Regulation of HCN channel surface expression by a novel C-terminal protein-protein interaction.
Hyperpolarization-activated cation currents (I(h)) are carried by channels encoded by a family of four genes (HCN1-4) that are differentially expressed within the brain in specific cellular and subcellular compartments. HCN1 shows a high level of expression in apical dendrites of cortical pyramidal neurons and in presynaptic terminals of cerebellar basket ... cells, structures with a high density of I(h). Expression of I(h) is also regulated by neuronal activity. To isolate proteins that may control HCN channel expression or function, we performed yeast two-hybrid screens using the C-terminal cytoplasmic tails of the HCN proteins as bait. We identified a brain-specific protein, which has been previously termed TRIP8b (for TPR-containing Rab8b interacting protein) and PEX5Rp (for Pex5p-related protein), that specifically interacts with all four HCN channels through a conserved sequence in their C-terminal tails. In situ hybridization and immunohistochemistry show that TRIP8b and HCN1 are colocalized, particularly within dendritic arbors of hippocampal CA1 and neocortical layer V pyramidal neurons. The dendritic expression of TRIP8b in layer V pyramidal neurons is disrupted after deletion of HCN1 through homologous recombination, demonstrating a key in vivo interaction between HCN1 and TRIP8b. TRIP8b dramatically alters the trafficking of HCN channels heterologously expressed in Xenopus oocytes and human embryonic kidney 293 cells, causing a specific decrease in surface expression of HCN protein and I(h) density, with a pronounced intracellular accumulation of HCN protein that is colocalized in discrete cytoplasmic clusters with TRIP8b. Finally, TRIP8b expression in cultured pyramidal neurons markedly decreases native I(h) density. These data suggest a possible role for TRIP8b in regulating HCN channel density in the plasma membrane.
Mesh Terms:
Action Potentials, Amino Acid Motifs, Amino Acid Sequence, Animals, Brain, Cells, Cultured, Conserved Sequence, Cricetinae, Gene Expression Regulation, Humans, Ion Channels, Membrane Proteins, Mice, Mice, Knockout, Molecular Sequence Data, Nerve Tissue Proteins, Protein Binding, Protein Isoforms, Protein Transport, Pyramidal Cells, Rats, Rats, Sprague-Dawley, Recombinant Fusion Proteins, Sindbis Virus, Xenopus laevis
Action Potentials, Amino Acid Motifs, Amino Acid Sequence, Animals, Brain, Cells, Cultured, Conserved Sequence, Cricetinae, Gene Expression Regulation, Humans, Ion Channels, Membrane Proteins, Mice, Mice, Knockout, Molecular Sequence Data, Nerve Tissue Proteins, Protein Binding, Protein Isoforms, Protein Transport, Pyramidal Cells, Rats, Rats, Sprague-Dawley, Recombinant Fusion Proteins, Sindbis Virus, Xenopus laevis
J. Neurosci.
Date: Nov. 24, 2004
PubMed ID: 15564593
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