Six-week-old Tak1^fl/fl and Tak1^mKO mice were given i.p. injections of tamoxifen, and 3 weeks later, skeletal muscle were collected and processed for biochemical analysis. (A) Immunoblots demonstrating the protein levels of MyHC fast-type, tropomyosin, troponin, sarcomeric α-actin, dystrophin, and unrelated protein GAPDH in GA muscle of Tak1^fl/fl and Tak1^mKO mice. Dystrophin was run on a separate gel with loading control GAPDH. (B) Densitometry quantification of relative protein levels of MyHC fast-type, tropomyosin, troponin, sarcomeric α-actin, and dystrophin in GA muscle of Tak1^fl/fl and Tak1^mKO mice. (C) Relative mRNA levels of Myh4 in GA muscle of Tak1^fl/fl and Tak1^mKO mice assayed by qPCR. (D) Tak1^fl/fl and Tak1^mKO mice were given i.p. injections of puromycin (0.04 μmol/g body weight). The mice were euthanized 30 minutes later, and GA muscle was collected and processed by Western blot. Immunoblots of puromycin-tagged protein and unrelated protein GAPDH in GA muscle of Tak1^fl/fl and Tak1^mKO mice. (E) Densitometry quantification of relative levels of puromycin-tagged proteins in GA muscle of Tak1^fl/fl and Tak1^mKO mice. (F) Fold change in 20S proteasome activity in GA muscle of Tak1^fl/fl and Tak1^mKO mice measured using a commercially available kit (Catalog # K245, BioVision). (G) Immunoblots showing relative amounts of ubiquitin-conjugated protein and unrelated protein GAPDH in skeletal muscle of Tak1^fl/fl and Tak1^mKO mice. (H) Densitometry quantification of relative levels of ubiquitin-conjugated proteins. (I) Relative mRNA levels of MAFbx/Atrogin-1, MuRF1, Nedd4, and MUSA1 in skeletal muscle of Tak1^fl/fl and Tak1^mKO mice. (J) Relative mRNA levels of autophagy related genes LC3B, Beclin-1, Atg5, Gabarapl1, and Atg12 in skeletal muscle of Tak1^fl/fl and Tak1^mKO mice. (K) Representative immunoblots of LC3B-I/II and unrelated protein GAPDH in skeletal muscle of Tak1^fl/fl and Tak1^mKO mice. (L) Densitometry quantification of the ratio of LC3B-II vs. LC3B-I in skeletal muscle of Tak1^fl/fl and Tak1^mKO mice. n = 4 or 5 in each group. Error bars represent ± SEM. *P < 0.05 values significantly different from corresponding Tak1^fl/fl mice by unpaired 2-tailed t test.