Phosphatidylinositol-3,5-bisphosphate lipid-binding-induced activation of the human two-pore channel 2

Cell Mol Life Sci. 2018 Oct;75(20):3803-3815. doi: 10.1007/s00018-018-2829-5. Epub 2018 Apr 28.


Mammalian two-pore channels (TPCs) are activated by the low-abundance membrane lipid phosphatidyl-(3,5)-bisphosphate (PI(3,5)P2) present in the endo-lysosomal system. Malfunction of human TPC1 or TPC2 (hTPC) results in severe organellar storage diseases and membrane trafficking defects. Here, we compared the lipid-binding characteristics of hTPC2 and of the PI(3,5)P2-insensitive TPC1 from the model plant Arabidopsis thaliana. Combination of simulations with functional analysis of channel mutants revealed the presence of an hTPC2-specific lipid-binding pocket mutually formed by two channel regions exposed to the cytosolic side of the membrane. We showed that PI(3,5)P2 is simultaneously stabilized by positively charged amino acids (K203, K204, and K207) in the linker between transmembrane helices S4 and S5 and by S322 in the cytosolic extension of S6. We suggest that PI(3,5)P2 cross links two parts of the channel, enabling their coordinated movement during channel gating.

Keywords: Electrophysiology; Homology model; Ion channel; Ligand-binding; Molecular dynamics simulation; Site-directed mutagenesis.

MeSH terms

  • Amino Acid Sequence
  • Arabidopsis / metabolism
  • Arabidopsis Proteins / chemistry
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / metabolism
  • Binding Sites
  • Calcium Channels / chemistry
  • Calcium Channels / genetics
  • Calcium Channels / metabolism*
  • Humans
  • Molecular Dynamics Simulation
  • Mutagenesis, Site-Directed
  • Patch-Clamp Techniques
  • Phosphatidylinositol Phosphates / chemistry
  • Phosphatidylinositol Phosphates / metabolism*
  • Protein Structure, Tertiary
  • Protoplasts / metabolism
  • Sequence Alignment


  • Arabidopsis Proteins
  • Calcium Channels
  • Phosphatidylinositol Phosphates
  • TPCN1 protein, human
  • TPCN2 protein, human
  • phosphatidylinositol 3,5-diphosphate