Complex Actions of 2-Aminoethyldiphenyl Borate on Store-operated Calcium Entry

Store-operated Ca2+ entry (SOCE) is likely the most common mode of regulated influx of Ca2+ into cells. However, only a limited number of pharmacological agents have been shown to modulate this process. 2-Aminoethyldiphenyl borate (2-APB) is a widely used experimental tool that activates and then in...

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Bibliographic Details
Published in:The Journal of biological chemistry 2008-07, Vol.283 (28), p.19265-19273
Main Authors: DeHaven, Wayne I., Smyth, Jeremy T., Boyles, Rebecca R., Bird, Gary S., Putney, James W.
Format: Article
Language:English
Subjects:
Boron Compounds - pharmacology
Calcium - metabolism
Calcium Channel Agonists - pharmacology
Calcium Channels - genetics
Calcium Channels - metabolism
Cell Line
Humans
Membrane Potentials - drug effects
Membrane Proteins - genetics
Membrane Proteins - metabolism
Neoplasm Proteins - genetics
Neoplasm Proteins - metabolism
ORAI1 Protein
ORAI2 Protein
Stromal Interaction Molecule 1
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Summary:Store-operated Ca2+ entry (SOCE) is likely the most common mode of regulated influx of Ca2+ into cells. However, only a limited number of pharmacological agents have been shown to modulate this process. 2-Aminoethyldiphenyl borate (2-APB) is a widely used experimental tool that activates and then inhibits SOCE and the underlying calcium release-activated Ca2+ current (ICRAC). The mechanism by which depleted stores activates SOCE involves complex cellular movements of an endoplasmic reticulum Ca2+ sensor, STIM1, which redistributes to puncta near the plasma membrane and, in some manner, activates plasma membrane channels comprising Orai1, -2, and -3 subunits. We show here that 2-APB blocks puncta formation of fluorescently tagged STIM1 in HEK293 cells. Accordingly, 2-APB also inhibited SOCE and ICRAC-like currents in cells co-expressing STIM1 with the CRAC channel subunit, Orai1, with similar potency. However, 2-APB inhibited STIM1 puncta formation less well in cells co-expressing Orai1, indicating that the inhibitory effects of 2-APB are not solely dependent upon STIM1 reversal. Further, 2-APB only partially inhibited SOCE and current in cells co-expressing STIM1 and Orai2 and activated sustained currents in HEK293 cells expressing Orai3 and STIM1. Interestingly, the Orai3-dependent currents activated by 2-APB showed large outward currents at potentials greater than +50 mV. Finally, Orai3, and to a lesser extent Orai1, could be directly activated by 2-APB, independently of internal Ca2+ stores and STIM1. These data reveal novel and complex actions of 2-APB effects on SOCE that can be attributed to effects on both STIM1 as well as Orai channel subunits.
ISSN:0021-9258
1083-351X
DOI:10.1074/jbc.M801535200