Orai channel C-terminal peptides are key modulators of STIM-Orai coupling and calcium signal generation

Baraniak, James H.; Zhou, Yandong; Nwokonko, Robert M.; Jennette, Michelle R.; Kazzaz, Sarah A.; Stenson, Jazmin M.; Whitsell, Abigale L.; Wang, Youjun; Trebak, Mohamed; Gill, Donald L.

doi:10.1016/j.celrep.2021.109322

Cited by 13 publications

(21 citation statements)

References 61 publications

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“…The coiled-coil motifs were consistently reported to be comparatively stronger in the case of the latter homologs [59]. Considering Orai1, the leucine residues L273 and L276 were identified by to be critical for interactions with STIM1, which was recently confirmed in a study by Baraniak and colleagues (2021) using membrane-anchored but isolated Orai1 C-terminal peptides [59,61].…”

Section: Figurementioning

confidence: 76%

Highlighting the Multifaceted Role of Orai1 N-Terminal- and Loop Regions for Proper CRAC Channel Functions

Humer

Romanin

Höglinger

2022

Cells

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Orai1, the Ca2+-selective pore in the plasma membrane, is one of the key components of the Ca2+release-activated Ca2+ (CRAC) channel complex. Activated by the Ca2+ sensor in the endoplasmic reticulum (ER) membrane, stromal interaction molecule 1 (STIM1), via direct interaction when ER luminal Ca2+ levels recede, Orai1 helps to maintain Ca2+ homeostasis within a cell. It has already been proven that the C-terminus of Orai1 is indispensable for channel activation. However, there is strong evidence that for CRAC channels to function properly and maintain all typical hallmarks, such as selectivity and reversal potential, additional parts of Orai1 are needed. In this review, we focus on these sites apart from the C-terminus; namely, the second loop and N-terminus of Orai1 and on their multifaceted role in the functioning of CRAC channels.

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Section: Figurementioning

confidence: 76%

Highlighting the Multifaceted Role of Orai1 N-Terminal- and Loop Regions for Proper CRAC Channel Functions

Humer

Romanin

Höglinger

2022

Cells

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“…Therefore, hO2 and hO3 are envisioned to have an overall similar structural architecture of the nexus hinge as hO1. Furthermore, mutations of hO2 and hO3 residues corresponding to the earlier mentioned L273 and L276 residues of hO1 also affected the interaction of hO2 and hO3 with STIM1, as well as diminished the I CRAC (Baraniak et al, 2021; Frischauf et al, 2009; Frischauf et al, 2011; Niu et al, 2020). The mechanism how ANSGA causes the constitutive activity of the hO1 channel is also likely different from that of the P245L mutation, since the helicity changes observed in our MD simulations upon ANSGA substitution of LVSHK residues in hO1 remained restricted around the nexus region without affecting the helicity of the TM4 helix region (residues 240-250) encompassing the proline bend caused by P245 ( Figure 5A , Figure 5—figure supplement 1A ).…”

Section: Discussionmentioning

confidence: 90%

“…Zhou et al, 2019). Further, the interactions between plasma membrane targeted C-terminal TM4ext peptides of hO1 or hO3 could not be observed in a recent FRET-based study (Baraniak et al, 2021) which further questions the formation of antiparallel TM4ext interaction pairs between neighboring Orai subunits as reported in the closed dOrai structure (Hou et al, 2012). Future structural studies addressing the closed state of the Orai channel should settle this debate.…”

Section: Introductionmentioning

confidence: 78%

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Dissecting gating mechanisms of Orai calcium channel paralogs using constitutively active Orai mutants that mimic STIM1-gated state

