FIGURE 7. Role of caspases in TWEAK-induced activation of NF-κB and MuRF1 expression.

A). C2C12 myotubes were incubated with 10 µM of Z-FA-FMK, Z-VAD-FMK or Ac-DMQD-CHO peptide for 3h followed by addition of 100 ng/ml TWEAK for 1h and measurement of NF-κB DNA-binding activity by EMSA. Representative EMSA gel presented here from three independent experiments presented here demonstrates that treatment with Z-VAD-FMK partially inhibits the TWEAK-induced activation of NF-κB in myotubes. B). C2C12 myotubes were incubated with 10 µM of Z-FA-FMK, Z-VAD-FMK or Ac-DMQD-CHO peptide for 3h followed by treatment with TWEAK (100 ng/ml) for 6h and measurement of MuRF1 mRNA levels by QRT-PCR. Data presented here show that Z-VAD-FMK significantly inhibits the TWEAK-induced expression of MuRF1 in myotubes. *p<0.05, values significantly different from TWEAK-treated myotubes incubated with Z-FA-FMK. C). Representative immunoblots presented here demonstrate that Z-VAD-FMK reduces the protein levels of MuRF1 in C2C12 myotubes in response to TWEAK. The levels of tubulin were not affected by either of these treatments. D). C2C12 myotubes were incubated with 10 µM of Z-FA-FMK, Z-VAD-FMK, or Ac-DMQD-CHO peptide for 3h, treated with TWEAK (100 ng/ml) for 6h, and mRNA levels of Beclin1 were measured by QRT-PCR. Data from three independent experiments presented here show that neither Z-VAD-FMK nor Ac-DMQD-CHO had any significantly effect on TWEAK-induced expression of Beclin1 in myotubes.