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1.
Although store-operated calcium entry (SOCE) was identified more that two decades ago, understanding the molecular mechanisms that regulate and mediate this process continue to pose a major challenge to investigators in this field. Thus, there has been major focus on determining which of the models proposed for this mechanism is valid and conclusively establishing the components of the store-operated calcium (SOC) channel(s). The transient receptor potential canonical (TRPC) proteins have been suggested as candidate components of the elusive store-operated Ca(2+) entry channel. While all TRPCs are activated in response to agonist-stimulated phosphatidylinositol 4,5, bisphosphate (PIP(2)) hydrolysis, only some display store-dependent regulation. TRPC1 is currently the strongest candidate component of SOC and is shown to contribute to SOCE in many cell types. Heteromeric interactions of TRPC1 with other TRPCs generate diverse SOC channels. Recent studies have revealed novel components of SOCE, namely the stromal interacting molecule (STIM) and Orai proteins. While STIM1 has been suggested to be the ER-Ca(2+) sensor protein relaying the signal to the plasma membrane for activation of SOCE, Orai1 is reported to be the pore-forming component of CRAC channel that mediates SOCE in T-lymphocytes and other hematopoetic cells. Several studies now demonstrate that TRPC1 also associates with STIM1 suggesting that SOC and CRAC channels are regulated by similar molecular components. Interestingly, TRPC1 is also associated with Orai1 and a TRPC1-Orai1-STIM1 ternary complex contributes to SOC channel function. This review will focus on the diverse SOC channels formed by TRPC1 and the suggestion that TRPC1 might serve as a molecular link that determines their regulation by store-depletion. 相似文献
2.
Ong HL Cheng KT Liu X Bandyopadhyay BC Paria BC Soboloff J Pani B Gwack Y Srikanth S Singh BB Gill DL Gill D Ambudkar IS 《The Journal of biological chemistry》2007,282(12):9105-9116
Store-operated calcium entry (SOCE) is a ubiquitous mechanism that is mediated by distinct SOC channels, ranging from the highly selective calcium release-activated Ca2+ (CRAC) channel in rat basophilic leukemia and other hematopoietic cells to relatively Ca2+-selective or non-selective SOC channels in other cells. Although the exact composition of these channels is not yet established, TRPC1 contributes to SOC channels and regulation of physiological function of a variety of cell types. Recently, Orai1 and STIM1 have been suggested to be sufficient for generating CRAC channels. Here we show that Orai1 and STIM1 are also required for TRPC1-SOC channels. Knockdown of TRPC1, Orai1, or STIM1 attenuated, whereas overexpression of TRPC1, but not Orai1 or STIM1, induced an increase in SOC entry and I(SOC) in human salivary gland cells. All three proteins were co-localized in the plasma membrane region of cells, and thapsigargin increased co-immunoprecipitation of TRPC1 with STIM1, and Orai1 in human salivary gland cells as well as dispersed mouse submandibular gland cells. In aggregate, the data presented here reveal that all three proteins are essential for generation of I(SOC) in these cells and that dynamic assembly of TRPC1-STIM1-Orai1 ternary complex is involved in activation of SOC channel in response to internal Ca2+ store depletion. Thus, these data suggest a common molecular basis for SOC and CRAC channels. 相似文献
3.
钙库操纵的钙内流(SOCE)是调节钙离子(Ca2+)内流进入细胞最普遍的一种途径,它的通道称为钙库操纵的钙内流通道(SOC)。SOC存在于大多数非兴奋细胞和部分兴奋细胞上,近年来确定,STIM和Orai是组成SOC的两种主要蛋白质。本文就近年来对SOCE途径的机制,STIM和Orai不同亚型的结构、功能及在心脑血管疾病中的作用作一综述。 相似文献
4.
