title: Ca(2+)- and volume-sensitive chloride currents are differentially regulated by agonists and store-operated Ca2+ entry.
abstract: Using patch-clamp and calcium imaging techniques, we characterized the effects of ATP and histamine on human keratinocytes. In the HaCaT cell line, both receptor agonists induced a transient elevation of [Ca2+]i in a Ca(2+)-free medium followed by a secondary [Ca2+]i rise upon Ca2+ readmission due to store-operated calcium entry (SOCE). In voltage-clamped cells, agonists activated two kinetically distinct currents, which showed differing voltage dependences and were identified as Ca(2+)-activated (I(Cl(Ca))) and volume-regulated (I(Cl, swell)) chloride currents. NPPB and DIDS more efficiently inhibited I(Cl(Ca)) and I(Cl, swell), respectively. Cell swelling caused by hypotonic solution invariably activated I(Cl, swell) while regulatory volume decrease occurred in intact cells, as was found in flow cytometry experiments. The PLC inhibitor U-73122 blocked both agonist- and cell swelling-induced I(Cl, swell), while its inactive analogue U-73343 had no effect. I(Cl(Ca)) could be activated by cytoplasmic calcium increase due to thapsigargin (TG)-induced SOCE as well as by buffering [Ca2+]i in the pipette solution at 500 nM. In contrast, I(Cl, swell) could be directly activated by 1-oleoyl-2-acetyl-sn-glycerol (OAG), a cell-permeable DAG analogue, but neither by InsP3 infusion nor by the cytoplasmic calcium increase. PKC also had no role in its regulation. Agonists, OAG, and cell swelling induced I(Cl, swell) in a nonadditive manner, suggesting their convergence on a common pathway. I(Cl, swell) and I(Cl(Ca)) showed only a limited overlap (i.e., simultaneous activation), although various maneuvers were able to induce these currents sequentially in the same cell. TG-induced SOCE strongly potentiated I(Cl(Ca)), but abolished I(Cl, swell), thereby providing a clue for this paradox. Thus, we have established for the first time using a keratinocyte model that I(Cl, swell) can be physiologically activated under isotonic conditions by receptors coupled to the phosphoinositide pathway. These results also suggest a novel function for SOCE, which can operate as a "selection" switch between closely localized channels.
authors.affiliation: Laboratoire de Physiologie Cellulaire, INSERM EMI 0228, Université des Sciences et Technologie de Lille, 59655 Villeneuve d'Ascq, France.
authors.forename: Alexander
authors.initials: A
authors.lastname: Zholos
authors.forename: Benjamin
authors.initials: B
authors.lastname: Beck
authors.forename: Vadym
authors.initials: V
authors.lastname: Sydorenko
authors.forename: Loïc
authors.initials: L
authors.lastname: Lemonnier
authors.forename: Pascal
authors.initials: P
authors.lastname: Bordat
authors.forename: Natalia
authors.initials: N
authors.lastname: Prevarskaya
authors.forename: Roman
authors.initials: R
authors.lastname: Skryma
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology*; D002118:Calcium / Q000493:pharmacokinetics*; D002460:Cell Line; D048429:Cell Size; D018118:Chloride Channels / Q000502:physiology*; D004594:Electrophysiology; D005434:Flow Cytometry; D006632:Histamine / Q000494:pharmacology*; D006801:Humans; D015603:Keratinocytes; D018408:Patch-Clamp Techniques; D018160:Receptors, Cytoplasmic and Nuclear / Q000502:physiology; D011968:Receptors, Histamine / Q000502:physiology
chemical_list: D018118:Chloride Channels; D018160:Receptors, Cytoplasmic and Nuclear; D011968:Receptors, Histamine; C040985:phosphatidylinositol receptors; D006632:Histamine; D000255:Adenosine Triphosphate; D002118:Calcium