Gastrointestinal Physiology - Gianrico Farrugia

Figure 1. Expression of alpha1C in human jejunum. a, Northern analysis of alpha1C from human jejunum with beta-tubulin to show relative abundance. b, alpha1C-like immunoreactivity at the periphery of smooth muscle cells. Scale bar = 10 um.

Figure 2. Shear-stress increases the current of heterologously expressed human jejunal alpha1C. a, Representative whole cell recording of an HEK293 cell expressing the human jejunal alpha1C in 80 mM Ba2+. b, The same cell during shear-stress generated by increased bath perfusion. c, Mean I-V relationships. d, Normalized mean maximal peak inward barium currents before, during and after bath perfusion (n=10, P<0.05).

Figure 3. Shear-stress increases the calcium current of coexpressed human jejunal alpha1C and beta2 subunits. a, Whole cell recording of an HEK293 cell coexpressing the human jejunal alpha1C and beta2 subunits in normal Ringer solution. b, Same cell during shear-stress generated by bath perfusion at 10 ml/min. c, Mean I-V relationships. d, Normalized mean maximal peak inward calcium currents for the same cells before, during and after bath perfusion (n=15, P<0.05).

Figure 4. Shear-stress effects on activation and inactivation. a, Representative whole cell recording of an HEK293 cell coexpressing the human jejunal alpha1C and beta2 subunits unperfused, during shear-stress generated by bath perfusion (10 ml/min) and the difference current. b, Activation kinetics reported as time to peak. Time to peak for perfusion is faster than control from -25 to +25 mV and time to peak for difference current is faster than control from -25 to +30 mV (n=15, P<0.05) c, Tau of inactivation is significantly smaller for perfusion than control from -20 to +5 mV and smaller for the difference current than control current from -20 to +15 mV (n=15, P<0.05).

Figure 5. Positive pressure increases the current of heterologously coexpressed human jejunal alpha1C and beta2 subunits. a, Whole cell recording of an HEK293 cell coexpressing the human jejunal alpha1C and beta2 subunits. b, Same cell during increased membrane tension as a result of 5 mmHg pipette positive pressure. c, Mean I-V relationships. d, Normalized mean maximal peak inward calcium currents for the same cells before, during and after bath perfusion (n=6, P<0.05).

Figure 6. Negative pressure increases single channel opening of alpha1C. Representative single channel recording of an HEK293 cell coexpressing the human jejunal alpha1C and beta2 subunits at baseline and with -40 mmHg of negative pressure (C = closed, O = open). Eight cells showed similar opening characteristics.

Figure 7. Human cardiac alpha1C is mechanosensitive. a, Whole cell recording of an HEK293 cell cotransfected with the human cardiac alpha1C and human jejunal beta2 subunits. b, Same cell during shear-stress generated by 10 ml/min bath perfusion. c, Mean I-V relationships. d, Normalized mean maximal peak inward calcium currents for the same cells before, during and after bath perfusion (n=11, P<0.05).

Figure 8. alpha1C mechanosensitivity is not mediated by the C-terminus. a, Representative whole cell recording of an HEK293 cell cotransfected with the 1703 C-terminal truncated alpha1C and beta2 subunits. b, Same cell during shear-stress (10 ml/min). c, Mean I-V relationships. d, Normalized mean maximal peak inward calcium currents for the same cells before, during and after bath perfusion (n=11, P<0.05)