Plasma membrane insertion of TRPC5 channels contributes to the cholinergic plateau potential in hippocampal CA1 pyramidal neurons.
In cultured hippocampal neurons, transient receptor potential 5 (TRPC5) channels are translocated and inserted into plasma membranes of hippocampal neurons to generate nonselective cation (NSC) currents. We investigated whether TRPC5 channel translocation also contributes to the generation of NSC currents underlying the afterdepolarizations and plateau potentials (PPs) in hippocampal pyramidal cells that are induced by muscarinic receptor activation. Using a biotinylation assay to quantify the change in surface membrane proteins in acute hippocampal slices, we found that muscarinic stimulation significantly enhanced the levels of TRPC5 protein on the membrane surface but not those of TRPC1 or TRPC4 channels. We then investigated the pharmacological sensitivity of the cation current observed during muscarinic stimulation to determine if a component could be due to TRPC5 channels. The TRPC channel antagonists 2-APB and SKF96365 strongly depressed the generation of PPs, the underlying tail currents (I(tail)) and the associated dendritic Ca(2+) influx induced by muscarinic receptor activation in pyramidal neurons. High intracellular concentrations of ATP, which specifically inhibit TRPC5 channels, depressed I(tail). In addition, pretreatment with the calmodulin (CaM) inhibitor W-7, which depresses recombinant TRPC5 currents, inhibited both the cation current (I(tail)) and the surface insertion of TRPC5 channels. Finally, the phosphatidylinositide 3-kinase (PI(3)K) inhibitor wortmannin, which blocks translocation of TRPC5 channels in cell culture, also inhibited both the I(tail) and the surface insertion of TRPC5 channels. Therefore, we conclude that insertion of TRPC5 channels contributes to the generation of the prolonged afterdepolarizations following muscarinic stimulation. This altered plasma membrane expression of TRPC5 channels in pyramidal neurons may play an important role in the generation of prolonged neuronal depolarization and bursting during the epileptiform seizure discharges of epilepsy.
Tai
Chao
C
Brain Research Centre, Department of Psychiatry, University of British Columbia, 2211 Wesbrook Mall, Vancouver, British Columbia, Canada V6T 2B5.
Hines
Dustin J
DJ
Choi
Hyun B
HB
MacVicar
Brian A
BA
D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D001896:Boron Compounds / Q000494:pharmacology; D056547:CA1 Region, Hippocampal / Q000378:metabolism*; D020013:Calcium Signaling; D002147:Calmodulin / Q000037:antagonists & inhibitors; D002462:Cell Membrane / Q000378:metabolism*; D003712:Dendrites / Q000378:metabolism; D004827:Epilepsy / Q000503:physiopathology / Q000628:therapy; D006801:Humans; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology*; D008856:Microscopy, Fluorescence; D018408:Patch-Clamp Techniques; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017785:Photons; D017966:Pyramidal Cells / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011976:Receptors, Muscarinic / Q000378:metabolism*; D013449:Sulfonamides / Q000494:pharmacology; D050052:TRPC Cation Channels / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000077191:Wortmannin
D000730:Androstadienes; D001896:Boron Compounds; D002147:Calmodulin; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011976:Receptors, Muscarinic; D013449:Sulfonamides; D050052:TRPC Cation Channels; C489571:TRPC4 ion channel; C503500:Trpc5 protein, rat; C096351:transient receptor potential cation channel, subfamily C, member 1; C017967:W 7; C109986:2-aminoethoxydiphenyl borate; D000077191:Wortmannin