Differential regulation of proton-sensitive ion channels by phospholipids: a comparative study between ASICs and TRPV1

PLoS One. 2015 Mar 17;10(3):e0122014. doi: 10.1371/journal.pone.0122014. eCollection 2015.

Abstract

Protons are released in pain-generating pathological conditions such as inflammation, ischemic stroke, infection, and cancer. During normal synaptic activities, protons are thought to play a role in neurotransmission processes. Acid-sensing ion channels (ASICs) are typical proton sensors in the central nervous system (CNS) and the peripheral nervous system (PNS). In addition to ASICs, capsaicin- and heat-activated transient receptor potential vanilloid 1 (TRPV1) channels can also mediate proton-mediated pain signaling. In spite of their importance in perception of pH fluctuations, the regulatory mechanisms of these proton-sensitive ion channels still need to be further investigated. Here, we compared regulation of ASICs and TRPV1 by membrane phosphoinositides, which are general cofactors of many receptors and ion channels. We observed that ASICs do not require membrane phosphatidylinositol 4-phosphate (PI(4)P) or phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) for their function. However, TRPV1 currents were inhibited by simultaneous breakdown of PI(4)P and PI(4,5)P2. By using a novel chimeric protein, CF-PTEN, that can specifically dephosphorylate at the D3 position of phosphatidylinositol 3,4,5-trisphosphate (PI(3,4,5)P3), we also observed that neither ASICs nor TRPV1 activities were altered by depletion of PI(3,4,5)P3 in intact cells. Finally, we compared the effects of arachidonic acid (AA) on two proton-sensitive ion channels. We observed that AA potentiates the currents of both ASICs and TRPV1, but that they have different recovery aspects. In conclusion, ASICs and TRPV1 have different sensitivities toward membrane phospholipids, such as PI(4)P, PI(4,5)P2, and AA, although they have common roles as proton sensors. Further investigation about the complementary roles and respective contributions of ASICs and TRPV1 in proton-mediated signaling is necessary.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acid Sensing Ion Channels / metabolism*
  • Animals
  • Arachidonic Acid / metabolism*
  • HEK293 Cells
  • Humans
  • Mice
  • Phosphatidylinositol Phosphates / metabolism*
  • TRPV Cation Channels / metabolism*

Substances

  • Acid Sensing Ion Channels
  • Phosphatidylinositol Phosphates
  • TRPV Cation Channels
  • TRPV1 protein, human
  • TRPV1 protein, mouse
  • Arachidonic Acid

Grants and funding

This work was supported by the Ministry of Education, Science & Technology (No. 2012R1A1A2044699) and the DGIST R&D Program of the Ministry of Science, ICT&Future Planning (No. 14-BD-06). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.