Related Experiment Video
Updated: Jun 12, 2026
Isolation and Kv Channel Recordings in Murine Atrial and Ventricular Cardiomyocytes
Published on: March 12, 2013
The membrane protein MiRP3 regulates Kv4.2 channels in a KChIP-dependent manner
Daniel I Levy1, Egle Cepaitis, Sherry Wanderling
1Department of Medicine, Biological Sciences Division, Pritzker School of Medicine, University of Chicago, Chicago, IL 60637, USA. dlevy@medicine.bsd.uchicago.edu
Abstract:
MiRP3, the single-span membrane protein encoded by KCNE4, is localized by immunofluorescence microscopy to the transverse tubules of murine cardiac myocytes. MiRP3 is found to co-localize with Kv4.2 subunits that contribute to cardiac transient outward potassium currents (I(to)). Whole-cell, voltage-clamp recordings of human MiRP3 and Kv4.2 expressed in a clonal cell line (tsA201) reveal MiRP3 to modulate Kv4.2 current activation, inactivation and recovery from inactivation. MiRP3 shifts the half-maximal voltage for activation (V(1/2)) approximately 20 mV and slows time to peak approximately 100%. In addition, MiRP3 slows inactivation approximately 100%, speeds recovery from inactivation approximately 30%, and enhances restored currents so they 'overshoot' baseline levels. The cytoplasmic accessory subunit KChIP2 also assembles with Kv4.2 in tsA201 cells to increase peak current, shift V(1/2) approximately 5 mV, slow time to peak approximately 10%, slow inactivation approximately 100%, and speed recovery from inactivation approximately 250% without overshoot. Simultaneous expression of all three subunits yields a biophysical profile unlike either accessory subunit alone, abolishes MiRP3-induced overshoot, and allows biochemical isolation of the ternary complex. Thus, regional heterogeneity in cardiac expression of MiRP3, Kv4.2 and KChIP2 in health and disease may establish the local attributes and magnitude of cardiac I(to).
Insights
MiRP3, a protein regulating cardiac potassium currents, modulates Kv4.2 channel activity. Its interaction with KChIP2 influences cardiac electrical function and may vary in disease.
Area of Science:
- Cardiovascular Physiology
- Molecular Biology
- Ion Channel Function
Background:
- MiRP3 (KCNE4) is a membrane protein found in cardiac myocytes.
- MiRP3 co-localizes with Kv4.2 subunits, crucial for cardiac transient outward potassium currents (I(to)).
Purpose of the Study:
- To investigate the functional effects of MiRP3 on Kv4.2 potassium channel activity.
- To compare the modulatory roles of MiRP3 and KChIP2 on Kv4.2.
- To understand the combined effects of MiRP3, Kv4.2, and KChIP2 on cardiac ion channel function.
Main Methods:
- Immunofluorescence microscopy to determine MiRP3 localization in murine cardiac myocytes.
- Whole-cell, voltage-clamp recordings in tsA201 cells expressing human MiRP3, Kv4.2, and KChIP2.
- Biochemical isolation of protein complexes.
Main Results:
- MiRP3 significantly alters Kv4.2 current activation, inactivation, and recovery kinetics, shifting voltage dependence and slowing activation and inactivation.
- KChIP2 also modulates Kv4.2 currents, increasing peak current and altering kinetics differently than MiRP3.
- Co-expression of MiRP3, Kv4.2, and KChIP2 results in a unique biophysical profile, abolishing MiRP3-induced current overshoot.
Conclusions:
- MiRP3 and KChIP2 act as accessory subunits that distinctly modulate Kv4.2 channel function.
- The interplay between MiRP3, Kv4.2, and KChIP2 is critical for shaping cardiac I(to).
- Regional differences in the expression of these subunits may underlie local variations in cardiac electrical properties in health and disease.
More Related Videos
10:22Reconstitution of a Kv Channel into Lipid Membranes for Structural and Functional Studies
Published on: July 13, 2013
11:42Reconstitution of a Transmembrane Protein, the Voltage-gated Ion Channel, KvAP, into Giant Unilamellar Vesicles for Microscopy and Patch Clamp Studies
Published on: January 22, 2015
Related Concept Videos
01:19Ion Channels
Ion channels are specialized integral membrane proteins on the plasma membrane that allow specific...
01:26Voltage-gated Ion Channels
Generally, all voltage-gated ion channels have a 'voltage-sensing domain' that spans the lipid bilayer. The charged residues in the sensor move in response to the membrane potential changes that open the channel allowing ions movement. There are several types of...
01:26Voltage-gated Ion Channels
Generally, all voltage-gated ion channels have a 'voltage-sensing domain' that spans the lipid bilayer. The charged residues in the sensor move in response to the membrane potential changes that open the channel allowing ions movement. There are several types of...
01:19Membrane Asymmetry Regulating Transporters
Flippase
Eukaryotic flippases are type-IV P-type ATPases or P4-ATPases belonging to P-type ATPase family proteins that are membrane-bound pumps involved in the ATP-mediated transport of ions and molecules across the membrane. Flippases flip specific phospholipids from the outer to the inner leaflet of a membrane. All P4-ATPases have one...
01:12Mechanically-gated Ion Channels
01:12Mechanically-gated Ion Channels