Orai1 and TRPC1 have been proposed as core components of store-operated calcium release-activated calcium (CRAC) and store-operated calcium (SOC) channels, respectively. STIM1, a Ca(2+) sensor protein in the endoplasmic reticulum, interacts with and mediates store-dependent regulation of both channels. We have previously reported that dynamic association of Orai1, TRPC1, and STIM1 is involved in activation of store-operated Ca(2+) entry (SOCE) in salivary gland cells. In this study, we have assessed the molecular basis of TRPC1-SOC channels in HEK293 cells. We report that TRPC1+STIM1-dependent SOCE requires functional Orai1. Thapsigargin stimulation of cells expressing Orai1+STIM1 increased Ca(2+) entry and activated typical I(CRAC) current. STIM1 alone did not affect SOCE, whereas expression of Orai1 induced a decrease. Expression of TRPC1 induced a small increase in SOCE, which was greatly enhanced by co-expression of STIM1. Thapsigargin stimulation of cells expressing TRPC1+STIM1 activated a non-selective cation current, I(SOC), that was blocked by 1 microm Gd(3+) and 2-APB. Knockdown of Orai1 decreased endogenous SOCE as well as SOCE with TRPC1 alone. siOrai1 also significantly reduced SOCE and I(SOC) in cells expressing TRPC1+STIM1. Expression of R91WOrai1 or E106QOrai1 induced similar attenuation of TRPC1+STIM1-dependent SOCE and I(SOC), whereas expression of Orai1 with TRPC1+STIM1 resulted in SOCE that was larger than that with Orai1+STIM1 or TRPC1+STIM1 but not additive. Additionally, Orai1, E106QOrai1, and R91WOrai1 co-immunoprecipitated with similar levels of TRPC1 and STIM1 from HEK293 cells, and endogenous TRPC1, STIM1, and Orai1 were co-immunoprecipitated from salivary glands. Together, these data demonstrate a functional requirement for Orai1 in TRPC1+STIM1-dependent SOCE. 相似文献
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The stromal interaction molecules STIM1 and STIM2 are Ca(2+) sensors, mostly located in the endoplasmic reticulum, that detect changes in the intraluminal Ca(2+) concentration and communicate this information to plasma membrane store-operated channels, including members of the Orai family, thus mediating store-operated Ca(2+) entry (SOCE). Orai and STIM proteins are almost ubiquitously expressed in human cells, where SOCE has been reported to play a relevant functional role. The phenotype of patients bearing mutations in STIM and Orai proteins, together with models of STIM or Orai deficiency in mice, as well as other organisms such as Drosophila melanogaster, have provided compelling evidence on the relevant role of these proteins in cellular physiology and pathology. Orai1-deficient patients suffer from severe immunodeficiency, congenital myopathy, chronic pulmonary disease, anhydrotic ectodermal dysplasia and defective dental enamel calcification. STIM1-deficient patients showed similar abnormalities, as well as autoimmune disorders. This review summarizes the current evidence that identifies and explains diseases induced by disturbances in SOCE due to deficiencies or mutations in Orai and STIM proteins. 相似文献
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8.
Zhang SL Kozak JA Jiang W Yeromin AV Chen J Yu Y Penna A Shen W Chi V Cahalan MD 《The Journal of biological chemistry》2008,283(25):17662-17671
We evaluated currents induced by expression of human homologs of Orai together with STIM1 in human embryonic kidney cells. When co-expressed with STIM1, Orai1 induced a large inwardly rectifying Ca(2+)-selective current with Ca(2+)-induced slow inactivation. A point mutation of Orai1 (E106D) altered the ion selectivity of the induced Ca(2+) release-activated Ca(2+) (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 Ca(2+) 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 Ca(2+) 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. 相似文献
9.
Takumi Kawasaki Takehiko Ueyama Ingo Lange Stefan Feske Naoaki Saito 《The Journal of biological chemistry》2010,285(33):25720-25730
Ca2+ signals through store-operated Ca2+ (SOC) channels, activated by the depletion of Ca2+ from the endoplasmic reticulum, regulate various physiological events. Orai1 is the pore-forming subunit of the Ca2+ release-activated Ca2+ (CRAC) channel, the best characterized SOC channel. Orai1 is activated by stromal interaction molecule (STIM) 1, a Ca2+ sensor located in the endoplasmic reticulum. Orai1 and STIM1 are crucial for SOC channel activation, but the molecular mechanisms regulating Orai1 function are not fully understood. In this study, we demonstrate that protein kinase C (PKC) suppresses store-operated Ca2+ entry (SOCE) by phosphorylation of Orai1. PKC inhibitors and knockdown of PKCβ both resulted in increased Ca2+ influx. Orai1 is strongly phosphorylated by PKC in vitro and in vivo at N-terminal Ser-27 and Ser-30 residues. Consistent with these results, substitution of endogenous Orai1 with an Orai1 S27A/S30A mutant resulted in increased SOCE and CRAC channel currents. We propose that PKC suppresses SOCE and CRAC channel function by phosphorylation of Orai1 at N-terminal serine residues Ser-27 and Ser-30. 相似文献
10.
