Voltage Gating at the Selectivity Filter of the Ca2+ Release-activated Ca2+ Channel Induced by Mutation of the Orai1 Protein

Spassova, Maria A.; Hewavitharana, Thamara; Fandino, Richard A.; Kaya, Asli; Tanaka, Jacqueline C.; Gill, Donald L.

doi:10.1074/jbc.m702208200

Cited by 17 publications

(17 citation statements)

References 41 publications

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“…The protein chemistry complements electrophysiological evidence that ORAI1(E106D) channels have lower affinity for Ca 2þ than wild-type channels, as measured by the ability of Ca 2þ to block monovalent ion currents (6,32), and strengthens the conclusion that E106 carboxyl groups form a binding site or binding sites for Ca 2þ . This conclusion is further supported by the findings that ORAI1(E106A) channels do not conduct Ca 2þ (6,33) and that a single E106Q substitution in a concatenated ORAI1 tetramer prevents Ca 2þ current through the channel (27).…”

Section: Discussionmentioning

confidence: 62%

“…The rigidity or close packing of the segment containing residues 99-104 may serve to hold E106 carboxyl groups in position to coordinate Ca 2þ . The voltage dependence conferred by the V102I substitution (33) demonstrates that the channel is exquisitely sensitive to the packing of side chains in this segment of TM1. The central location of TM1 in the ORAI1 channel ensures that Ca 2þ or other ions leaving the E106 site and passing inward through the channel, whatever their detailed path, will confront a part of the channel lined at least in part by nonpolar side chains projecting from the helical turns of TM1 immediately internal to E106.…”

Section: Discussionmentioning

confidence: 99%

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Pore architecture of the ORAI1 store-operated calcium channel

Zhou

Ramachandran

Oh‐hora

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

135

176

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ORAI1 is the pore-forming subunit of the calcium release-activated calcium (CRAC) channel, a store-operated channel that is central to Ca 2þ signaling in mammalian cells. Electrophysiological data have shown that the acidic residues E106 in transmembrane helix 1 (TM1) and E190 in TM3 contribute to the high selectivity of ORAI1 channels for Ca 2þ . We have examined the pore architecture of the ORAI1 channel using ORAI1 proteins engineered to contain either one or two cysteine residues. Disulfide cross-linking shows that ORAI1 assembles as a tetramer or a higher oligomer with TM1 centrally located. Cysteine side chains projecting from TM1 at position 88, 95, 102, or 106 cross-link efficiently to the corresponding side chain in a second ORAI1 monomer. Cysteine residues at position 190 or at surrounding positions in TM3 do not cross-link. We conclude that E106 residues in wild-type ORAI1 are positioned to form a Ca 2þ binding site in the channel pore and that E190 interacts less directly with ions traversing the pore. The cross-linking data further identify a relatively rigid segment of TM1 adjacent to E106 that is likely to contribute to the selectivity filter.cross-linking | membrane protein | store-operated calcium entry | stromal interaction molecule | structure T he electrophysiologically defined calcium release-activated calcium (CRAC) channel is responsible for physiological Ca 2þ influx in T cells and mast cells and for store-operated Ca 2þ entry in other cells (1). CRAC currents in human T cells require the protein ORAI1 (2-4), which has been shown to be a plasma membrane Ca 2þ channel protein [(5-8); reviewed in refs. 9-11]. The severe combined immunodeficiencies that result from rare mutations in the human ORAI1 gene and the functional deficits of Orai1 −∕− mice dramatize the crucial signaling role played by ORAI1 in Tcells and mast cells (2,(12)(13)(14). The hallmarks of native CRAC channels and of recombinant ORAI1 channels are that they open in response to a reduction of Ca 2þ concentration in the endoplasmic reticulum (ER) lumen, that they are highly selective for Ca 2þ under physiological conditions, and that they carry only very small single-channel currents (1, 11). The sensitivity of the channel to the level of ER Ca 2þ stores has been traced to the ER-resident Ca 2þ sensor protein STIM1 (15)(16)(17)(18)(19)(20), but the basis for other channel properties is not understood in any detail.Point mutations introduced into the transmembrane helices of ORAI1 or its Drosophila orthologue alter ion selectivity (5-7). The replacements E106D or E190Q in human ORAI1 sharply reduce the ability of the channel to discriminate between Ca 2þ and Na þ under physiological conditions and reduce the decided preference of the channel for Na þ over Cs þ under conditions where the channel conducts monovalent ions (6, 7). However, although the electrophysiological analysis shows that E106 and E190 influence ion movements within the channel pore, it does not establish whether these residues do so directly by coordinating ...

