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

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.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-?ETSL (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-?ETSL or by the peptide containing the last 15 amino acids of NBCn1.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.
Mesh Terms:
Animals, Binding, Competitive, CA3 Region, Hippocampal, Dendritic Spines, Disks Large Homolog 4 Protein, HEK293 Cells, Humans, Hydrogen-Ion Concentration, Intracellular Signaling Peptides and Proteins, Membrane Proteins, PDZ Domains, Peptide Fragments, Protein Binding, Rats, Rats, Sprague-Dawley, Sodium Bicarbonate, Sodium-Bicarbonate Symporters, Synapses, Xenopus
Cell Physiol Biochem
Date: Nov. 28, 2012
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