DNM inhibition affects ITGB1 activity and Rab11 cell distribution in human MKs. (A-B) Quantification of active ITGB1 at the surface of MKs. Representative flow cytometry histograms (A) and flow cytometry quantification (B) in 3 experiments measuring active ITGB1 at the surface of MKs after 2 hours on FN. ITGB1 activation was decreased by 17% in DNSR-treated MKs, when compared with control (CTRL) cells (paired Student t test P = .001). (C) Rab11 staining distribution in MKs on FN. MKs were stained with an antibody directed against Rab11 (green), a marker of recycling endosomes, and against activated ITGB1 (red). The nucleus is stained in blue. In the MKs that had not spread, Rab11 staining was more centrally clustered (arrow) in DNSR-treated cells, suggesting a decreased recycling process when compared with CTRL cells. Twenty-five or more primary MKs were analyzed. Images taken by Nikon A1R+ confocal microscope; original magnification, 60× Plan-Apochromat oil immersion lens. Scale bars represent 5 µm. (D-E) Quantification of active ITGB1 at the surface of CHRF cells transduced with nontargeting control or with shRNAs against DNM2 and DNM3. Representative flow cytometry histograms and flow cytometry quantification in 3 experiments in CHRF cells, activated with PMA (1 µM) and stained with an antibody specific for active ITGB1. Active surface ITGB1 in CHRF cells with shDNM2 and shDNM3 knockdown was reduced down to levels of 80% of CTRL cells. (F-G) Quantification of active ITGB1 at the surface of MEG-01 cells transduced with empty vector or with wild-type rat Dnm2 or human DNM3 or with DNM mutants. Flow cytometry representative histograms and quantification in 4 experiments in MEG-01 cells, activated with PMA (1 µM) and stained with an antibody specific for active ITGB1. In MEG-01 cells transduced with dominant-negative Dnm2-K44A or with truncated GTPase-less DNM3, active ITGB1 was reduced when compared with CTRL cells. Error bars indicate standard errors of the mean of ≥3 independent experiments. *P ≤ .05.