Journal: Frontiers in Immunology
Article Title: Integrated signaling and transcriptome analysis reveals Src family kinase individualities and novel pathways controlled by their constitutive activity
doi: 10.3389/fimmu.2023.1224520
Figure Lengend Snippet: Role of SFKs in the regulation of ER homeostasis. (A) SFK overexpression suffices to induce ER expansion in an enzymatic activity-related fashion. Lck- or Lyn-expressing cells and the -Dox counterparts were stained with ER tracker Blue-White DPX at the indicated time points after Dox addition to the cell cultures and analyzed by FACS. ER expansion measured by increases of ER tracker dye fluorescence (lower panel histograms) is correlated to increases in SFK protein levels (GFP fluorescence, upper panel histograms). 18h incubation with 30μM of the pan SFK inhibitor PP2 reduced ER expansion to baseline (-Dox) levels. The correspondent reduction of pY416 after PP2 incubation for each SFK is shown in the bottom-panel histograms. Treatment with 50 µM of the ER-stress inducer Chloroquine (CQ) for 12h was used a positive control for the expected function of the ER-tracker reagent. Graph shows the ratio of ER tracker dye MFI from Lck- or Lyn-expressing cells to -Dox treated cells. Since essentially there was no difference between the Lck and Lyn samples, statistics were calculated for the mean values between each time point (n=4, Unpaired Student t test; mean +/- SD; **P < 0.01, ***P < 0.001; ns, not significant). (B) SFK-driven ER expansion is not concurrent with upregulation of UPR mediators. RT-qPCR of the indicated UPR modulators. Each time point corresponds to samples stained with ER tracker shown in (A) RT-qPCR data are shown log 2 FC of the gene expression between Lck-BJAB (black)/-Dox and Lyn-BJAB (grey)/-Dox (n=2, Multiple unpaired Student t test; mean +/- SD; *P < 0.05, **P < 0.01, ***P < 0.001; ns: not significant). (C) SFK overexpression suffices to induce FAM134B oligomerization in an enzymatic activity-related fashion. Lck- or Lyn-expressing cells and their -Dox counterparts were mixed at a ratio of 1:1, immobilized on poly-D-lysine coated microscope slides, stained for FAM134B (white), and visualized by confocal microscopy. GFP (green) denotes the SFK-expressing cells. Sample sets include: i) untreated cells (left-hand side panels) ii) SFK-expressing cells treated with 30μM PP2 for 18h, mixed with untreated -Dox cells (right-hand side panels) to provide a comparative visualization of SFK activity influence on the cargo receptor clustering and iii) -Dox cells treated with 50 µM CQ for 12h (indicative image shown in lower panels of D, below). FAM134B oligomers within single cells, appearing as distinctive puncta, were quantified for each sample. Collective quantitation results from three independent experiments (for the untreated samples) and two independent experiments (for PP2 and CQ treatments) are displayed on the adjacent graph. Number of cells for each sample -Dox/untreated n=239, -Dox/CQ n=79, Lck-BJAB/untreated n=164, Lck-BJAB/PP2 n=98, Lyn-BJAB/untreated n=144, Lyn-BJAB/PP2 n=84. Scale bar, 5 µm (n=2, Unpaired Student t test; mean +/- standard deviation [SD]; ****P < 0.0001). (D) SFK-driven FAM134B oligomerization does not coincide with LC3 colocalization. Lck- or Lyn-expressing cells and their -Dox counterparts mixed at a ratio of 1:1 (upper panels), or -Dox cells treated with 50 µM CQ for 12h (lower panels) were immobilized on poly-D-lysine coated microscope slides, stained for FAM134B (white) and LC3B (red), and visualized by confocal microscopy. GFP (green) denotes the SFK-expressing cells. Colocalization of FAM134B and LC3 was quantified by the coloc2 pre-installed plugin of Image (J) Collective colocalization analysis results from two independent experiments are displayed on the adjacent graph. Number of cells for each sample -Dox/untreated n=116, -Dox/CQ n=116, Lck-BJAB/untreated n=76, Lyn-BJAB/untreated n=73. Scale bar, 5 µm (n=2, Unpaired Student t test; mean +/- standard deviation [SD]; ****P < 0.0001).
Article Snippet: The pan-SFK inhibitor PP2 (Calbiochem) was used at 30 μM for 18h in the humidified incubator (for treatment of samples stained with ER tracker) and at 100 μM for 10 min at 37°C (for transient SFK inhibition).
Techniques: Over Expression, Activity Assay, Expressing, Staining, Fluorescence, Incubation, Positive Control, Quantitative RT-PCR, Gene Expression, Microscopy, Confocal Microscopy, Quantitation Assay, Standard Deviation