Members of the transient receptor potential (TRP) ion channels mediate thermosensation and mechanosensation in both vertebrates and invertebrates.TRPA-1 (C29E6.2), is the C. elegans ortholog of mouse TRPA1. We found that TRPA-1::GFP was expressed in many tissues including amphid sensory neurons, and mechanosensory neurons. The most robust behavioral abnormalities we observed in
trpa-1 mutants were related to nose touch and foraging behaviors.
Nose touch behavior is dependent on the ASH nociceptive neurons as well as at least two additional neuron classes, OLQ and FLP. We found that
trpa-1 mutants are defective for nose-touch. Cell specific rescue in ASHwas unable to rescue this defect. Conversely, a
del-2 promoter,expressed in the OLQ and IL1 neurons significantly rescued
trpa-1 nose-touch defects. Using in vivo calcium imaging we are able to confirm that nose touch responses in ASHwere not altered in
trpa-1 mutant, while OLQ neural responses showed significantly decreased calcium transients in response to nose touch.
In addition to nose touch, the OLQs, along with the IL1 neurons are required for foraging behaviors.
trpa-1 mutants fail to suppress foraging upon touch to the top of the nose or anterior body. Additionally,
trpa-1mutants foraged at a significantly slower rate than wild-type and also exhibited exaggerated head bends, phenotypes observed in worms with ablated OLQ and IL1 neurons. Cell specific rescue in the OLQ and IL1 neurons rescued these defects.
To test if cTRPA-1 could be directly activated by mechanical stimulation, we heterologously expressed cTRPA-1 in mammalian cells assayed electrophysiological responses to pressure from the recording pipet. In whole-cell recordings, we observed robust currents in response to suction stimuli. Some TRP ion channels are activated downstream of G-protein coupled receptors. Bradykinin is an inflammatory peptide that mediates pain and inflammation is able to activate mouse TRPA1. In a similar fashion, cTRPA1 is activated by bradykinin-receptor activation in CHO cells.