Fig. 3. C/EBP Transcription Factors Mimic the Response to Proteasome Stress and Induce Amyrel Expression.

(A) Similar gene expression changes (R²=0.808) are induced by muscle-specific Prosβ1^RNAi and Prosβ5^RNAi. (B) No correlation (R²=0.029) is found when Prosβ1^RNAi and Prosβ5^RNAi are each compared to GFP^RNAi (all normalized to white^RNAi; n = 3).

(C) Similar gene expression changes (R²=0.447; and R²=0.771 for p<0.05) are induced by muscle-specific Prosβ5^RNAi and CG6272^RNAi. (D) No correlation is found when compared control GFP^RNAi (R²=0.053; and R²=0.104 for p<0.05).

(E-F) Comparison of muscle-specific Te94^RNAi versus Prosβ5^RNAi indicates some overlap in the gene expression changes induced (R²=0.248; and R²=0.305 for p<0.05), similar to the comparison of Te94^RNAi versus CG6272^RNAi (R²=0.202; and R²=0.257 for p<0.05). (G) No correlation (R²=0.068, and R²=0.097 for p<0.05) is found when Te94^RNAi is compared with control GFP^RNAi. In (A-G), the identity of x and y axes is specified in the figure panels. All RNA-seq datasets are normalized to white^RNAi; GFP^RNAi serves as additional control; n = 3.

(H) Gene categories upregulated in muscle by RNAi for CG6272 (C/EBPγ) include peptidases/proteases and many other gene categories (outlined) that are similarly modulated by Prosβ1^RNAi and Prosβ5^RNAi (Fig. 1 and Supplemental Fig. 1). Genes with p<0.05 and logratio>1 were used for these analyses.

(I) Myokines that are upregulated (red) and downregulated (blue) by proteasome stress (Fig. 2A) are similarly modulated by CG6272^RNAi, including Amyrel.

(J-K) CG6272^RNAi increases Amyrel expression in skeletal muscle, similar to overexpression of slbo, homologous to C/EBPβ and C/EBPδ compared to controls (L-M); SD, n = 3.

(N) RNAi for slbo reduces Amyrel expression in Prosβ1^RNAi muscle, compared to control white^RNAi. SD, n = 3.

(O) Proteasome stress in skeletal muscle is sensed via antagonizing functions of C/EBPβ/δ (slbo) and C/EBPγ (CG6272) transcription factors, which induce a local adaptive response based on the transcriptional induction of proteases, and a systemic adaptive response via modulation of muscle-secreted factors (myokines).

Supplemental Fig. S3 reports additional data related to Fig. 3.