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Acknowledgements: The authors are grateful to the other members of the Boletta laboratory for useful discussions and to L. Tronci for helpful suggestions on data analysis. This work was supported by the Italian Ministry of Health (RF-2018-12368254; RF-2016-02361267 to A.B.; GR-2016-02364851 to C.P. and R.P.), the Italian association of patients with PKD (AIRP to A.B.), the PKD Foundation (218G18 to A.B.), the European Community (H-2020-MSCA-ITN-2019#SCiLS to A.B. and R.R.), by the Italian association for research on cancer (AIRC, IG2019-23513 to A.B.), by Q12 grant (MRC_MC_UU_12022/6 to C.F.), the European Research Council (ERC819920 to C.F.), and the CRUK Programme Foundation (Award C51061/A27453 to C.F.). The authors are grateful to S. Bramani for her continuous support. Part of this work was carried out in ALEMBIC, an advanced microscopy laboratory established by IRCCS Ospedale San Raffaele and Università Vita-Salute San Raffaele. Part of the present work was performed by M.E.S. and A.K.N. in fulfilment of the requirements for obtaining a PhD degree at Vita-Salute San Raffaele University, Milano, Italy., Funder: EC | EC Seventh Framework Programm | FP7 People: Marie-Curie Actions (FP7-PEOPLE - Specific Programme "People" Implementing the Seventh Framework Programme of the European Community for Research, Technological Development and Demonstration Activities (2007 to 2013)); doi: https://doi.org/10.13039/100011264; Grant(s): H2020-MSCA-ITN-2019#SCiLS, H2020-MSCA-ITN-2019#SCiLS, Funder: EC | EC Seventh Framework Programm | FP7 Ideas: European Research Council (FP7-IDEAS-ERC - Specific Programme: "Ideas" Implementing the Seventh Framework Programme of the European Community for Research, Technological Development and Demonstration Activities (2007 to 2013)); doi: https://doi.org/10.13039/100011199; Grant(s): ERC819920, Depriving cells of nutrients triggers an energetic crisis, which is resolved by metabolic rewiring and organelle reorganization. Primary cilia are microtubule-based organelles at the cell surface, capable of integrating multiple metabolic and signalling cues, but their precise sensory function is not fully understood. Here we show that primary cilia respond to nutrient availability and adjust their length via glutamine-mediated anaplerosis facilitated by asparagine synthetase (ASNS). Nutrient deprivation causes cilia elongation, mediated by reduced mitochondrial function, ATP availability and AMPK activation independently of mTORC1. Of note, glutamine removal and replenishment is necessary and sufficient to induce ciliary elongation or retraction, respectively, under nutrient stress conditions both in vivo and in vitro by restoring mitochondrial anaplerosis via ASNS-dependent glutamate generation. Ift88-mutant cells lacking cilia show reduced glutamine-dependent mitochondrial anaplerosis during metabolic stress, due to reduced expression and activity of ASNS at the base of cilia. Our data indicate a role for cilia in responding to, and possibly sensing, cellular glutamine levels via ASNS during metabolic stress.

ObjectiveWe hypothesize alterations in the quality and quantity of anti–43-kDa TAR DNA-binding protein (TDP-43) naturally occurring autoantibodies (NAbs) in patients with amyotrophic lateral sclerosis (ALS); therefore, we assessed relative binding properties of anti–TDP-43 NAbs composite in plasma from patients with ALS in comparison with healthy individuals.MethodsELISA competition assay was used to explore the apparent avidity/affinity of anti–TDP-43 NAbs in plasma from 51 normal controls and 30 patients with ALS. Furthermore, the relative levels of anti–TDP-43 NAbs within the immunoglobulin (Ig) classes of IgG (isotype IgG1-4) and IgMs were measured using classical indirect ELISA. The occurring results were hereafter correlated with the measures of disease duration and disease progression.ResultsHigh-avidity/affinity anti–TDP-43 NAbs levels were significantly reduced in plasma samples from patients with ALS. In addition, a significant decrease in relative levels of anti–TDP-43 IgG3 and IgM NAbs and a significant increase in anti–TDP-43 IgG4 NAbs were observed in ALS plasma vs controls. Furthermore, a decrease in global IgM and an increase in IgG4 levels were observed in ALS. These aberrations of humoral immunity correlated with disease duration, but did not correlate with ALS Functional Rating Scale–Revised scores.ConclusionsOur results may suggest TDP-43–specific immune aberrations in patients with ALS. The skewed immune profiles observed in patients with ALS could indicate a deficiency in the clearance capacity and/or blocking of TDP-43 transmission and propagation. The decrease in levels of high affinity/avidity anti-TDP-43 NAbs and IgMs correlates with disease progression and may be disease predictors.