Modulation of Ca2+ entry and plasma membrane potential by human TRPM4b
Ralf Fliegert1, Günter Glassmeier, Frederike Schmid
1Calcium Signalling Group, Institute of Biochemistry and Molecular Biology I: Cellular Signal Transduction, Center of Experimental Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
The FEBS Journal
|February 10, 2007
Summary
Transient Receptor Potential Melastatin 4b (TRPM4b) channels regulate calcium (Ca2+) influx. In HEK-293 cells, TRPM4b acts as a positive regulator, enhancing sustained Ca2+ entry by facilitating repolarization.
Area of Science:
- Molecular Biology
- Cell Physiology
- Ion Channel Function
Background:
- Transient Receptor Potential Melastatin 4b (TRPM4b) is a calcium-activated, voltage-dependent monovalent cation channel.
- TRPM4b has been implicated as a negative regulator of calcium (Ca2+) entry and in Ca2+ influx oscillations in Jurkat T-lymphocytes.
Purpose of the Study:
- To investigate the role and localization of TRPM4b in human embryonic kidney (HEK) cells.
- To determine the functional impact of TRPM4b overexpression on calcium influx and membrane potential dynamics.
Main Methods:
- Transient and stable overexpression of TRPM4b in HEK-293 cells.
- Confocal fluorescence microscopy for plasma membrane localization.
- Whole-cell and perforated patch-clamp electrophysiology to record ion currents and membrane potential.
- Measurement of Ca2+ influx using ionomycin stimulation and potentiometric dyes.
Main Results:
- Overexpressed TRPM4b localized to the plasma membrane and exhibited Ca2+-dependent currents.
- HEK-293 cells overexpressing TRPM4b showed increased ionomycin-activated Ca2+ influx.
- TRPM4b expression accelerated initial depolarization and facilitated repolarization, enhancing sustained Ca2+ influx.
Conclusions:
- In HEK-293 cells, TRPM4b functions as a positive regulator of Ca2+ entry.
- TRPM4b enhances sustained Ca2+ influx by modulating membrane potential dynamics.
Related Concept Videos
01:16Calmodulin-dependent Signaling
Calmodulin (CaM) is a calcium-binding protein in eukaryotes that controls various calcium-regulated cellular processes. It has four calcium-binding sites that bind calcium to form the calcium-calmodulin ( Ca2+-CaM) complex. GPCR stimulation increases the calcium levels in the cells that bind to CaM and induces a conformational change.
The Ca2+-CaM complex does not have enzymatic activity by itself. Instead, the complex binds downstream target proteins, including membrane proteins or enzymes,...
The Ca2+-CaM complex does not have enzymatic activity by itself. Instead, the complex binds downstream target proteins, including membrane proteins or enzymes,...
01:27Feedback Regulation of Calcium Concentration
Calcium is an essential signaling molecule required for various cellular functions. Calcium pumps and ion channels on cell and organellar membranes, such as those on the endoplasmic reticulum (ER), regulate calcium concentrations inside the cell. They remain closed, keeping the cytosolic calcium levels low at a resting state.
Various transmembrane receptors, such as G protein-coupled receptors (GPCRs), elicit a response to extracellular signals by increasing cytosolic calcium. Activated GPCRs...
Various transmembrane receptors, such as G protein-coupled receptors (GPCRs), elicit a response to extracellular signals by increasing cytosolic calcium. Activated GPCRs...
01:12Mechanically-gated Ion Channels
Mechanically-gated ion channels are proteins found in eukaryotic and prokaryotic cell membranes that open in response to mechanical stress. Tension, compression, swelling, and shear stress can alter the conformation of the protein, opening a transmembrane channel that allows the passage of ions for signal transmission. In eukaryotes, mechanically-gated channels are distributed in several regions like the neurons, lungs, skin, bladder, and heart, where they play critical roles in numerous...
01:43Thermosensation
Peripheral thermosensation is the perception of external temperature. A change in temperature (on the surface of the skin and other tissues) is detected by a family of temperature-sensitive ion channels called Transient Receptor Potential, or TRP, receptors. These receptors are located on free nerve endings. Those detecting cold temperatures are closer to the surface of the skin than the nerve endings detecting warmth. These thermoTRP channels, while temperature selective, have relatively...
01:11IP3/DAG Signaling Pathway
Membrane lipids such as phosphatidylinositol (PI) are precursors for several membrane-bound and soluble second messengers. Specific kinases phosphorylate PI and produce phosphorylated inositol phospholipids. One such inositol phospholipids are the phosphatidylinositol-4,5 bisphosphate [PI(4,5)P2], present in the inner half of the lipid bilayer. Upon ligand binding, GPCR stimulates Gq proteins to turn on phospholipase Cꞵ. Activated phospholipase Cꞵ cleaves PI(4,5)P2 and produces two-second...
01:30Ligand-Gated Ion Channel Receptor: Gating Mechanism
Ligand-gated ion channels are transmembrane proteins that play a vital role in intercellular communication and functions of the nervous system. They allow the influx of ions across the membrane once the neurotransmitter binds, allowing the subsequent transmission of electrical excitation across the neurons. Other ligand-gated ion channels, like the γ-aminobutyric acid (GABA) receptor, permit anions like chloride into the cells on the binding of the GABA molecule. Their entry into the cell...