Muñoz E Valero RA Quintana A Hoth M Núñez L Villalobos C 《The Journal of biological chemistry》2011,286(18):16186-16196
Abnormal vascular smooth muscle cell (VSMC) proliferation contributes to occlusive and proliferative disorders of the vessel wall. Salicylate and other nonsteroidal anti-inflammatory drugs (NSAIDs) inhibit VSMC proliferation by an unknown mechanism unrelated to anti-inflammatory activity. In search for this mechanism, we have studied the effects of salicylate and other NSAIDs on subcellular Ca(2+) homeostasis and Ca(2+)-dependent cell proliferation in rat aortic A10 cells, a model of neointimal VSMCs. We found that A10 cells displayed both store-operated Ca(2+) entry (SOCE) and voltage-operated Ca(2+) entry (VOCE), the former being more important quantitatively than the latter. Inhibition of SOCE by specific Ca(2+) released-activated Ca(2+) (CRAC/Orai) channels antagonists prevented A10 cell proliferation. Salicylate and other NSAIDs, including ibuprofen, indomethacin, and sulindac, inhibited SOCE and thereby Ca(2+)-dependent, A10 cell proliferation. SOCE, but not VOCE, induced mitochondrial Ca(2+) uptake in A10 cells, and mitochondrial depolarization prevented SOCE, thus suggesting that mitochondrial Ca(2+) uptake controls SOCE (but not VOCE) in A10 cells. NSAIDs depolarized mitochondria and prevented mitochondrial Ca(2+) uptake, suggesting that they favor the Ca(2+)-dependent inactivation of CRAC/Orai channels. NSAIDs also inhibited SOCE in rat basophilic leukemia cells where mitochondrial control of CRAC/Orai is well established. NSAIDs accelerate slow inactivation of CRAC currents in rat basophilic leukemia cells under weak Ca(2+) buffering conditions but not in strong Ca(2+) buffer, thus excluding that NSAIDs inhibit SOCE directly. Taken together, our results indicate that NSAIDs inhibit VSMC proliferation by facilitating the Ca(2+)-dependent inactivation of CRAC/Orai channels which normally is prevented by mitochondria clearing of entering Ca(2+). 相似文献
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Orai1 and hTRPC1 have been presented as essential components of store-operated channels mediating highly Ca(2+) selective I(CRAC) and relatively Ca(2+) selective I(SOC), respectively. STIM1 has been proposed to communicate the Ca(2+) content of the intracellular Ca(2+) stores to the plasma membrane store-operated Ca(2+) channels. Here we present evidence for the dynamic interaction between endogenously expressed Orai1 and both STIM1 and hTRPC1 regulated by depletion of the intracellular Ca(2+) stores, using the pharmacological tools thapsigargin plus ionomycin, or by the physiological agonist thrombin, independently of extracellular Ca(2+). In addition we report that Orai1 mediates the communication between STIM1 and hTRPC1, which is essential for the mode of activation of hTRPC1-forming Ca(2+) permeable channels. Electrotransjection of cells with anti-Orai1 antibody, directed toward the C-terminal region that mediates the interaction with STIM1, and stabilization of an actin cortical barrier with jasplakinolide prevented the interaction between STIM1 and hTRPC1. Under these conditions hTRPC1 was no longer involved in store-operated calcium entry but in diacylglycerol-activated non-capacitative Ca(2+) entry. These findings support the functional role of the STIM1-Orai1-hTRPC1 complex in the activation of store-operated Ca(2+) entry. 相似文献
13.