Augustynek

Gyimesi

Dernič

et al. 2021

Preprint

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In humans, there are three paralogs of the Orai Ca2+ channel, which lie at the heart of the store-operated calcium entry (SOCE) machinery. While the STIM-mediated gating mechanism of Orai channels is still being actively investigated, several artificial and natural variants are known to cause constitutive activity of the human Orai1 channel. Surprisingly, little is known about the conservation of the gating mechanism among the different human Orai paralogs and orthologs in other species. In our work, we show that the mutation corresponding to the activating mutation H134A in transmembrane helix 2 (TM2) of human Orai1 also activates Orai2 and Orai3, likely via a similar mechanism. However, this cross-paralog conservation does not apply to the “ANSGA” nexus mutations in TM4 of human Orai1 which mimic the STIM1-activated state of the channel. Investigating the mechanistic background of these differences, we identified two positions, H171 and F246 in human Orai1, which directly control the channel activation triggered by the “ANSGA” mutations in Orai1. Our results shed new light on these important gating checkpoints and show that the gating mechanism of the Orai channels is affected by multiple factors that are not necessarily evolutionarily conserved, such as the TM4-TM3 coupling.

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“…Moreover, in a human MC line, LAD2 cells, shRNA-mediated silencing of STIM-1 results in significant decrease in MRGPRX2-mediated Ca 2+ mobilization and degranulation ( 25 ). Given that STIM-1 couples to Orai1 for Ca 2+ influx ( 26 ), we hypothesized that this CRAC channel contributes to SP-induced responses in human MCs. To test this possibility, we used lentiviral shRNA to individually silence the expression of Orai1, Orai2, and Orai3 in LAD2 cells, which endogenously express MRGPRX2.…”

Section: Resultsmentioning

confidence: 99%

Inhibition of Orai Channel Function Regulates Mas-Related G Protein-Coupled Receptor-Mediated Responses in Mast Cells

et al. 2022

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Mast cells (MCs) are tissue resident immune cells that play important roles in the pathogenesis of allergic disorders. These responses are mediated via the cross-linking of cell surface high affinity IgE receptor (FcϵRI) by antigen resulting in calcium (Ca2+) mobilization, followed by degranulation and release of proinflammatory mediators. In addition to FcϵRI, cutaneous MCs express Mas-related G protein-coupled receptor X2 (MRGPRX2; mouse ortholog MrgprB2). Activation of MRGPRX2/B2 by the neuropeptide substance P (SP) is implicated in neurogenic inflammation, chronic urticaria, mastocytosis and atopic dermatitis. Although Ca2+ entry is required for MRGPRX2/B2-mediated MC responses, the possibility that calcium release-activated calcium (CRAC/Orai) channels participate in these responses has not been tested. Lentiviral shRNA-mediated silencing of Orai1, Orai2 or Orai3 in a human MC line (LAD2 cells) resulted in partial inhibition of SP-induced Ca2+ mobilization, degranulation and cytokine/chemokine generation (TNF-α, IL-8, and CCL-3). Synta66, which blocks homo and hetero-dimerization of Orai channels, caused a more robust inhibition of SP-induced responses than knockdown of individual Orai channels. Synta66 also blocked SP-induced extracellular signal-regulated kinase 1/2 (ERK1/2) and Akt phosphorylation and abrogated cytokine/chemokine production. It also inhibited SP-induced Ca2+ mobilization and degranulation in primary human skin MCs and mouse peritoneal MCs. Furthermore, Synta66 attenuated both SP-induced cutaneous vascular permeability and leukocyte recruitment in mouse peritoneum. These findings demonstrate that Orai channels contribute to MRGPRX2/B2-mediated MC activation and suggest that their inhibition could provide a novel approach for the modulation of SP-induced MC/MRGPRX2-mediated disorders.

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Orai channel C-terminal peptides are key modulators of STIM-Orai coupling and calcium signal generation

Cited by 13 publications

References 61 publications

Highlighting the Multifaceted Role of Orai1 N-Terminal- and Loop Regions for Proper CRAC Channel Functions

Highlighting the Multifaceted Role of Orai1 N-Terminal- and Loop Regions for Proper CRAC Channel Functions

Dissecting gating mechanisms of Orai calcium channel paralogs using constitutively active Orai mutants that mimic STIM1-gated state

Inhibition of Orai Channel Function Regulates Mas-Related G Protein-Coupled Receptor-Mediated Responses in Mast Cells

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