Fig. 4.

PS synthesis at ER-endosome contacts increases PS transport to endosomes. A: Growing cells expressing FFAT-GFP-PssA and the ER marker, ds-Red-HDEL, were visualized live. Scale bar = 5 μm. B: PS synthase activities of lysates from the indicated strains (mean ± SD, n = 3 independent experiments). C: The indicated strains were labeled with [³H]serine for 30 min and the percentage of [³H]PS converted to [³H]PE was determined (mean ± SD, n  =  3 independent experiments). *P < 0.05, independent two-tailed t-test. Raw data used to calculate percent of [³H]PS converted to [³H]PE is in supplemental Fig. S2E, F.