The store-operated calcium entry pathways in human carcinoma A431 cells: functional properties and activation mechanisms.
Activation of phospholipase C (PLC)-mediated signaling pathways in nonexcitable cells causes the release of Ca2+ from intracellular Ca2+ stores and activation of Ca2+ influx across the plasma membrane. Two types of Ca2+ channels, highly Ca2+-selective ICRAC and moderately Ca2+-selective ISOC, support store-operated Ca2+ entry process. In previous patch-clamp experiments with a human carcinoma A431 cell line we described store-operated Imin/ICRACL plasma membrane Ca2+ influx channels. In the present paper we use whole-cell and single-channel recordings to further characterize store-operated Ca2+ influx pathways in A431 cells. We discovered that (a) ICRAC and ISOC are present in A431 cells; (b) ICRAC currents are highly selective for divalent cations and fully activate within 150 s after initiation of Ca2+ store depletion; (c) ISOC currents are moderately selective for divalent cations (PBa/PCs = 14.5) and require at least 300 s for full activation; (d) ICRAC and ISOC currents are activated by PLC-coupled receptor agonists; (e) ISOC currents are supported by Imin/ICRACL channels that display 8.5-10 pS conductance for sodium; (f) ICRAC single channel conductance for sodium is estimated at 0.9 pS by the noise analysis; (g) Imin/ICRACL channels are activated in excised patches by an amino-terminal fragment of InsP3R1 (InsP3R1N); and (h) InsP3 binding to InsP3R1N is necessary for activation of Imin/ICRACL channels. Our findings provide novel information about store-operated Ca2+ influx pathways in A431 cells.
Gusev
Konstantin
K
Department of Physiology, K4.112, UT Southwestern Medical Center at Dallas, 5323 Harry Hines Blvd., Dallas, TX 75390-9040, USA.
Glouchankova
Lyuba
L
Zubov
Alexander
A
Kaznacheyeva
Elena
E
Wang
Zhengnan
Z
Bezprozvanny
Ilya
I
Mozhayeva
Galina N
GN
D015220:Calcium Channels / Q000145:classification / Q000502:physiology*; D020013:Calcium Signaling / Q000502:physiology*; D002277:Carcinoma / Q000378:metabolism; D006801:Humans; D007424:Intracellular Fluid / Q000378:metabolism; D015640:Ion Channel Gating / Q000502:physiology*; D008564:Membrane Potentials / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology*; D014407:Tumor Cells, Cultured; D010738:Type C Phospholipases / Q000378:metabolism
D015220:Calcium Channels; D010738:Type C Phospholipases