1‐deficient skeletal muscle

• Published in: Physiological reports 2020-10, Vol.8 (20), p.e14620-n/a
• Main Authors: Ramani Sattiraju, Sandhya, Jama, Abdulrahman, Alshudukhi, Abdullah A., Edward Townsend, Nicholas, Reynold Miranda, Daniel, Reese, Rebecca R, Voss, Andrew A., Ren, Hongmei
• Format: Article
• Language: English
• Subjects: Animals; Antibodies; Apoptosis; BAX protein; Caspase; Cell death; Cell Membrane - metabolism; Cell Membrane Permeability; Creatine; Creatine kinase; Creatine Kinase - metabolism; Gene expression; Immunoglobulin G; Kinases; Laboratories; lipin1; membrane integrity; Mice; Mice, Inbred C57BL; Molecular modelling; Muscle Contraction; Muscle Fibers, Skeletal - metabolism; Muscle Fibers, Skeletal - physiology; Muscular dystrophy; Musculoskeletal system; Necroptosis; necrosis; Original Research; Phosphatase; Phosphatidate Phosphatase - deficiency; Phosphatidate Phosphatase - genetics; Phosphatidate Phosphatase - metabolism; Physiology; Proteins; Rhabdomyolysis; Skeletal muscle
• ISSN: 2051-817X
• DOI: 10.14814/phy2.14620

Mutations in lipin1 are suggested to be a common cause of massive rhabdomyolysis episodes in children; however, the molecular mechanisms involved in the regulation of myofiber death caused by the absence of lipin1 are not fully understood. Loss of membrane integrity is considered as an effective inducer of cell death in muscular dystrophy. In this study, we utilized a mouse line with selective homozygous lipin1 deficiency in the skeletal muscle (Lipin1Myf5cKO) to determine the role of compromised membrane integrity in the myofiber death in lipin1‐deficient muscles. We found that Lipin1Myf5cKO muscles had significantly elevated proapoptotic factors (Bax, Bak, and cleaved caspase‐9) and necroptotic proteins such as RIPK1, RIPK3, and MLKL compared with WT mice. Moreover, Lipin1Myf5cKO muscle had significantly higher membrane disruptions, as evidenced by increased IgG staining and elevated uptake of Evans Blue Dye (EBD) and increased serum creatine kinase activity in Lipin1Myf5cKO muscle fibers. EBD‐positive fibers were strongly colocalized with apoptotic or necroptotic myofibers, suggesting an association between compromised plasma membrane integrity and cell death pathways. We further show that the absence of lipin1 leads to a significant decrease in the absolute and specific muscle force (normalized to muscle mass). Our work indicates that apoptosis and necroptosis are associated with a loss of membrane integrity in Lipin1Myf5cKO muscle and that myofiber death and dysfunction may cause a decrease in contractile force. Our data show that loss of membrane integrity is strongly associated with necroptosis and apoptosis in the lipin1 deficient muscle.