Characterizing the effects of siRNA against PITPβ. Quantitative data are shown as mean ± SD, with the number of independent experiments indicated. Statistics was performed using the two-tailed Student’s t test: ****P < 0.0001, ns (non-significant) P > 0.05. (A) Efficacy of siRNA against PITPβ assessed by western blotting of whole cell lysate, n = 2. β-Actin levels confirmed a similar amount of cell lysates examined. (B) COPI transport assay measuring the effect of siRNA against PITPβ and rescue using either wild-type or catalytic dead (C94A) form. Representative confocal images are shown on the left, VSVG-KDELR (green) and giantin (magenta), bar = 10 µm. The quantitation of a representative experiment is shown in the right, n = 7. (C) Transport assay assessing the effect of PITPβ depletion on the arrival of a model secretory cargo, VSVG, to the Golgi from the ER. Quantitation of a representative experiment is shown on right, n = 3. Representative confocal images are shown on left, VSVG (green) and giantin (magenta), bar = 10 µm. (D) Transport assay assessing the effect of PITPβ depletion on the transport of VSVG from the Golgi to the plasma membrane. Quantitation of a representative experiment is shown on the right, n = 3. Representative confocal images are shown on the left, VSVG (green) and TGN46 (magenta), bar = 10 µm. (E) Reduction of sPC levels in Golgi membrane upon PITPβ depletion as assessed by targeted lipidomics, n = 3. PC species are categorized based on their total acyl chain length and unsaturations. Source data are available for this figure: SourceData F2.