title: Expression and biological significance of Ca2+-activated ion channels in human keratinocytes.
abstract: In whole-cell recordings from HaCaT keratinocytes, ATP, bradykinin, and histamine caused a biphasic change of the membrane potential consisting of an initial transient depolarization, followed by a pronounced and long-lasting hyperpolarization. Flash photolysis of caged IP3 mimicked the agonist-induced voltage response, suggesting that intracellular Ca2+ release and subsequent opening of Ca2+-activated ion channels serve as the common transduction mechanism. In contrast, cAMP- and PKC-dependent pathways were not involved in the electrophysiological effects of the extracellular signaling molecules. The depolarization was predominantly mediated by a DIDS- and niflumic acid-sensitive Cl- current, whereas a charybdotoxin- and clotrimazole-sensitive K+ current underlay the prominent hyperpolarization. Consistent with the electrophysiological data, RT-PCR showed that HaCaT keratinocytes express two types of Ca2+-activated Cl- channels, CaCC2 and CaCC3 (CLCA2), as well as the Ca2+-activated K+ channel hSK4. That the pronounced hSK4-mediated hyperpolarization bears significance on the growth and differentiation properties of keratinocytes is suggested by RNase protection assays showing that hSK4 mRNA expression is strongly down-regulated under conditions that allow keratinocyte differentiation. hSK4 might thus play a role in linking changes in membrane potential to the biological fate of keratinocytes.
authors.affiliation: Department of Physiology, University of Munich, D-80336 Munich, Germany.
authors.forename: H
authors.initials: H
authors.lastname: Koegel
authors.forename: C
authors.initials: C
authors.lastname: Alzheimer
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000494:pharmacology; D001562:Benzimidazoles / Q000494:pharmacology; D001920:Bradykinin / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology*; D002120:Calcium Channel Agonists / Q000494:pharmacology; D002412:Cations / Q000378:metabolism; D002460:Cell Line; D018999:Charybdotoxin / Q000494:pharmacology; D018118:Chloride Channels / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D002712:Chlorides / Q000378:metabolism; D003022:Clotrimazole / Q000494:pharmacology; D004553:Electric Conductivity; D006632:Histamine / Q000494:pharmacology; D006801:Humans; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D015640:Ion Channel Gating / Q000187:drug effects*; D015603:Keratinocytes / Q000187:drug effects* / Q000378:metabolism; D008536:Meglumine / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D009544:Niflumic Acid / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D010782:Photolysis; D011188:Potassium / Q000378:metabolism; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism
chemical_list: D001562:Benzimidazoles; D002120:Calcium Channel Agonists; D002412:Cations; D018118:Chloride Channels; D002712:Chlorides; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D012333:RNA, Messenger; D018999:Charybdotoxin; D009544:Niflumic Acid; D008536:Meglumine; D006632:Histamine; D015544:Inositol 1,4,5-Trisphosphate; D000255:Adenosine Triphosphate; D003022:Clotrimazole; C102635:1-ethyl-2-benzimidazolinone; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D011188:Potassium; D001920:Bradykinin; D002118:Calcium