Distinct retrograde microtubule motor sets drive early and late endosome transport (2020)
Figure 1

Figure 1. STIM1 forms a triple protein complex with p150Glued and EB1 to promote dynactin loading at MT plus ends.

(A) Representative Western Blot analysis of the endogenous p150Glued co-immunoprecipitated with EB1 in shCTL or shSTIM1 ECs (left) and its quantification by normalized densitometry (right). Negative control (CTL) was performed incubating cell lysate with protein A- or G-Sepharose and empty mouse IgG. Results are the average ± SD of three independent assays. shCTL value of each biological replicate was normalized on itself and so shSTIM1 experimental value. Results were analyzed by a parametric two-tailed analysis of variance (ANOVA) with Bonferroni post hoc analysis. ANOVA p≤ 0,001; Bonferroni for shCTL and shSTIM1 p≤ 0,05 *.

(B) Representative of three Western Blot analysis of endogenous p150Glued, light-intermediate chain (LIC) of cytoplasmic dynein 1 and EB1 immunoprecipitated with STIM1 in wild-type ECs. Negative control (CTL) was performed incubating cell lysate with protein A- or G-Sepharose and empty rabbit IgG.

(C) Schematic model of the molecular interactions among STIM1, EB1 and p150Glued at the MT plus ends. Black arrows point at already known binding motifs, whereas red parts show interaction domains studied in this manuscript. TM = transmembrane domain. Differentially colored labels with bars correspond to the purified protein fragment with its tag and molecular weight in kDa.

(D) Representative Western Blot analysis of increasing amount of GST-STIM1 (cytoplasmic domain) pulled down by Cap-Gly-CC1-p150Glued-V5-coated beads, in absence or presence of FLAG-EB1 C-terminal. Colors label the protein as in (c). Negative control was performed using equal amount of empty GST protein, together with Cap-Gly-CC1-p150Glued.

(E) Representative Western Blot analysis of mCherry-p150Glued WT co-immunoprecipitated with GFP-STIM1 WT, NN, ΔCC1-3/WT (ΔCC/WT) or ΔCC1-3/NN (ΔCC/NN) in co-transfected HEK 293T cells. Negative control (CTL) was performed incubating cell lysate from HEK 293T co-transfected with an empty GFP vector together with mCherry-P150Glued WT with pre-cleared protein A or G-Sepharose and the rabbit GFP antibody. Below, its quantification by normalized densitometry. Results are the average ± SD of three independent assays. The value of P150Glued co-immunoprecipitated with GFP-STIM1 WT from each biological replicate was normalized on itself and so those immunoprecipitated with GFP-STIM1 NN, ΔCC/WT or ΔCC/NN. Results were analyzed by a parametric two-tailed analysis of variance (ANOVA) with Bonferroni post hoc analysis. ANOVA p≤ 0,001; Bonferroni for STIM1 WT and NN p> 0.05 not significant (ns), for STIM1 WT and ΔCC/WT p> 0.05 not significant (ns) and for STIM1 WT and ΔCC/NN p≤ 0,05 *.

(F) Representative Western Blot analysis of GST-STIM1 (cytoplasmic domain) pulled down by Cap-Gly-CC1-p150Glued-V5-coated beads, in presence of FLAG-EB1 C-terminal WT or ΔY. Negative control was performed using equal amount of empty GST protein, together with Cap-Gly-CC1-p150Glued.

(G) Confocal microscopy analysis of wild-type ECs, transiently transfected with GFP-STIM1 WT or, NN or ΔCC1-3/WT (ΔCC/WT) together with mCherry-P150Glued. Scale bar = 10 μm. Right insets are shown to highlight MT-bound p150Glued+ punctae (arrows), colocalized with STIM1. Scale bar = 5 μm.

(H) Average number of the mCherry-P150Glued+ punctae in the same cells as in (g). Counts are the average ± SEM of three independent experiments for a total of 150 punctae (30 cells). Results were analyzed by a parametric two-tailed analysis of variance (ANOVA) with Bonferroni post hoc analysis. ANOVA p≤ 0,001; Bonferroni for STIM1 WT and NN p≤ 0,001 *** and for STIM1 WT and ΔCC/WT p> 0.05 not significant (ns).

(I) Co-localization analysis of mCherry-P150Glued with GFP-STIM1 WT, NN or ΔCC1-3/WT (ΔCC/WT), transiently co-transfected in ECs, as in (g). Results are the average ± SEM of three independent experiments for a total of 150 punctae (30 cells) and analyzed by a parametric two-tailed analysis of variance (ANOVA) with Bonferroni post hoc analysis. ANOVA p≤ 0,001; Bonferroni for STIM1 WT and NN p≤ 0,001 *** and for STIM1 WT and ΔCC/WT p> 0.05 not significant (ns).