Zou JJ Gao YD Geng S Yang J 《Journal of applied physiology (Bethesda, Md. : 1985)》2011,110(5):1256-1263
Hyperplasia of airway smooth muscle cells (ASMCs) is a characteristic change of chronic asthma patients. However, the underlying mechanisms that trigger this process are not yet completely understood. Store-operated Ca(2+) (SOC) entry (SOCE) occurs in response to the intracellular sarcoplasma reticulum (SR)/endoplasmic reticulum (ER) Ca(2+) store depletion. SOCE plays an important role in regulating Ca(2+) signaling and cellular responses of ASMCs. Stromal interaction molecule (STIM)1 has been proposed as an ER/SR Ca(2+) sensor and translocates to the ER underneath the plasma membrane upon depletion of the ER Ca(2+) store, where it interacts with Orai1, the molecular component of SOC channels, and brings about SOCE. STIM1 and Orai1 have been proved to mediate SOCE of ASMCs. In this study, we investigated whether STIM1/Orai1-mediated SOCE is involved in rat ASMC proliferation. We found that SOCE was upregulated during ASMC proliferation accompanied by a mild increase of STIM1 and a significant increase of Orai1 mRNA expression, whereas the proliferation of ASMCs was partially inhibited by the SOC channel blockers SKF-96365, NiCl(2), and BTP-2. Suppressing the mRNA expression of STIM1 or Orai1 with specific short hairpin RNA resulted in the attenuation of SOCE and ASMC proliferation. Moreover, after knockdown of STIM1 or Orai1, the SOC channel blocker SKF-96365 had no inhibitory effect on the proliferation of ASMCs anymore. These results suggested that STIM1/Orai1-mediated SOCE is involved in ASMC proliferation. 相似文献
14.
The means by which Ca(2+) store depletion evokes the opening of store-operated Ca(2+) channels (SOCs) in the plasma membrane of excitable and non-excitable cells has been a longstanding mystery. Indirect evidence has supported local interactions between the ER and SOCs as well as long-range interactions mediated through a diffusible activator. The recent molecular identification of the ER Ca(2+) sensor (STIM1) and a subunit of the CRAC channel (Orai1), a prototypic SOC, has now made it possible to visualize directly the sequence of events that links store depletion to CRAC channel opening. Following store depletion, STIM1 moves from locations throughout the ER to accumulate in ER subregions positioned within 10-25nm of the plasma membrane. Simultaneously, Orai1 gathers at discrete sites in the plasma membrane directly opposite STIM1, resulting in local CRAC channel activation. These new studies define the elementary units of store-operated Ca(2+) entry, and reveal an unprecedented mechanism for channel activation in which the stimulus brings a channel and its activator/sensor together for interaction across apposed membrane compartments. We discuss the implications of this choreographic mechanism with regard to Ca(2+) dynamics, specificity of Ca(2+) signaling, and the existence of a specialized ER subset dedicated to the control of the CRAC channel. 相似文献
15.
The activation of Ca(2+) entry through store-operated channels by agonists that deplete Ca(2+) from the endoplasmic reticulum (ER) is an ubiquitous signaling mechanism, the molecular basis of which has remained elusive for the past 20 years. In T lymphocytes, store-operated Ca(2+)-release-activated Ca(2+) (CRAC) channels constitute the sole pathway for Ca(2+) entry following antigen-receptor engagement, and their function is essential for driving the program of gene expression that underlies T-cell activation by antigen. The first molecular components of this pathway have recently been identified: stromal interaction molecule 1 (STIM1), the ER Ca(2+) sensor, and Orai1, a pore-forming subunit of the CRAC channel. Recent work shows that CRAC channels are activated in a complex fashion that involves the co-clustering of STIM1 in junctional ER directly opposite Orai1 in the plasma membrane. These studies reveal an abundance of sites where Ca(2+) signaling might be controlled to modulate the activity of T cells during the immune response. 相似文献
16.
Gwozdz T Dutko-Gwozdz J Zarayskiy V Peter K Bolotina VM 《American journal of physiology. Cell physiology》2008,295(5):C1133-C1140
Stromal interaction molecule 1 (STIM1) and Orai1 have been identified as crucial elements of the store-operated Ca(2+) entry (SOCE) pathway, but the mechanism of their functional interaction remains controversial. It is now well established that, upon depletion of the stores, both molecules can accumulate and colocalize in specific areas (puncta) where the endoplasmic reticulum comes in close proximity to the plasma membrane. Some models propose a direct interaction between STIM1 and Orai1 as the most straightforward mechanism for signal transduction from the stores to the plasma membrane. To test some of the predictions of a conformational coupling model, we assessed how tight the relationships are between STIM1 and Orai1 expression, puncta formation, and SOCE activation. Here we present evidence that STIM1 accumulates in puncta equally well in the presence or absence of Orai1 expression, that STIM1 accumulation is not sufficient for Orai1 accumulation in the same areas, and that normal Ca(2+) release-activated Ca(2+) current (I(CRAC)) can be activated in STIM1-deficient cells. These data challenge the idea of direct conformational coupling between STIM1 and Orai1 as a viable mechanism of puncta formation and SOCE activation and uncover greater complexity in their relationship, which may require additional intermediate elements. 相似文献
17.
