Fig. 2: Ca2+ and PtdIns(4,5)P2 binding in hTRPM4.
From: Structural landscape of activation, desensitization and inhibition in the human TRPM4 channel
a, Ca2+-PtdIns(4,5)P2-activated TRPM4. The front subunit, with bound Ca2+ (green spheres) and PtdIns(4,5)P2 (gold sticks), is highlighted in blue cartoon representation. b, Zoomed-in view of the transmembrane Ca2+-binding site. c, Ca2+-activated outward currents of wild-type TRPM4 and its transmembrane Ca2+-site mutants in the steady state without PtdIns(4,5)P2. Currents were recorded at +100 mV in inside-out patches with 300 µM Ca2+ in the bath (cytosolic). d, Zoomed-in view of the intracellular Ca2+-binding site. e, Ca2+-activated outward currents of wild-type TRPM4 and its intracellular Ca2+-site mutants in the steady state without PtdIns(4,5)P2. Currents were recorded at +100 mV in inside-out patches with 300 µM Ca2+ in the bath (cytosolic). f, Zoomed-in view of the PtdIns(4,5)P2-binding site. PtdIns(4,5)P2 and its interacting residues are shown in stick representation. PtdIns(4,5)P2 density (gray surface) is contoured at 0.17 in ChimeraX. g, PtdIns(4,5)P2-potentiated outward currents of wild-type TRPM4 and its PtdIns(4,5)P2-site mutants. Currents were recorded at +100 mV in inside-out patches with 300 μM Ca2+ and 10 μM PtdIns(4,5)P2 diC8 in the bath. h, Structural comparison at the PtdIns(4,5)P2-binding site between the open (blue) and closed (wheat) TRPM4, showing the conformational changes of W864 and Y1057 with their side chains colored in cyan (open state) or yellow (closed state). The red numbers mark the C4 and C5 positions of inositol. For data in c,e,g, bars represent the mean ± s.d. of n = 5 independent replicates (shown as dots). P values were calculated using a two-sided Student’s t-test. **P < 0.01.
