TRPA1 underlies a sensing mechanism for O2

Abstract

Oxygen (O(2)) is a prerequisite for cellular respiration in aerobic organisms but also elicits toxicity. To understand how animals cope with the ambivalent physiological nature of O(2), it is critical to elucidate the molecular mechanisms responsible for O(2) sensing. Here our systematic evaluation of transient receptor potential (TRP) cation channels using reactive disulfides with different redox potentials reveals the capability of TRPA1 to sense O(2). O(2) sensing is based upon disparate processes: whereas prolyl hydroxylases (PHDs) exert O(2)-dependent inhibition on TRPA1 activity in normoxia, direct O(2) action overrides the inhibition via the prominent sensitivity of TRPA1 to cysteine-mediated oxidation in hyperoxia. Unexpectedly, TRPA1 is activated through relief from the same PHD-mediated inhibition in hypoxia. In mice, disruption of the Trpa1 gene abolishes hyperoxia- and hypoxia-induced cationic currents in vagal and sensory neurons and thereby impedes enhancement of in vivo vagal discharges induced by hyperoxia and hypoxia. The results suggest a new O(2)-sensing mechanism mediated by TRPA1.

TRPV4 channel activity is modulated by direct interaction of the ankyrin domain to PI(4,5)P2

“…Fura-2 fluorescence was measured in HBS, containing 107 mM NaCl, 6 mM KCl, 1.2 mM MgSO 4 , 2 mM CaCl 2 , 11.5 mM glucose and 20 mM HEPES (pH adjusted to 7.4 with NaOH) 65,69 . Fluorescence images of the cells were recorded and analyzed with a video image analysis system (Aquacosmos; Hamamatsu Photonics), according to the manufacturer's instructions.…”

“…Fura-2 measurements were performed at 21 ± 1°C in HBS. The 340:380 ratios were converted to Ca 2 þ concentrations by in vivo calibration using 5 mM ionomycin, as described previously 65 .…”

“…Currents from cells were recorded at room temperature (22-25°C), using whole-cell mode patch-clamp techniques with an EPC-9 patchclamp amplifier (Heka Electronics), as previously described 65 . The patch electrodes were prepared from borosilicate glass capillaries and had a resistance of 2-4 MO.…”

“…The cell surface expressions of GFP-tagged TRPV4 constructs were measured by biotinylation, as previously described 65 with modifications. The cells were incubated with 0.5 mg ml À 1 Sulfo-NHS-SS-Biotin (Thermo Scientific) in PBS for 30 min at 4°C.…”

PHD3 regulates EGFR internalization and signalling in tumours

“…A number of recent reports suggest that the regulation of receptor activity and trafficking is a more general function of PHD3. PHD3 is involved in the regulation of the trafficking and activity of the b2-adrenergic receptor 17 and the TRPA1 ion channel 42 ; moreover, the Caenorhabditis elegans PHD homologue, Egl-9E, has been recently shown to regulate the trafficking of glutamate receptor 1 to the plasma membrane 43 . It is therefore tempting to speculate that the regulation of receptor trafficking may be an important function of PHD3 to flexibly respond to microenvironmental cues.…”