Ca(2+) signals are universal among cells in regulating a spectrum of cellular responses. Phospholipase C-coupled receptors activate two components of Ca(2+) signals--rapid Ca(2+) release from ER stores, followed by slower Ca(2+) entry from outside the cell. The coupling process between ER and PM to mediate this "store-operated" Ca(2+) entry process remained until recently a molecular mystery. The recent discovery of the necessity for STIM1 and Orai proteins in this process has provided crucial information on the coupling mechanism between stores and PM Ca(2+) entry. STIM1 is a single spanning membrane protein with an unpaired Ca(2+) binding EF-hand and appears to function as the sensor of ER luminal Ca(2+), and, through redistribution in the ER, transduces information directly to the PM. Orai1 is a tetra-spanning PM protein and functions as the highly Ca(2+)-selective channel in the PM that is gated through interactions with the store-activated ER Ca(2+) sensor. Recent evidence shows the two proteins together are necessary and sufficient for the function of store-operated Ca(2+) entry. However, many questions arise about how and where the interactions of the STIM1 and Orai1 proteins occur within cells. Here we discuss recent information and ideas about the coupling between these proteins that leads to store-operated channel activation. 相似文献
18.
Store-operated Ca2+ entry (SOCE) is a widespread mechanism to elevate the intracellular Ca2+ concentrations and stimulate downstream signaling pathways affecting proliferation, secretion, differentiation and death in different cell types. In immune cells, immune receptor stimulation induces intracellular Ca2+ store depletion that subsequently activates Ca2+-release-activated-Ca2+ (CRAC) channels, a prototype of store-operated Ca2+ (SOC) channels. CRAC channel opening leads to activation of diverse downstream signaling pathways affecting proliferation, differentiation, cytokine production and cell death. Recent identification of STIM1 as the endoplasmic reticulum Ca2+ sensor and Orai1 as the pore subunit of CRAC channels has provided the much-needed molecular tools to dissect the mechanism of activation and regulation of CRAC channels. In this review, we discuss the recent advances in understanding the associating partners and posttranslational modifications of Orai1 and STIM1 proteins that regulate diverse aspects of CRAC channel function. 相似文献
19.
The elementary unit of store-operated Ca2+ entry: local activation of CRAC channels by STIM1 at ER-plasma membrane junctions
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The activation of store-operated Ca(2+) entry by Ca(2+) store depletion has long been hypothesized to occur via local interactions of the endoplasmic reticulum (ER) and plasma membrane, but the structure involved has never been identified. Store depletion causes the ER Ca(2+) sensor stromal interacting molecule 1 (STIM1) to form puncta by accumulating in junctional ER located 10-25 nm from the plasma membrane (see Wu et al. on p. 803 of this issue). We have combined total internal reflection fluorescence (TIRF) microscopy and patch-clamp recording to localize STIM1 and sites of Ca(2+) influx through open Ca(2+) release-activated Ca(2+) (CRAC) channels in Jurkat T cells after store depletion. CRAC channels open only in the immediate vicinity of STIM1 puncta, restricting Ca(2+) entry to discrete sites comprising a small fraction of the cell surface. Orai1, an essential component of the CRAC channel, colocalizes with STIM1 after store depletion, providing a physical basis for the local activation of Ca(2+) influx. These studies reveal for the first time that STIM1 and Orai1 move in a coordinated fashion to form closely apposed clusters in the ER and plasma membranes, thereby creating the elementary unit of store-operated Ca(2+) entry. 相似文献
20.
Store-operated calcium entry (SOCE) is a major mechanism for Ca2+ entry in excitable and non-excitable cells. The best-characterised store-operated current is ICRAC, but other currents activated by Ca2+ store depletion have also been reported. The recent identification of the proteins stromal interaction molecule 1 (STIM1) and Orai1 has shed new light on the nature and regulation of SOC channels. STIM1 has been presented as the endoplasmic reticulum (ER) Ca2+ sensor that communicates the content of the Ca2+ stores to the store-operated channels, a mechanism that involves redistribution of STIM1 to peripheral ER sites and co-clustering with the Ca2+ channel subunit, Orai1. Interestingly, TRPC1, which has long been proposed as a SOC channel candidate, associates with Orai1 and STIM1 in a ternary complex that appears to increase the variability of SOC currents available to modulate cell function. 相似文献