PSD-95 interacts with NBCn1 and enhances channel-like activity without affecting Na/HCO(3) cotransport

Cell Physiol Biochem. 2012;30(6):1444-55. doi: 10.1159/000343332. Epub 2012 Nov 30.


Background/aims: The sodium/bicarbonate transporter NBCn1 plays an essential role in intracellular pH regulation and transepithelial HCO(3)(-) movement in the body. NBCn1 also has sodium channel-like activity uncoupled to Na/HCO(3) cotransport. We previously reported that NBCn1 interacts with the postsynaptic density protein PSD-95 in the brain. Here, we elucidated the structural determinant and functional consequence of NBCn1/PSD-95 interaction.

Results: In rat hippocampal CA3 neurons, NBCn1 was localized to the postsynaptic membranes of both dendritic shafts and spines and occasionally to the presynaptic membranes. A GST/NBCn1 fusion protein containing the C-terminal 131 amino acids of NBCn1 pulled down PSD-95 from rat brain lysates, whereas GST/NBCn1-ΔETSL (deletion of the last four amino acids) and GST/NBCn2 (NCBE) lacking the same ETSL did not. NBCn1 and PSD-95 were coimmunoprecipitated in HEK 293 cells, and their interaction did not affect the efficacy of PSD-95 to bind to the NMDA receptor NR2A. PSD-95 has negligible effects on intracellular pH changes mediated by NBCn1 in HEK 293 cells and Xenopus oocytes. However, PSD-95 increased an ionic conductance produced by NBCn1 channel-like activity. This increase was abolished by NBCn1-ΔETSL or by the peptide containing the last 15 amino acids of NBCn1.

Conclusion: Our data suggest that PSD-95 interacts with NBCn1 and increases its channel-like activity while negligibly affecting Na/HCO(3) cotransport. The possibility that the channel-like activity occurs via an intermolecular cavity of multimeric NBCn1 proteins is discussed.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Binding, Competitive
  • CA3 Region, Hippocampal / cytology
  • Dendritic Spines / metabolism
  • Disks Large Homolog 4 Protein
  • HEK293 Cells
  • Humans
  • Hydrogen-Ion Concentration
  • Intracellular Signaling Peptides and Proteins / metabolism*
  • Membrane Proteins / metabolism*
  • PDZ Domains
  • Peptide Fragments / metabolism
  • Protein Binding
  • Rats
  • Rats, Sprague-Dawley
  • Sodium Bicarbonate / metabolism*
  • Sodium-Bicarbonate Symporters / metabolism*
  • Synapses / metabolism
  • Xenopus


  • Disks Large Homolog 4 Protein
  • Dlg4 protein, rat
  • Intracellular Signaling Peptides and Proteins
  • Membrane Proteins
  • Peptide Fragments
  • Slc4a7 protein, rat
  • Sodium-Bicarbonate Symporters
  • Sodium Bicarbonate