FBXO32 and chronic obstructive pulmonary disease: MuRF1 and Atrogin1 are important ubiquitin ligases in the ubiquitin-proteasome pathway that mediate muscle proteolysis, and here, we found that their corresponding gene expressions of MuRF1 and Atrogin1 were significantly upregulated in skeletal muscles of COPD mice (Figure 2F).