Munc13-4 is a GTP-Rab27-binding protein regulating dense core granule secretion in platelets
Munc13-4 is a GTP-Rab27-binding protein regulating dense core granule secretion in platelets
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DOI：
10.1074/jbc.m309426200
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发表时间：
2004-03-12
影响因子：
4.8
通讯作者：
Horiuchi, H
中科院分区：
文献类型：
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作者：
Shirakawa, R;Higashi, T;Horiuchi, H
血小板在致密的核心颗粒中储存自身激动剂，如ADP和5-羟色胺。虽然这些颗粒的胞吐作用对于止血和血栓形成至关重要，但其潜在机制尚未完全了解。在这里，我们表明，与unprenylated活性突变体Rab 27 A-Q78 L，野生型Rab 27 A和Rab 27 B的孵育透化血小板抑制分泌，而非活性突变体Rab 27 A-T23 N和其他GTP酶没有影响。此外，我们亲和纯化了血小板中的GTP-Rab 27 A结合蛋白，并将其鉴定为Munc 13 -4，Munc 13 -1的同源物，被称为神经递质释放的引发因子。重组Munc 13 -4在体外直接结合GTP-Rab 27 A和-Rab 27 B，但不结合其他GTP酶，并在体外测定中增强分泌。通过添加Munc 13 -4来挽救未异戊二烯化Rab 27 A对分泌的抑制，表明Munc 13 -4介导GTP-Rab 27的功能。因此，Rab 27通过其结合蛋白Munc 13 -4调节血小板中致密核心颗粒的分泌。
Platelets store self-agonists such as ADP and serotonin in dense core granules. Although exocytosis of these granules is crucial for hemostasis and thrombosis, the underlying mechanism is not fully understood. Here, we show that incubation of permeabilized platelets with unprenylated active mutant Rab27A-Q78L, wild type Rab27A, and Rab27B inhibited the secretion, whereas inactive mutant Rab27A-T23N and other GTPases had no effects. Furthermore, we affinity-purified a GTP-Rab27A-binding protein in platelets and identified it as Munc13-4, a homologue of Munc13-1 known as a priming factor for neurotransmitter release. Recombinant Munc13-4 directly bound to GTP-Rab27A and - Rab27B in vitro, but not other GTPases, and enhanced secretion in an in vitro assay. The inhibition of secretion by unprenylated Rab27A was rescued by the addition of Munc13-4, suggesting that Munc13-4 mediates the function of GTP-Rab27. Thus, Rab27 regulates the dense core granule secretion in platelets by employing its binding protein, Munc13-4.