Munc18b is an essential gene in mice whose expression is limiting for secretion by airway epithelial and mast cells.
Munc18b is an essential gene in mice whose expression is limiting for secretion by airway epithelial and mast cells.
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DOI：
10.1042/bj20120057
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发表时间：
2012-09-15
期刊：
影响因子：
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通讯作者：
Dickey BF
中科院分区：
文献类型：
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作者：
Kim K;Petrova YM;Scott BL;Nigam R;Agrawal A;Evans CM;Azzegagh Z;Gomez A;Rodarte EM;Olkkonen VM;Bagirzadeh R;Piccotti L;Ren B;Yoon JH;McNew JA;Adachi R;Tuvim MJ;Dickey BF
必须严格控制气道粘蛋白分泌和 MC（肥大细胞）脱粒，以分别维持肺部和免疫系统的稳态。我们发现胞吐蛋白Munc18b在小鼠气道上皮细胞和MC中高表达，并且定位于气道分泌细胞的顶极。为了解决其功能，我们创建了一只具有严重低效型 Munc18b 等位基因的小鼠，使得杂合子中的蛋白质表达减少了约 50%。纯合突变小鼠无法存活，但杂合子的上皮细胞粘蛋白刺激释放和 MC 颗粒含量减少约 50%。 MC 的缺陷仅影响调节性分泌，而不影响组成型或转运蛋白介导的分泌。被动皮肤过敏反应的严重程度也降低了约 50%，表明 Munc18b 表达的减少导致依赖 MC 脱颗粒的生理反应减弱。 Munc18b启动子由气道上皮细胞中的INR（启动子）、Sp1（特异性蛋白1）、Ets、CRE（cAMP反应元件）、GRE（糖皮质激素反应元件）、GATA和E-box元件控制；然而，在过敏性炎症引起的粘膜化生过程中，蛋白质水平没有变化。总而言之，本研究的结果确定 Munc18b 是一个必需基因，是上皮细胞和 MC 胞吐机制的限制成分。
Airway mucin secretion and MC (mast cell) degranulation must be tightly controlled for homoeostasis of the lungs and immune system respectively. We found the exocytic protein Munc18b to be highly expressed in mouse airway epithelial cells and MCs, and localized to the apical pole of airway secretory cells. To address its functions, we created a mouse with a severely hypomorphic Munc18b allele such that protein expression in heterozygotes was reduced by ~50%. Homozygous mutant mice were not viable, but heterozygotes showed a ~50% reduction in stimulated release of mucin from epithelial cells and granule contents from MCs. The defect in MCs affected only regulated secretion and not constitutive or transporter-mediated secretion. The severity of passive cutaneous anaphylaxis was also reduced by ~50%, showing that reduction of Munc18b expression results in an attenuation of physiological responses dependent on MC degranulation. The Munc18b promoter is controlled by INR (initiator), Sp1 (specificity protein 1), Ets, CRE (cAMP-response element), GRE (glucocorticoid-response element), GATA and E-box elements in airway epithelial cells; however, protein levels did not change during mucous metaplasia induced by allergic inflammation. Taken together, the results of the present study identify Munc18b as an essential gene that is a limiting component of the exocytic machinery of epithelial cells and MCs.