Calcium-activated K(+) channel (K(Ca)3.1) activity during Ca(2+) store depletion and store-operated Ca(2+) entry in human macrophages.
STIM1 'senses' decreases in endoplasmic reticular (ER) luminal Ca(2+) and induces store-operated Ca(2+) (SOC) entry through plasma membrane Orai channels. The Ca(2+)/calmodulin-activated K(+) channel K(Ca)3.1 (previously known as SK4) has been implicated as an 'amplifier' of the Ca(2+)-release activated Ca(2+) (CRAC) current, especially in T lymphocytes. We have previously shown that human macrophages express K(Ca)3.1, and here we used the whole-cell patch-clamp technique to investigate the activity of these channels during Ca(2+) store depletion and store-operated Ca(2+) influx. Using RT-PCR, we found that macrophages express the elementary CRAC channel components Orai1 and STIM1, as well as Orai2, Orai3 and STIM2, but not the putatively STIM1-activated channels TRPC1, TRPC3-7 or TRPV6. In whole-cell configuration, a robust Ca(2+)-induced outwardly rectifying K(+) current inhibited by clotrimazole and augmented by DC-EBIO could be detected, consistent with K(Ca)3.1 channel current (also known as intermediate-conductance IK1). Introduction of extracellular Ca(2+) following Ca(2+) store depletion via P2Y(2) receptors induced a robust charybdotoxin (CTX)- and 2-APB-sensitive outward K(+) current and hyperpolarization. We also found that SOC entry induced by thapsigargin treatment induced CTX-sensitive K(+) current in HEK293 cells transiently expressing K(Ca)3.1. Our data suggest that SOC and K(Ca)3.1 channels are tightly coupled, such that a small Ca(2+) influx current induces a much large K(Ca)3.1 channel current and hyperpolarization, providing the necessary electrochemical driving force for prolonged Ca(2+) signaling and store repletion.
Gao
Ya-dong
YD
Institut für Physiologie und Pathophysiologie, Universität Marburg, Deutschhausstr. 2, 35037 Marburg, Germany. gaoyadong@hotmail.com
Hanley
Peter J
PJ
Rinné
Susanne
S
Zuzarte
Marylou
M
Daut
Jurgen
J
D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000096:biosynthesis*; D020013:Calcium Signaling / Q000502:physiology*; D015815:Cell Adhesion Molecules / Q000096:biosynthesis; D018999:Charybdotoxin / Q000494:pharmacology; D003022:Clotrimazole / Q000494:pharmacology; D057809:HEK293 Cells; D006801:Humans; D051660:Intermediate-Conductance Calcium-Activated Potassium Channels / Q000378:metabolism / Q000502:physiology*; D008264:Macrophages / Q000378:metabolism*; D008565:Membrane Proteins / Q000096:biosynthesis*; D009363:Neoplasm Proteins / Q000096:biosynthesis*; D000071740:ORAI1 Protein; D000071741:ORAI2 Protein; D018408:Patch-Clamp Techniques; D000071737:Stromal Interaction Molecule 1; D000071738:Stromal Interaction Molecule 2; D014544:Uridine Triphosphate / Q000494:pharmacology
D015220:Calcium Channels; D015815:Cell Adhesion Molecules; D051660:Intermediate-Conductance Calcium-Activated Potassium Channels; C496923:KCNN4 protein, human; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D000071740:ORAI1 Protein; C510746:ORAI1 protein, human; D000071741:ORAI2 Protein; C514506:ORAI2 protein, human; C522867:Orai3 protein, human; C103530:STIM1 protein, human; C513279:STIM2 protein, human; D000071737:Stromal Interaction Molecule 1; D000071738:Stromal Interaction Molecule 2; D018999:Charybdotoxin; D003022:Clotrimazole; D002118:Calcium; D014544:Uridine Triphosphate