Figure 3. Loss of Cideb specifically inhibits loading of SREBP/SCAP into COPII vesicles.

1. Decreased SREBP‐1/2 and SCAP levels in Golgi apparatus in Cideb ^−/− mice. IB of organelle fractions of the indicated proteins and quantification of IB data from three independent experiments.
2. Cideb deficiency impairs the packaging of SCAP/SREBP into COPII vesicles. Protein present in the vesicle or microsome fractions obtained from WT or Cideb ^−/− liver was detected by IB. Quantification of IB data from three independent experiments.
3. Schematic of the BioID assay with Sar1A‐BirA*.
4. Cideb depletion decreases the recruitment of SCAP to the COPII machinery in cells. Primary hepatocytes transfected with control or Cideb siRNA were infected with adenovirus expressing Sar1A‐Flag‐BirA*. Cells were cultured in sterol‐depleted medium and treated with 80 μM biotin, prior to pull down with streptavidin‐conjugated beads. The biotinylated proteins were detected by IB with the indicated antibodies following SDS–PAGE.
5. Cleaved SREBP bypasses Cideb deficiency. WT and Cideb ^−/− mice were injected with adenovirus expressing GFP, SREBP‐1c full length (FL), or SREBP‐1c active form (N). Mice were sacrificed 7 days after injection, and liver TAG levels and hepatic expression SREBP‐1 target genes in the indicated groups were determined (n = 5 per group).

Data information: Data represent the Mean ± SEM; NS: not significant; *P < 0.05; **P < 0.01; ***P < 0.001, by 2‐tailed Student's t‐test.Source data are available online for this figure.