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A role for DPPX modulating external TEA sensitivity of Kv4 channels
Olaia Colinas1, Francisco D Pérez-Carretero, José R López-López
1Departamento de Bioquímica y Biología Molecular y Fisiología e Instituto de Biología y Genética Molecular (IBGM), Universidad de Valladolid y Consejo Superior de Investigaciones Científicas (CSIC), 47003 Valladolid, Spain.
The Journal of General Physiology
|April 16, 2008
Summary
Dopamine- and cyclic AMP-regulated phosphoprotein (DPPX) is crucial for oxygen-sensitive K(O2) currents in rabbit carotid body (CB) chemoreceptor cells. DPPX association with Shal-type (Kv4) channels alters their properties and enhances tetraethylammonium (TEA) sensitivity.
Area of Science:
- Neuroscience
- Molecular Biology
- Physiology
Background:
- Shal-type (Kv4) channels mediate vital K+ currents in various tissues, including neurons, heart, and carotid body (CB) chemoreceptors.
- Kv4 channel function is highly variable due to complex regulation by ancillary subunits like KChIPs and DPPX.
- DPPX is known to be integral to neuronal (I(SA)) and cardiac (I(TO)) currents.
Purpose of the Study:
- To investigate the presence and functional role of DPPX in rabbit CB chemoreceptor oxygen-sensitive K(O2) currents.
- To determine if DPPX binding modifies Kv4 channel properties, particularly tetraethylammonium (TEA) sensitivity.
- To explore the impact of DPPX on Kv4 channel kinetics and pharmacology.
Main Methods:
- Functional knockdown of DPPX using small interfering RNA (siRNA) in rabbit CB chemoreceptor cells.
- Coexpression of Kv4 subunits with DPPX in heterologous systems.
- Electrophysiological recordings to analyze K(O2) currents and TEA sensitivity.
- Assessment of kinetic effects of TEA on Kv4-DPPX heteromultimers.
Main Results:
- DPPX is present and functionally contributes to K(O2) currents in rabbit CB chemoreceptor cells.
- DPPX association with Kv4 channels significantly increases tetraethylammonium (TEA) sensitivity.
- TEA application to Kv4-DPPX complexes induces kinetic alterations, suggesting enhanced closed-state inactivation.
- DPPX binding modifies the pharmacological profile of Kv4 channels.
Conclusions:
- DPPX proteins are integral components of oxygen-sensitive K(O2) currents in CB chemoreceptor cells.
- DPPX association with Kv4 subunits modulates the pharmacological properties, specifically TEA sensitivity, of these channels.
- The findings highlight DPPX as a key regulator of Kv4 channel function in chemosensation.
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