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Section: Discussionmentioning

confidence: 62%

Section: Discussionmentioning

confidence: 99%

Pore architecture of the ORAI1 store-operated calcium channel

Zhou

Ramachandran

Oh‐hora

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

135

176

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“…68 Pore mutants that modify Orai1 channel voltage sensitivity include point mutation V102I as well as V105I close to the selectivity filter. 72 In conclusion these studies reveal that structural elements contributing to ion permeation are located close to those involved in the voltage gating of Orai1 channels.…”

Section: Store-operated Activation Of Stim/oraimentioning

confidence: 70%

The STIM/Orai coupling machinery

Frischauf¹,

Schindl²,

Derler³

et al. 2008

Channels

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“…Hence, additional regions besides coiled-coil domains may contribute, and/or a third component somewhat stabilizing the STIM1-Orai1 coupling complex might be involved (46,47). The coiled-coil domains in the STIM1 C terminus have been suggested as important domains affecting Orai1 activation (14,33,43,48) and are included within the recently identified key fragments CAD or SOAR. Coiled-coil deletion mutants of STIM1 display pronounced tubular vesicular shape arrangement in comparison with wild-type STIM1, do not form puncta following store depletion, and fail to activate Orai1-derived Ca 2ϩ -influx (14).…”

Section: Discussionmentioning

confidence: 99%

Molecular Determinants of the Coupling between STIM1 and Orai Channels

Frischauf

Muik

Derler

et al. 2009

Journal of Biological Chemistry

141

102

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STIM1 and Orai1 have been reported to interact upon store depletion culminating in Ca2؉ release-activated Ca 2؉ current activation. Recently, the essential region has been identified within the STIM1 C terminus that includes the second coiledcoil domain C-terminally extended by ϳ50 amino acids and exhibits a strong binding to the Orai1 C terminus. Based on the homology within the Orai family, an analogous scenario might be assumed for Orai2 as well as Orai3 channels as both are activated in a similar STIM1-dependent manner. A combined approach of electrophysiology and Foerster resonance energy transfer microscopy uncovered a general mechanism in the communication of STIM1 with Orai proteins that involved the conserved putative coiled-coil domains in the respective Orai C terminus and the second coiled-coil motif in the STIM1 C terminus. A coiled-coil single mutation in the Orai1 C terminus abrogated communication with the STIM1 C terminus, whereas an analogous mutation in Orai2 and Orai3 still allowed for their moderate activation. However, increasing coiled-coil probability by a gain of function deletion in Orai1 or by generating an Orai1-Orai3 chimera containing the Orai3 C terminus recovered stimulation to a similar extent as with Orai2/3. At the level of STIM1, decreasing probability of the second coiled-coil domain by a single mutation within the STIM1 C terminus abolished activation of Orai1 but still enabled partial stimulation of Orai2/3 channels. A double mutation within the second coiled-coil motif of the STIM1 C terminus fully disrupted communication with all three Orai channels. In aggregate, the impairment in the overall communication between STIM1 and Orai channels upon decreasing probabilities of either one of the putative coiled-coil domains in the C termini might be compatible with the concept of their functional, heteromeric interaction.Store-operated Ca 2ϩ entry is a key to cellular regulation of short term responses such as contraction and secretion as well as long term processes like proliferation and cell growth (1). The prototypic and best characterized store-operated channel is the Ca 2ϩ release-activated Ca 2ϩ (CRAC) 5 channel (2-6). However, its molecular components have remained elusive until 4 years ago; the STIM1 (stromal interacting molecule 1) (7,8) and later on Orai1 (9 -11) have been identified as the two limiting components for CRAC activation. STIM1 is an ERlocated Ca 2ϩ sensor, and store depletion triggers its aggregation into punctae close to the plasma membrane, resulting in stimulation of CRAC currents (12,13). Its N terminus is located in the ER lumen and contains an EF-hand Ca 2ϩ -binding motif, which senses the ER Ca 2ϩ level, and a sterile ␣-motif, which is suggested to mediate homomeric STIM1 aggregation (14 -16). In the cytosolic STIM1 C terminus, two coiled-coil regions overlapping with the ezrin-radixin-moesin-like domain and a lysine-rich region are essential for CRAC activation (14,17,18). Three recent studies have independently identified the ezrinradixin-moesin ...

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Voltage Gating at the Selectivity Filter of the Ca2+ Release-activated Ca2+ Channel Induced by Mutation of the Orai1 Protein

Cited by 17 publications

References 41 publications

Pore architecture of the ORAI1 store-operated calcium channel

Pore architecture of the ORAI1 store-operated calcium channel

The STIM/Orai coupling machinery

Molecular Determinants of the Coupling between STIM1 and Orai Channels

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