Spontaneous single-channel activity of neuronal TRP5 channel recombinantlyexpressed in HEK293 cells

Mammalian homologues of the Drosophila transient receptor potential (trp) p rotein (TRP) form Ca2+ permeable cation channels activated in response to s timulation of G-protein-coupled receptors. Establishing biophysical charact eristics of basal TRP activity is of great importance in understanding modu latory processes, which underlie enhancement of TRP activity via receptor s timulation. We have examined spontaneous activity of the TRP5 channel recom binantly expressed in human embryonic kidney cells, using the conventional whole-cell mode of the patch-damp technique in a low-Ca2+ external solution . The unitary Na+ conductance of the TRP5 channel was linear, being 47.6 pS . By contrast, the open probability of the TRP5 channel showed a voltage-de pendent decrease below -50 mV. These biophysical properties are important h allmarks in distinguishing the TRP5 channel in native neuronal preparations , whose spontaneous activity may contribute to control of resting membrane potentials and generation of action potentials. (C) 2000 Elsevier Science i reland Ltd. All rights reserved.