Figure 2.

Targeting of Small Human Presecretory Proteins to the Sec61 Complex in the ER Membrane Involves Various Pathways

(A) Effects of Sec61α1 depletion on transport of ppl, Sec61ß, ppa, and ps under co- or post-translational conditions.

(B) Effects of SR depletion on transport of ppl, Sec61ß, ppa plus variants (in red), and ps plus variants under co- or post-translational conditions.

(C) Effects of HSND2 and/or Wrb depletion on transport of ppl, Sec61ß, ppa, and ps under co- or post-translational conditions.

(D) Effects of Sec62 depletion on transport of ppl, Sec61ß, ppa plus variants (in red), and ps plus variants under co- or post-translational conditions.

(E) Protein content of the indicated HeLa cells relative to β-actin was validated by western blot using the indicated antibodies and the control sample was set to 100%.

In (A)–(D), prior to preparation of semipermeabilized cells, HeLa cells were treated with the indicated siRNA(s) (Table S3). Precursors were co- (co) or post-translationally (post) incubated with the indicated ER membranes. Radioactive samples were subjected to SDS-PAGE and phosphorimaging. Targeting efficiencies were calculated as the proportion of N-glycosylation and/or signal peptide cleavage of the total amount of synthesized precursors with the control sample set to 100%.

Shown are individual data points of at least three independent experiments and the mean. Statistical significance (^∗∗∗p < 0.001, ^∗∗p < 0.01, ^∗p < 0.05) was tested by Student’s t test (upper panel) or using ANOVA plus post hoc Dunnett or Newman-Keuls multiple comparison test (horizontal brackets).

See also Figure S2.