Ciliary microtubules are subject to post-translational modifications that act as a Tubulin Code to regulate motor traffic, binding proteins and stability. In humans, loss of CCP1, a cytosolic carboxypeptidase and tubulin deglutamylating enzyme, causes infantile-onset neurodegeneration. In C.elegans, mutations in ccpp-1, the homolog of CCP1, result in progressive degeneration of neuronal cilia and loss of neuronal function. To identify genes that regulate microtubule glutamylation and ciliary integrity, we performed a forward genetic screen for suppressors of ciliary degeneration in ccpp-1 mutants. We isolated the ttll-5(my38) suppressor, a mutation in the tubulin tyrosine ligase-like glutamylase gene. We show that mutation in ttll-4, ttll-5, or ttll-11 gene suppressed the hyperglutamylation-induced loss of microtubules and kinesin-2 mislocalization in ccpp-1 cilia. We also identified the nekl-4(my31) suppressor, an allele affecting the NIMA (Never in Mitosis A)-related kinase NEKL-4/NEK10. In humans, NEK10 mutation causes bronchiectasis, an airway and mucociliary transport disorder caused by defective motile cilia. C. elegans NEKL-4 does not localize to cilia yet plays a role in regulating axonemal microtubule stability. This work defines a pathway in which glutamylation, a component of the Tubulin Code, is written by TTLL-4, TTLL-5, and TTLL-11; is erased by CCPP-1; is read by ciliary kinesins; and its downstream effects are modulated by NEKL-4 activity. Identification of regulators of microtubule glutamylation in diverse cellular contexts is important to the development of effective therapies for disorders characterized by changes in microtubule glutamylation. By identifying C. elegans genes important for neuronal and ciliary stability, our work may inform research into human ciliopathies and neurodegenerative diseases.

中文翻译：

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NEKL-4 / NEK10和TTLL基因的突变反对CCPP-1脱谷氨酰胺酶的丢失并防止神经元睫状变性

睫状微管经过翻译后修饰，可作为微管蛋白密码来调节运动量，结合蛋白和稳定性。在人类中，CCP1（一种胞质羧肽酶和微管蛋白脱谷氨酰化酶）的丢失会导致婴儿发作的神经变性。在秀丽隐杆线虫中，ccp-1（CCP1的同源物）的突变导致神经元纤毛进行性变性和神经元功能丧失。为了鉴定调节微管谷氨酰化和睫状完整性的基因，我们对ccpp-1突变体中的睫状变性抑制因子进行了正向遗传筛选。我们分离了ttll-5（my38）抑制子，微管蛋白酪氨酸连接酶样谷氨酰胺酶基因中的一个突变。我们显示ttll-4，ttll-5中的突变 或ttll-11基因抑制ccpp-1纤毛中高谷氨酰化诱导的微管丢失和kinesin-2错位。我们还确定了nekl-4（my31）抑制剂，一个等位基因，它影响NIMA（永无丝分裂A）相关激酶NEKL-4 / NEK10。在人类中，NEK10突变会引起支气管扩张，这是由运动性纤毛缺陷引起的气道和粘膜纤毛运输障碍。秀丽隐杆线虫NEKL-4并不局限于纤毛，但在调节轴突微管稳定性中起作用。这项工作定义了一条途径，其中TTLL-4，TTLL-5和TTLL-11编写了微管蛋白密码的一部分-谷氨酰化；被CCPP-1擦除；由睫状驱动蛋白读取；其下游作用受NEKL-4活性调节。在多种细胞环境中鉴定微管谷氨酰化调节剂对于开发以微管谷氨酰化变化为特征的疾病的有效疗法至关重要。通过鉴定对神经元和睫毛稳定性重要的秀丽隐杆线虫基因，我们的工作可能会为人类纤毛病和神经退行性疾病的研究提供参考。