KRAP tethers IP3 receptors to actin and licenses them to evoke cytosolic Ca2+ signals

Thillaiappan, Nagendra Babu; Smith, Holly; Atakpa‐Adaji, Peace; Taylor, Colin W.

doi:10.1038/s41467-021-24739-9

Cited by 43 publications

(29 citation statements)

References 79 publications

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“…The cER expansion also impacted the Ca 2+ homeostasis of intracellular Ca 2+ stores, reducing the amount of Ca 2+ mobilized by an InsP3-mediated agonist. This defect was not associated with a reduction of the amount of Ca 2+ released by Tg, suggesting that it could reflect a loss of active InsP3 receptors near sites of store-operated Ca 2+ entry ( Thillaiappan et al, 2021 ). The activity of the PMCA remained unaffected and Ca 2+ influx remained sensitive to the expression of CaM mutants, indicating that the regulation of STIM-ORAI complexes by accessory proteins is conserved.…”

Section: Discussionmentioning

confidence: 99%

Enforced tethering elongates the cortical endoplasmic reticulum and limits store-operated Ca2+ entry

Henry

Carreras-Sureda

Demaurex

2022

Journal of Cell Science

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Recruitment of STIM proteins to cortical ER (cER) domains forming membrane contact sites (MCS) mediate the store-operated Ca2+ entry (SOCE) pathway essential for human immunity. The cER is dynamically regulated by STIM and tethering proteins during SOCE, but the ultrastructural rearrangement and functional consequences of cER remodelling are unknown. Here, we express natural (E-Syt1/2) and artificial (MAPPER-S/L) protein tethers in HEK-293T cells and correlate the changes in cER length and gap distance measured by electron microscopy with ionic fluxes. Native cER cisternae extended during store depletion and remained elongated at constant ER-PM gap distance during subsequent Ca2+ elevations. Tethering proteins enhanced store-dependent cER expansion, anchoring the enlarged cER at tether-specific gap distances of 12-15nm (E-Syts) and 5-9nm (MAPPERs). Cells with artificially extended cER had reduced SOCE and reduced agonist-induced Ca2+ release. SOCE remained modulated by calmodulin and exhibited enhanced Ca2+-dependent inhibition. We propose that cER expansion mediated by ER-PM tethering at a close distance negatively regulates SOCE by confining STIM-ORAI complexes to the periphery of enlarged cER sheets, a process that might participate in the termination of store-operated Ca2+ entry.

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Section: Discussionmentioning

confidence: 99%

Enforced tethering elongates the cortical endoplasmic reticulum and limits store-operated Ca2+ entry

Henry

Carreras-Sureda

Demaurex

2022

Journal of Cell Science

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“…Recent technological advances, utilizing high-speed Total Internal Reflection Microscopy, allow near electrophysiological measurement of the biophysical characteristics of Ca 2+ release through IP3R clusters termed "Ca 2+ puffs" (31,46,(61)(62)(63)(64).…”

Section: Discussionmentioning

confidence: 99%

Functional Determination of Calcium Binding Sites Required for the Activation of Inositol 1,4,5-trisphosphate receptors

Arige

Terry

Wagner

et al. 2022

Preprint

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Inositol 1,4,5-trisphosphate (IP3) receptors (IP3Rs) initiate a diverse array of physiological responses by carefully orchestrating intracellular calcium (Ca2+) signals in response to various external cues. Notably, IP3R channel activity is determined by several obligatory factors including IP3, Ca2+ and ATP. The critical basic amino acid residues in the N-terminal IP3-binding core (IBC) region that facilitate IP3 binding are well characterized. In contrast, the residues conferring the biphasic regulation by Ca2+ are yet to be ascertained. Using comparative structural analysis of Ca2+ binding sites identified in two main families of intracellular Ca2+-release channels, ryanodine receptors (RyRs) and IP3Rs, we identified putative acidic residues coordinating Ca2+ in the cytosolic calcium sensor region in IP3Rs. We determined the consequences of substituting putative Ca2+ binding, acidic residues in IP3R family members. We show that the agonist-induced Ca2+ release, single channel open probability (P0) and Ca2+ sensitivities are markedly altered when the negative charge on the conserved acidic side chain residues are neutralized. Remarkably, neutralizing the negatively charged side chain on two of the residues individually in the putative Ca2+ binding pocket shifted the Ca2+ required to activate IP3R to higher concentrations, indicating that these residues likely are a component of the Ca2+ activation site in IP3R. Taken together, our findings indicate that Ca2+ binding to a well conserved activation site is a common underlying mechanism resulted in increased channel activity shared by IP3Rs and RyRs.

