  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
