Journal: bioRxiv
Article Title: STARD3 coordinates Endoplasmic Reticulum-late endosome/lysosome contacts and organelle positioning through a GSK3-regulated phosphorylation switch
doi: 10.1101/2025.05.29.656564
Figure Lengend Snippet: A: Schematic representation of the different STARD3 mutants used. B-E: Representative images of MCF7 cells expressing WT STARD3 (B), STARD3 S209A (C), STARD3 SD/PA (D), STARD3 t.START (E) left untreated (left) or treated with CHIR99021 (right), and labelled with an anti-STARD3 antibody (green) and with Hoechst (nuclei; blue). Scale bars: 10 µm. F: Clustering index of STARD3-positive vesicles of samples shown in B-E and . Data are displayed as Superplots showing the clustering index per cell (small dots) and its mean per independent experiment (large dots). Number of cells: STARD3-NT: 37, STARD3-CHIR99021: 37, STARD3 S209A-NT: 25, STARD3 S209A-CHIR99021: 32, STARD3 t.FFAT-NT: 40, STARD3 ts FFAT-CHIR99021: 29, STARD3 SD/PA-NT: 35, STARD3 SD/PA-CHIR99021: 28, STARD3 t.START-NT: 43, STARD3 t.START-CHIR99021: 44, from five independent experiments. Independent experiments are color-coded. Means and error bars (SD) are shown as black bars. One-way ANOVA with Tukey’s multiple comparison test(****, P < 0.0001; n = 5 independent experiments). G: Schematic representation of STARD3NL mutants used in the study. The MENTAL domain in light blue contains 4 transmembrane helices (dark blue) and a Phospho-FFAT motif (red). The chimeric construct STARD3NL-START domain is composed of STARD3NL fused to the START domain of STARD3. H-J: Representative images of MCF7 cells expressing WT STARD3NL (H), STARD3NL t.FFAT (I), and the STARD3NL-START chimeric construct (J) left untreated (left) or treated with CHIR99021 (right), and labelled with an anti-STARD3NL antibody (green) and with Hoescht-33258 (nuclei; blue). Scale bars: 10 µm. K: Clustering index of STARD3NL-positive vesicles of samples shown in H-J. Data are displayed as Superplots showing the clustering index per cell (small dots) and its mean per independent experiment (large dots). Number of cells: STARD3NL-NT: 78, STARD3NL-CHIR99021: 66, STARD3NL t.FFAT-NT: 32, STARD3NL t.FFAT-CHIR99021: 32, STARD3NL-START-NT: 33, STARD3NL-START-CHIR99021: 37, from four independent experiments). Independent experiments are color-coded. Means and error bars (SD) are shown as black bars. One-way ANOVA with Tukey’s multiple comparison test(*, P < 0.05; ****, P < 0.0001; n = 4 independent experiments). L: Schematic representation of chimeric constructs: one consisting of the TMEM192 transmembrane fragment fused to the START domain of STARD3, and another combining the amino-terminal region of LAMTOR1 with the START domain of STARD3 (referred to as Lyso-START). M-N: Representative images of MCF7 cells expressing TMEM192-START chimera (M), and Lyso-START (N), left untreated (left) or treated with CHIR99021 (right), and labelled with an anti-STARD3 antibody (green) and with Hoescht-33258 (nuclei; blue). Scale bars: 10 µm. O: Clustering index of STARD3-positive vesicles of samples shown in M-N. Data are displayed as Superplots showing the clustering index for individual cell (small dots) and the mean per independent experiment (large dots). Number of cells: STARD3-NT: 29, STARD3-CHIR99021: 24, TMEM192-START chimera-NT: 27, Lyso-START-NT: 30 from three independent experiments. Independent experiments are color-coded. Means and error bars (SD) are shown as black bars. One-way ANOVA with Dunett’s multiple comparison test(****, P < 0.0001; n = 3 independent experiments).
Article Snippet: The primary antibodies used were rabbit anti-GFP (1:1000; TP401, Torrey Pine Biolabs, RRID:AB_10013661), mouse anti-Lamp1 H4A3 (1:50; DSHB, RRID:AB_2296838), mouse anti-GSK3α/β (1/1000; Santa Cruz Biolabs; 0011-A: sc-7291, RRID:AB_2279451), mouse anti-STARD3 (3G11; 1:100; IGBMC), and rabbit anti-pS 209 STARD3 (3144; 1:200; IGBMC), rabbit anti-Tip60 (1:1000; Cell Signaling 12058, RRID:AB_2797811), rabbit anti-pS 86 Tip60 (1:1000; Abcam ab73207, RRID:AB_1523845), mouse anti-VAP-A (1:1000; 4C12, Santa Cruz Biotechnology, sc-293278), rabbit anti-VAP-B [1:1,000; kind gift from Dr. L. Dupuis (Kabashi et al, 2013)], mouse anti-MOSPD2 [1:7; 1MOS-4E10, ( )], rabbit anti-GAPDH (1:1000; Sigma-Aldrich, RRID:AB_796208).
Techniques: Expressing, Comparison, Construct