Modulation of the transient receptor potential channel TRPA1 by phosphatidylinositol 4,5-biphosphate manipulators

The transient receptor potential channel of the ankyrin-binding repeat subfamily, TRPA1, is a Ca2+-permeable non-selective cation channel that depolarizes the plasma membrane and causes Ca2+ influx. A typical feature of TRPA1 is its rapid desensitization following activation by agonists such as mustard oil (MO), cinnamaldehyde, and a high intracellular Ca2+ concentration. In whole-cell recordings on Chinese hamster ovary (CHO) cells expressing TRPA1, desensitization was delayed when phosphatidylinositol 4,5-biphosphate (PIP2) was supplemented via the patch pipette, whereas the PIP2 scavenger neomycin accelerated desensitization. Preincubation with the PI-4 kinase inhibitor wortmannin reduced both constitutive TRPA1 channels activity and the response to MO. Run down was also accelerated by high intracellular Mg2+ concentrations, whereas chelating intracellular Mg2+ with 10 mM ethylenedinitrilotetraacetic acid (EDTA) increased the basal channel activity. In inside-out patches, we observed a rapid run down of TRPA1 activity, which could be prevented by application of diC8-PIP2 or 2 mM Mg-ATP but not Na-2-ATP to the cytosolic side of the excised patches. In isolated trigeminal ganglion neurons, preincubation with wortmannin resulted in inhibition of endogenous TRPA1 activation by MO. Taken together, our data indicate that PIP2 modulates TRPA1, albeit to a lesser extent than other known PIP2-dependent TRP channels, and that tools modifying the plasma membrane PIP2 content often have direct effects on this channel.