Alternatively spliced isoforms of TRIP8b differentially control h channel trafficking and function

Area of Science:

• Neuroscience
• Molecular Biology
• Channelopathies

Background:

• Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels generate the I(h) current, crucial for neuronal excitability.
• Mechanisms controlling HCN channel localization and function, including auxiliary proteins, are not fully understood.

Purpose of the Study:

• Investigate the role of TRIP8b, an HCN channel-interacting protein, and its splice variants in regulating HCN channel function.
• Determine the impact of TRIP8b isoforms on HCN channel trafficking, surface expression, and I(h) current density.

Main Methods:

• Coexpression of HCN1 and TRIP8b splice variants in heterologous cells.
• Analysis of I(h) gating and current density.
• Assessment of HCN1 surface expression and localization in hippocampal neurons.
• shRNA-mediated knockdown of TRIP8b in hippocampal neurons.

Main Results:

• TRIP8b splice variants modulate HCN1 gating and differentially affect I(h) current density and surface expression.
• Isoform-specific changes in HCN1 localization were observed in hippocampal neurons.
• Predominant brain TRIP8b isoforms enhance HCN channel surface expression.
• TRIP8b knockdown significantly reduced native I(h) in hippocampal neurons.

Conclusions:

• TRIP8b splice variants play a critical role in regulating HCN channel surface expression and function.
• The primary role of TRIP8b in the brain is to promote HCN channel surface expression and enhance I(h).
• TRIP8b may be involved in normal neuronal function and aberrant excitability in neurological diseases like epilepsy.