Store-dependent and -independent modes regulating CRAC channel activity of human Orai1 and Orai3

Authors:
Zhang SL, Kozak JA, Jiang W, Yeromin AV, Chen J, Yu Y, Penna A, Shen W, Chi V, Cahalan MD
In:
Source: J Biol Chem
Publication Date: (2008)
Issue: 283(25): 17662-71
Research Area:
Cancer Research/Cell Biology
Cells used in publication:
293
Species: human
Tissue Origin: kidney
Jurkat
Species: human
Tissue Origin: blood
Platform:
Nucleofectorâ„¢ I/II/2b
Abstract
We evaluated currents induced by expression of human homologs of Orai together with STIM1 in HEK cells. When coexpressed with STIM1, Orai1 induced a large inwardly rectifying Ca2+ selective current with Ca2+-induced slow inactivation. A point mutation of Orai1 (E106D) altered the ion selectivity of the induced CRAC-like current while retaining an inwardly rectifying I-V characteristic. Expression of the C-terminal portion of STIM1 with Orai1 was sufficient to generate CRAC current without store depletion. 2-APB activated a large relatively nonselective current in STIM1 and Orai3 co-expressing cells. 2-APB also induced Ca2+ influx in Orai3-expressing cells without store depletion or co-expression of STIM1. The Orai3 current induced by 2-APB exhibited outward rectification and an inward component representing a mixed calcium- and monovalent current. A pore mutant of Orai3 inhibited store-operated Ca2+ entry and did not carry significant current in response to either store depletion or addition of 2-APB. Analysis of a series of Orai1-3 chimeras revealed the structural determinant responsible for 2-APB-induced current within the sequence from the second to third transmembrane segment of Orai3. The Orai3 current induced by 2-APB may reflect a store-independent mode of CRAC channel activation that opens a relatively nonselective cation pore.