Fig. 4: VFT of GB1 is responsible for the interaction between GABA_B receptor and integrin β₃, and the mechano-activation of GABA_B receptor.

a Schematic representation of GABA_B-ΔVFT truncation, in which GB1 subunit lacks of the VFT domain (GB1-ΔVFT), but retains the ability to be activated by positive allosteric modulator Rac BHFF (yellow square). Co-immunoprecipitation experiments were performed using anti-HA antibody targeting to the HA tag, which is fused in the N-terminal of GB1 or GB1-ΔVFT. b Co-immunoprecipitation of GABA_B receptor or GABA_B-ΔVFT and integrin β₃ using anti-HA antibody. Blots are from one representative of five biologically independent experiments. c IP₁ production in cells transfected with GABA_B receptor, or GABA_B-ΔVFT, along with G_qi9 under suspension or adhesion conditions. Data are present as mean ± s.e.m. from four biologically independent experiments each performed in triplicates and analyzed using unpaired t test (two-tailed) to determine significance. *P < 0.05, not significant (ns) > 0.05. d Real-time recording of intracellular Ca²⁺ release in HEK293 cells expressing GABA_B-ΔVFT and G_qi9. After recording the basal state of Ca²⁺ release for 50 seconds, cells were subjected to shear stress for 100 seconds. Shear stress was then halted for 150 seconds, after which Rac BHFF was added for 200 seconds. Data are present as mean ± s.e.m. from 135 cells recorded.