GADD45A is a mediator of mitochondrial loss, atrophy, and weakness in skeletal muscle
George R. Marcotte, Matthew J. Miller, Hawley E. Kunz, Zachary C. Ryan, Matthew D. Strub, Patrick M. Vanderboom, Carrie J. Heppelmann, Sarah Chau, Zachary D. Von Ruff, Sean P. Kilroe, Andrew T. McKeen, Jason M. Dierdorff, Jennifer I. Stern, Karl A. Nath, Chad E. Grueter, Vitor A. Lira, Andrew R. Judge, Blake B. Rasmussen, K. Sreekumaran Nair, Ian R. Lanza, Scott M. Ebert, Christopher M. Adams
George R. Marcotte, Matthew J. Miller, Hawley E. Kunz, Zachary C. Ryan, Matthew D. Strub, Patrick M. Vanderboom, Carrie J. Heppelmann, Sarah Chau, Zachary D. Von Ruff, Sean P. Kilroe, Andrew T. McKeen, Jason M. Dierdorff, Jennifer I. Stern, Karl A. Nath, Chad E. Grueter, Vitor A. Lira, Andrew R. Judge, Blake B. Rasmussen, K. Sreekumaran Nair, Ian R. Lanza, Scott M. Ebert, Christopher M. Adams
View: Text | PDF
Research Article Metabolism Muscle biology

GADD45A is a mediator of mitochondrial loss, atrophy, and weakness in skeletal muscle

Abstract

Aging and many illnesses and injuries impair skeletal muscle mass and function, but the molecular mechanisms are not well understood. To better understand the mechanisms, we generated and studied transgenic mice with skeletal muscle–specific expression of growth arrest and DNA damage inducible α (GADD45A), a signaling protein whose expression in skeletal muscle rises during aging and a wide range of illnesses and injuries. We found that GADD45A induced several cellular changes that are characteristic of skeletal muscle atrophy, including a reduction in skeletal muscle mitochondria and oxidative capacity, selective atrophy of glycolytic muscle fibers, and paradoxical expression of oxidative myosin heavy chains despite mitochondrial loss. These cellular changes were at least partly mediated by MAP kinase kinase kinase 4, a protein kinase that is directly activated by GADD45A. By inducing these changes, GADD45A decreased the mass of muscles that are enriched in glycolytic fibers, and it impaired strength, specific force, and endurance exercise capacity. Furthermore, as predicted by data from mouse models, we found that GADD45A expression in skeletal muscle was associated with muscle weakness in humans. Collectively, these findings identify GADD45A as a mediator of mitochondrial loss, atrophy, and weakness in mouse skeletal muscle and a potential target for muscle weakness in humans.

Authors

George R. Marcotte, Matthew J. Miller, Hawley E. Kunz, Zachary C. Ryan, Matthew D. Strub, Patrick M. Vanderboom, Carrie J. Heppelmann, Sarah Chau, Zachary D. Von Ruff, Sean P. Kilroe, Andrew T. McKeen, Jason M. Dierdorff, Jennifer I. Stern, Karl A. Nath, Chad E. Grueter, Vitor A. Lira, Andrew R. Judge, Blake B. Rasmussen, K. Sreekumaran Nair, Ian R. Lanza, Scott M. Ebert, Christopher M. Adams

×

Figure 8

A constitutively active MEKK4 construct (MEKK4ΔN) decreases MyHC-2B, increases MyHC-2A, and decreases mitochondrial proteins in skeletal muscle.

Options: View larger image (or click on image) Download as PowerPoint
A constitutively active MEKK4 construct (MEKK4ΔN) decreases MyHC-2B, inc...
TA muscles of 8-week-old male C57BL/6 mice were transfected with plasmid DNA. One TA per mouse was transfected with 7.5 mg empty plasmid (control), and the contralateral TA in each mouse was transfected with 7.5 mg plasmid encoding MEKK4ΔN. Seven days posttransfection, bilateral TAs were harvested, and TA protein was subjected to TMT-mass spectrometry, followed by quantification of the relative abundance of 6,870 proteins. Data are from 4 muscles per genotype. (A) Quantification of MEKK4 (MAP3K4) protein. Each data point represents the value from 1 muscle, and bars indicate mean values. Detailed proteomic data are shown in Supplemental Table 5. (B) Fractional abundance of MyHC-2B, MyHC-2X, MyHC-2A, and MyHC-slow, calculated from data in Supplemental Table 6. Each data point represents the value from 1 muscle, and bars indicate mean values. q values were determined with multiple unpaired 2-tailed t tests. (C) Enrichment plots of Reactome pathways that were strongly repressed by MEKK4ΔN, based on GSEA of the proteomic data. All 5 pathways were downregulated with FDR < 10–5. Complete GSEA results are shown in Supplemental Table 7. (D) Schematic illustrating detected proteins involved in the TCA cycle and effect of MEKK4ΔN on levels of those proteins. MEKK4ΔN significantly decreased all the detected proteins (FDR < 0.05). (E) Schematic of mitochondrial electron transport chain complexes I, II, III, and IV, with an underlying heatmap showing detected proteins in those complexes, and the effect of MEKK4ΔN on levels of those proteins. Asterisks indicate FDR < 0.05.