Orai1 (CRACM1) is the platelet SOC channel and essential for pathological thrombus formation

Rudolf Virchow Center, DFG Research Center for Experimental Biomedicine, Würzburg, Germany.
Blood (Impact Factor: 10.45). 11/2008; 113(9):2056-63. DOI: 10.1182/blood-2008-07-171611
Source: PubMed


Platelet activation and aggregation at sites of vascular injury are essential for primary hemostasis, but are also major pathomechanisms underlying myocardial infarction and stroke. Changes in [Ca(2+)](i) are a central step in platelet activation. In nonexcitable cells, receptor-mediated depletion of intracellular Ca(2+) stores triggers Ca(2+) entry through store-operated calcium (SOC) channels. STIM1 has been identified as an endoplasmic reticulum (ER)-resident Ca(2+) sensor that regulates store-operated calcium entry (SOCE) in immune cells and platelets, but the identity of the platelet SOC channel has remained elusive. Orai1 (CRACM1) is the recently discovered SOC (CRAC) channel in T cells and mast cells but its role in mammalian physiology is unknown. Here we report that Orai1 is strongly expressed in human and mouse platelets. To test its role in blood clotting, we generated Orai1-deficient mice and found that their platelets display severely defective SOCE, agonist-induced Ca(2+) responses, and impaired activation and thrombus formation under flow in vitro. As a direct consequence, Orai1 deficiency in mice results in resistance to pulmonary thromboembolism, arterial thrombosis, and ischemic brain infarction, but only mild bleeding time prolongation. These results establish Orai1 as the long-sought platelet SOC channel and a crucial mediator of ischemic cardiovascular and cerebrovascular events.

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Available from: Markus Bender, Jan 20, 2014
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    • "At testing, mice were restrained in a plexiglass chamber during the measurement of bleed time. Methods for determining bleed time have been described previously (Braun et al., 2009). A 3-mm segment of the tail was removed using surgical scissors, and tail bleeding was monitored by gently blotting drops of blood leaving the tail with filter paper every 20 seconds. "
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    ABSTRACT: There are ongoing efforts to develop pain therapeutics with novel mechanisms of action that avoid common side effects associated with other analgesics. The anticonvulsant neuropeptide galanin is a potent regulator of neuronal excitability and has a well-established role in pain modulation, making it a potential target for novel therapies. Our previous efforts focused on improving blood-brain-barrier penetration and enhancing the metabolic stability of galanin analogs to protect against seizures. More recently, we designed peripherally-acting galanin analogs that reduce pain-related behaviors by acting in the periphery and exhibit preferential binding towards GAL2 over GAL1 galanin receptors. Here we report preclinical studies of a monodisperse oligoethylene glycol (dPEG)-containing galanin analog, NAX 409-9 (previously reported as Gal-R2-dPEG24 in Zhang et al., 2013), in rodent analgesic and safety models. Results obtained with NAX 409-9 in these tests were compared to the representative analgesics gabapentin, ibuprofen, acetylsalicylic acid, acetaminophen, and morphine. In mice that received intraplantar carrageenan, NAX 409-9 increased paw withdrawal latency with an ED50 of 6.6 mg/kg, i.p. NAX 409-9 also increased the paw withdrawal threshold to mechanical stimulation following partial sciatic nerve ligation in rats (2 mg/kg). Conversely, NAX 409-9 had no effect in the tail flick or hot plate assays (up to 24 mg/kg). Importantly, NAX 409-9 did not negatively affect gastrointestinal motility (4-20 mg/kg), respiratory rate (40-80 mg/kg), or bleed time (20 mg/kg). These studies illustrate that this non-brain-penetrating galanin analog reduces pain behaviors in several models and does not produce some of the dose-limiting toxicities associated with other analgesics.
    Journal of Pharmacology and Experimental Therapeutics 10/2014; 352(1). DOI:10.1124/jpet.114.219063 · 3.97 Impact Factor
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    • "Our previous study indicated that genetic polymorphisms of ORAI1 are associated with susceptibility to calcium urolithiasis [6]. ORAI1 is a pore subunit of the SOC channel involved in different physiological functions, including immune responses and inflammatory reactions [24]. Indeed, calcium influx through the SOC channel can regulate the secretion of proinflammatory molecules such as arachidonic acid and leukotriene C4 [25]. "
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    03/2014; 2014:397826. DOI:10.1155/2014/397826
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    • "Independent of the signaling pathway triggered by any of the physiological platelet agonists, a sustained and significant increase in intracellular calcium concentration [Ca 2+ ] i occurs. This increase consists of the release of compartmentalized calcium through the store-operated Ca 2+ entry (SOCE) (Alonso et al., 1991) and the entry of extracellular Ca 2+ at the plasma membrane through the stromal interaction molecule (STIM1), a sensor in the dense tubular system, and Orai1, the major store-operated Ca 2+ (SOC) channel in the plasma membrane or the Na + /Ca 2+ exchanger (Braun et al., 2009), contributing to hemostatic platelet responses. The Epithelial sodium channel/Degenerin (ENaC/Deg) family comprises cation-selective ion channels found widely expressed in animals from hydra and nematodes to vertebrates. "
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