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“…In HEK293 cells, AC1 and AC8 are significantly activated by SOCE ( Fagan et al, 1996 ) and SOCE is known to occur in close proximity to IP 3 Rs ( Sampieri et al, 2018 ). Furthermore, it has been shown that AC8 interacts directly with Orai1, the pore forming subunit of SOCE channels ( Willoughby et al, 2012 ), and in HeLa cells, activation of IP 3 R clusters tethered below the plasma membrane by the KRas-induced actin-interacting protein (KRAP) leads to localised depletion of ER Ca 2+ , which in turn leads to SOCE via the activation of stromal interaction molecule 1 (STIM1) ( Thillaiappan et al, 2021 ). Interestingly, in isolated mouse SAN cells, the SOCE inhibitor SKF-9665 inhibited Ca 2+ influx in SAN in response to pharmacological SR unloading and reduced the spontaneous rate by 27% in these conditions ( Ju et al, 2007 ).…”

Section: Discussionmentioning

confidence: 99%

Inhibition of adenylyl cyclase 1 by ST034307 inhibits IP3-evoked changes in sino-atrial node beat rate

et al. 2022

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Atrial arrhythmias, such as atrial fibrillation (AF), are a major mortality risk and a leading cause of stroke. The IP3 signalling pathway has been proposed as an atrial-specific target for AF therapy, and atrial IP3 signalling has been linked to the activation of calcium sensitive adenylyl cyclases AC1 and AC8. We investigated the involvement of AC1 in the response of intact mouse atrial tissue and isolated guinea pig atrial and sino-atrial node (SAN) cells to the α-adrenoceptor agonist phenylephrine (PE) using the selective AC1 inhibitor ST034307. The maximum rate change of spontaneously beating mouse right atrial tissue exposed to PE was reduced from 14.5% to 8.2% (p = 0.005) in the presence of 1 μM ST034307, whereas the increase in tension generated in paced left atrial tissue in the presence of PE was not inhibited by ST034307 (Control = 14.2%, ST034307 = 16.3%; p > 0.05). Experiments were performed using isolated guinea pig atrial and SAN cells loaded with Fluo-5F-AM to record changes in calcium transients (CaT) generated by 10 μM PE in the presence and absence of 1 μM ST034307. ST034307 significantly reduced the beating rate of SAN cells (0.34-fold decrease; p = 0.003) but did not inhibit changes in CaT amplitude in response to PE in atrial cells. The results presented here demonstrate pharmacologically the involvement of AC1 in the downstream response of atrial pacemaker activity to α-adrenoreceptor stimulation and IP3R calcium release.

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KRAP tethers IP3 receptors to actin and licenses them to evoke cytosolic Ca2+ signals

Cited by 43 publications

References 79 publications

Enforced tethering elongates the cortical endoplasmic reticulum and limits store-operated Ca2+ entry

Enforced tethering elongates the cortical endoplasmic reticulum and limits store-operated Ca2+ entry

Functional Determination of Calcium Binding Sites Required for the Activation of Inositol 1,4,5-trisphosphate receptors

Inhibition of adenylyl cyclase 1 by ST034307 inhibits IP3-evoked changes in sino-atrial node beat rate

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