Journal: bioRxiv
Article Title: Phospholipase D1 and Phosphatidic Acid are required for MVE Fusion and Exosome Secretion
doi: 10.64898/2026.01.21.700874
Figure Lengend Snippet: (A) Normalized fusion event frequencies under pharmacological and genetic modulation of PLD activity. A549 cells were transiently transfected with CD63-pHmScarlet and GFP-PASS, then treated with DMSO (control), the PLD1 inhibitor VU00155069 (PLD1i), or the dual PLD1/PLD2 inhibitor FIPI. Separately, cells were transfected with control siRNA, PLD1 siRNA, or a combination of PLD1 and PLD2 siRNAs. Fusion frequency was calculated as the number of fusion events per 100-second movie, then normalized to the control condition within each experimental day. Fusion frequencies were significantly reduced under PLD1i (*** p < 0.001), FIPI (** p < 0.01), PLD1 knockdown (* p < 0.05), and PLD1/2 knockdown (** p < 0.01) compared to their respective controls. (B) Quantification of membrane-proximal CD63 vesicle density at the plasma membrane. A549 cells co-expressing CD63-pHmScarlet and GFP-PASS were treated with 50 mM NH 4 Cl and imaged using TIRFM to enhance visualization. Membrane-proximal vesicles were defined as CD63-positive puncta visible in the TIRF field and detected using a custom MATLAB script employing bandpass filtering and intensity thresholding. Vesicle density was significantly reduced in PLD1i ( p = 0.014) and PLD1/2i ( p = 0.0299) conditions compared to DMSO. Each data point represents the vesicle density per cell area across three independent experiments. Cell counts: DMSO, n = 37; PLD1i, n = 39; PLD1/2i, n = 36. (C) Quantification of membrane-proximal lysosome density. A549 cells expressing CD63-pHluorin were stained with Magic Red and imaged by TIRFM. Cells were selected based on CD63-pHluorin expression. Membrane-proximal lysosomes were defined as Magic Red-positive puncta and detected using the same MATLAB-based analysis as in (B). Lysosome density was significantly increased under PLD1i ( p = 0.0028) but not significantly altered under PLD1/2i ( p = 0.2897) compared to DMSO. Each data point reflects the mean lysosome density per cell from three independent experiments ( n = 47 for all conditions). Statistical comparisons were performed using one-way ANOVA .
Article Snippet: The CD63-pHmScarlet construct was generated by modifying pCMV-Sport6-CD63-pHluorin (Addgene plasmid #130901, , replacing the pHluorin tag with pHmScarlet.
Techniques: Activity Assay, Transfection, Control, Knockdown, Membrane, Clinical Proteomics, Expressing, Staining