Mutation of NEKL-4/NEK10 and TTLL genes suppress neuronal ciliary degeneration caused by loss of CCPP-1 deglutamylase function.

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 a tubulin tyrosine ligase-like glutamylase gene. We show that mutation in the ttll-4, ttll-5, or ttll-11 gene suppressed the hyperglutamylation-induced loss of ciliary dye filling 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 localizes to the ciliary base but does not localize to cilia, suggesting an indirect role in ciliary processes. 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 the roles of the tubulin code in human ciliopathies and neurodegenerative diseases.

Patterns of psychotropic drug prescription for U.S. patients with diagnoses of bipolar disorders.

OBJECTIVE: Bipolar disorders are prevalent major illnesses with high rates of morbidity, comorbidity, disability, and mortality. A growing number of psychotropic drugs are used to treat bipolar disorder, often off-label and in untested, complex combinations. METHODS: To quantify utilization rates for psychotropic drug classes, this study used the 2002-2003 U.S. national MarketScan research databases to identify 7,760 persons with ICD-9 bipolar disorder subtypes. Survival analysis was used to estimate times until initial monotherapies were augmented, changed, or discontinued. RESULTS: The most commonly prescribed first drug class was antidepressants (50% of patients), followed by mood stabilizers (25%: anticonvulsants, 17%, and lithium, 8%), sedatives (15%), and antipsychotics (11%). At study midpoint only 44% of patients were receiving monotherapy. Those receiving monotherapy were ranked by initial drug prescribed and percentage of patients (bipolar I and bipolar II): antidepressants (55% and 65%), lithium (51% and 41%), antipsychotics (32% and 31%), anticonvulsants (28% and 29%), and sedatives (28%, 25%). Median time to adding another psychotropic was 2.5-times less than median time to changing the initial treatment (16.4 compared with 40.9 weeks), and stopping was rare. Median weeks until therapy was changed in any way for 25% of patients was as follows: lithium, 29 weeks; antidepressants, 13; anticonvulsants, 13; antipsychotics, 13; and sedatives, 9. CONCLUSIONS: Antidepressants were the first-choice agent twice as often as mood stabilizers. Lithium was sustained longer than monotherapy with other mood stabilizers. Time to augmentation was much shorter than time to change or discontinuation.

Glutamylation Regulates Transport, Specializes Function, and Sculpts the Structure of Cilia.

Ciliary microtubules (MTs) are extensively decorated with post-translational modifications (PTMs), such as glutamylation of tubulin tails. PTMs and tubulin isotype diversity act as a "tubulin code" that regulates cytoskeletal stability and the activity of MT-associated proteins such as kinesins. We previously showed that, in C. elegans cilia, the deglutamylase CCPP-1 affects ciliary ultrastructure, localization of the TRP channel PKD-2 and the kinesin-3 KLP-6, and velocity of the kinesin-2 OSM-3/KIF17, whereas a cell-specific α-tubulin isotype regulates ciliary ultrastructure, intraflagellar transport, and ciliary functions of extracellular vesicle (EV)-releasing neurons. Here we examine the role of PTMs and the tubulin code in the ciliary specialization of EV-releasing neurons using genetics, fluorescence microscopy, kymography, electron microscopy, and sensory behavioral assays. Although the C. elegans genome encodes five tubulin tyrosine ligase-like (TTLL) glutamylases, only ttll-11 specifically regulates PKD-2 localization in EV-releasing neurons. In EV-releasing cephalic male (CEM) cilia, TTLL-11 and the deglutamylase CCPP-1 regulate remodeling of 9+0 MT doublets into 18 singlet MTs. Balanced TTLL-11 and CCPP-1 activity fine-tunes glutamylation to control the velocity of the kinesin-2 OSM-3/KIF17 and kinesin-3 KLP-6 without affecting the intraflagellar transport (IFT) kinesin-II. TTLL-11 is transported by ciliary motors. TTLL-11 and CCPP-1 are also required for the ciliary function of releasing bioactive EVs, and TTLL-11 is itself a novel EV cargo. Therefore, MT glutamylation, as part of the tubulin code, controls ciliary specialization, ciliary motor-based transport, and ciliary EV release in a living animal. We suggest that cell-specific control of MT glutamylation may be a conserved mechanism to specialize the form and function of cilia.