Menthol increases human glioblastoma intracellular Ca2+, BK channel activity and cell migration.
This study examined the effect of menthol, an agonist for transient receptor potential melastatin 8 (TRPM8) ion channels, to increase intracellular Ca2+ concentration, [Ca2+]i, in human glioblastoma cells (DBTRG cells), which resulted in activation of the large-conductance Ca2+-activated K+ membrane ion channels (BK channels). Voltage ramps applied over 300 ms from -100 to 100 mV resulted in membrane currents with marked inwardly- and outwardly-rectifying components. Paxilline (2 microM) abolished the outwardly-rectifying current. Outwardly-rectifying on-cell patch currents were increased markedly by menthol (100 microM) added to the bath. The estimated on-cell conductance of these channels was 253 pS. Kinetic analysis showed that added menthol increased channel open probability and mean open frequency after 5 min. In a similar time course menthol increased [Ca2+]i, and this increase was abolished either by added paxilline, tetraethylammonium ion or by Ca2+-free external solution. Finally, menthol stimulated the rate of DBTRG cell migration into scratch wounds made in confluent cells, and this also was inhibited by paxilline or by tetraethylammonium ion. We conclude that menthol, a TRPM8 agonist, increases DBTRG cell [Ca2+]i that in turn activates membrane BK ion channels. Inhibition of BK channels by paxilline reverses menthol-stimulated increase of [Ca2+]i and of cell migration. Thus, BK channels function to maintain elevations in [Ca2+]i needed to sustain increases in DBTRG cell migration.
Wondergem
Robert
R
Department of Physiology, James H Quillen College of Medicine, East Tennessee State University, PO Box 70,576, Johnson City, Tennessee 37614-1708, USA. wonderge@etsu.edu
Bartley
Jeremy W
JW
D001932:Brain Neoplasms / Q000378:metabolism / Q000473:pathology*; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects* / Q000502:physiology; D045744:Cell Line, Tumor / Q000187:drug effects / Q000378:metabolism; D002465:Cell Movement / Q000187:drug effects; D005909:Glioblastoma / Q000378:metabolism / Q000473:pathology*; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D017136:Ion Transport / Q000187:drug effects; D051036:Large-Conductance Calcium-Activated Potassium Channels / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D008610:Menthol / Q000494:pharmacology*; D009361:Neoplasm Invasiveness; D018408:Patch-Clamp Techniques; D050053:TRPM Cation Channels / Q000037:antagonists & inhibitors
D007211:Indoles; D051036:Large-Conductance Calcium-Activated Potassium Channels; D050053:TRPM Cation Channels; C425966:TRPM8 protein, human; D008610:Menthol; C048220:paxilline; D002118:Calcium