Figure 5.

PIP₂ has no effect on channel activity. A, PIP₂ (PI(4,5)P₂ diC8; 25 μm) was without effect on constitutive TRP activity (n = 7). B, PIP₂ applied to a patch from a fly expressing the Kir2.1 inward rectifying K⁺ channel on a wt background opened this channel. TRP and TRPL were kept silent by the presence of ATP plus the TRP blocker La³⁺ (40 μm). The basal activity corresponds to Kir2.1 opening events. (n = 7). C, Patch from the mutant norpA (lacks PLC) presumably having high PIP₂ levels was silent and became activated by DAG (n = 4).