Comparing ion conductance recordings of synthetic lipid bilayers with cell membranes containing TRP channels.
In this article we compare electrical conductance events from single channel recordings of three TRP channel proteins (TRPA1, TRPM2 and TRPM8) expressed in human embryonic kidney cells with channel events recorded on synthetic lipid membranes close to melting transitions. Ion channels from the TRP family are involved in a variety of sensory processes including thermo- and mechano-reception. Synthetic lipid membranes close to phase transitions display channel-like events that respond to stimuli related to changes in intensive thermodynamic variables such as pressure and temperature. TRP channel activity is characterized by typical patterns of current events dependent on the type of protein expressed. Synthetic lipid bilayers show a wide spectrum of electrical phenomena that are considered typical for the activity of protein ion channels. We find unitary currents, burst behavior, flickering, multistep-conductances, and spikes behavior in both preparations. Moreover, we report conductances and lifetimes for lipid channels as described for protein channels. Non-linear and asymmetric current-voltage relationships are seen in both systems. Without further knowledge of the recording conditions, no easy decision can be made whether short current traces originate from a channel protein or from a pure lipid membrane.
Membrane Biophysics Group, Niels Bohr Institute, University of Copenhagen, Denmark.
Katrine R
KR
Laub
Katja
K
Witschas
Andreas
A
Blicher
Søren B
SB
Madsen
Andreas
A
Lückhoff
Thomas
T
Heimburg
D015220:Calcium Channels / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D002462:Cell Membrane / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D017136:Ion Transport / Q000502:physiology; D008051:Lipid Bilayers / Q000737:chemistry* / Q000378:metabolism; D008564:Membrane Potentials / Q000502:physiology; D009419:Nerve Tissue Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D000074025:TRPA1 Cation Channel; D050053:TRPM Cation Channels / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D050051:Transient Receptor Potential Channels / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
D015220:Calcium Channels; D008051:Lipid Bilayers; D009419:Nerve Tissue Proteins; D000074025:TRPA1 Cation Channel; C473350:TRPA1 protein, human; D050053:TRPM Cation Channels; C121934:TRPM2 protein, human; C425966:TRPM8 protein, human; D050051:Transient Receptor Potential Channels