Increased Polyubiquitination and Proteasomal Degradation of a Munc18-1 Disease-Linked Mutant Causes Temperature-Sensitive Defect in Exocytosis
Increased Polyubiquitination and Proteasomal Degradation of a Munc18-1 Disease-Linked Mutant Causes Temperature-Sensitive Defect in Exocytosis
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DOI：
10.1016/j.celrep.2014.08.059
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发表时间：
2014-10-09
期刊：
影响因子：
8.8
通讯作者：
Meunier, Frederic A.
中科院分区：
文献类型：
--
作者：
Martin, Sally;Papadopulos, Andreas;Meunier, Frederic A.
Munc18-1是控制神经胞吐作用的核心机制的关键组成部分。最近，Munc18-1的突变导致早期婴儿癫痫性脑病的发展已被发现。然而，哪种降解途径控制Munc18-1水平以及它如何影响这种病理中的神经胞吐尚不清楚。利用缺乏Munc18的神经分泌细胞，我们发现一种与疾病相关的突变C180Y使该蛋白在37℃时不稳定。尽管突变蛋白保留其作为t-SNARE伴侣的功能，但神经胞分泌功能受损，这一缺陷可以在较低的允许温度下恢复。我们发现Munc18-1经历了k48相关的多泛素化，突变导致蛋白酶体降解，而不是溶酶体降解。我们的数据表明功能性Munc18-1水平是通过多泛素化和蛋白酶体降解来控制的。C180Y致病突变极大地增强了这种降解途径，使Munc18-1无法促进神经胞分泌，这种表型在允许的温度下被逆转。
Munc18-1 is a critical component of the core machinery controlling neuroexocytosis. Recently, mutations in Munc18-1 leading to the development of early infantile epileptic encephalopathy have been discovered. However, which degradative pathway controls Munc18-1 levels and how it impacts on neuroexocytosis in this pathology is unknown. Using neurosecretory cells deficient in Munc18, we show that a disease-linked mutation, C180Y, renders the protein unstable at 37 degrees C. Although the mutated protein retains its function as t-SNARE chaperone, neuroexocytosis is impaired, a defect that can be rescued at a lower permissive temperature. We reveal that Munc18-1 undergoes K48-linked polyubiquitination, which is highly increased by the mutation, leading to proteasomal, but not lysosomal, degradation. Our data demonstrate that functional Munc18-1 levels are controlled through polyubiquitination and proteasomal degradation. The C180Y disease-causing mutation greatly potentiates this degradative pathway, rendering Munc18-1 unable to facilitate neuroexocytosis, a phenotype that is reversed at a permissive temperature.