Fig. 8: The absence of Emr1 affects the synthesis of phosphatidylethanolamine.

a Thin-layer chromatography (TLC) assays. TLC analysis of phospholipids extracted from WT and emr1Δ cells (whole-cell lysates). Phosphatidylserine (PS), phosphatidylethanolamine (PE), and cardiolipin (CL) were used as lipid standards (indicated by arrows). b Quantification of CL, PE, and PS shown in a. The band intensity of emr1Δ cells was normalized to the one of WT cells (displayed as Ratio). Data from five independent experiments were used for the quantification (indicated by dots). Error bars represent confidence intervals (95%), and the center of the error bar is the mean. Two-sided single-group Student’s t-test was used to calculate the p-values of log ratio for each type of phospholipids (PS, p = 0.537; PE, p = 0.008; CL, p = 0.024). c TLC analysis of phospholipids extracted from isolated mitochondria of WT and emr1Δ cells. Arrows indicate lipid standards. d Quantification of CL, PE, and PS shown in c. The band intensity of emr1Δ cells was normalized to the one of WT cells (displayed as Ratio). Data from four independent experiments were used for the quantification (indicated by dots). Error bars represent confidence intervals (95%), and the center of the error bar is the mean. Two-sided Single-group Student’s t-test was used to calculate the p-values of log ratio for each type of phospholipids (PS, p = 0.222; PE, p = 0.025; CL, p = 0.546). e Growth assays for the indicated cells. The indicated cells were spotted on YE5S plates containing glucose after tenfold serial dilution. Diagram showing the routes of PE synthesis. (1) The PS decarboxylase Psd1 resides in mitochondria to convert PS to PE after PS is transferred from the ER to mitochondria through the contact sites between the ER and mitochondria; (2) the PS decarboxylases Psd2 and Psd3 likely resides in other cellular compartments (except mitochondria) to synthesize PE; (3) Ept1 in the Kennedy pathway promotes the synthesis of PE. Note that psd2Δ, psd3Δ, and ept1Δ, but not psd1Δ, had an additive growth defect with emr1Δ (highlighted by red rectangles).