Editorial: The Role of Optineurin in Immunity and Immune-Mediated Diseases.

The multifunctional adaptor optineurin has been implicated in an increasing number of protein-protein interactions and cellular functions ever since its first identification as a binding partner for an adenoviral protein (1). Most—if not all—optineurin functions require its ubiquitin-binding domain in its C-terminus, which binds to K63- and/or M1-polyubiquinated proteins, allowing it to act, for example, as an adaptor during inflammatory signaling, autophagy, and vesicle trafficking (2–4). The interest in optineurin intensified after the identification of various mutations and polymorphisms in several human diseases, including primary open-angle glaucoma, amyotrophic lateral sclerosis (ALS), Paget's disease of the bone, and Crohn's disease. With their distinct yet unresolved pathogenesis, and complex genetic and environmental risk factors, these diseases seem unrelated at first. ALS, glaucoma, or Paget's disease are not traditionally regarded as immune-mediated diseases; however, the emerging evidence pinpoints immune system disfunction as their common denominator (5, 6). The aim of this Research Topic was to explore the role(s) of optineurin on a host of diverse cellular pathways that are directly or indirectly linked to the immune response. The articles cover immune signaling, cell death, membrane trafficking, autophagy of intracellular bacteria (xenophagy), damaged mitochondria (mitophagy), and protein aggregates.AS thanks the Medical Research Council (MR/L000261/1) for financial support. FB thanks the Medical Research Council (MR/K000888/1 and MR/N000048/1) and the BBSRC (BB/R001316/1). IM thanks the Croatian Science Foundation (IP-2018-01-8563) and the support of the University of Rijeka (18-211-1369)

Optineurin Dysfunction in Amyotrophic Lateral Sclerosis: Why So Puzzling?

Mutations in optineurin have been linked to amyotrophic lateral sclerosis (ALS) a decade ago, but its exact role in the neurodegenerative process is still unclear. As a lysine 63 (K63) and methionine (M1) poly-ubiquitin binding protein, optineurin has been reported to act as an adaptor in inflammatory signaling pathways mediated via nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kB) and interferon regulatory factor 3 (IRF3), as well as in membrane-associated trafficking events including autophagy, maintenance of the Golgi apparatus, and exocytosis. Other studies have demonstrated its role in other processes such as regulation of mitosis, transcription, necroptosis and apoptosis. However, many of the reported effects in cell models have been proven difficult to reproduce in optineurin animal models, demonstrating the challenges of extrapolation between model systems. Knowing that multifunctional proteins present a “nightmare” for researchers, to help navigating through this field, we address the most common controversies, open questions, and artefacts related to optineurin and its role in pathogenesis of ALS and other neurodegenerative diseases.</p

Détermination de signaux requis pour le développement et l'activation des cellules T

Le potentiel d'activation des cellules T et leur capacité à se développer et se différencier dépendent des propriétés intrinsèques du complexe TCR (affinité et expression) et de la signalisation fournie par les molécules de co-stimulation et les cytokines. Nous avonsétudié trois aspects différents d'activation des cellules T et sommes parvenus aux résultatssuivants: (1) Nous trouvons le plus grand taux d'internalisation constitutif de TCR dans les cellules déficientes pour la chaîne du TCR (importante pour l'assemblage et l'activation du TCR). Le mécanisme de la stabilisation du TCR en surface ne dépendait pas des motifs spe cifiques de mais de la longueur du domaine intracellulaire, suggérant fortement que agit en bloquant des motifs d'internalisation d'autres chaînes du TCR. (2) La prolifération des cellules T in vitro dépend de la force et de la durée des stimulations.Quand deux stimulis subliminaux sont séparés dans le temps, les cellules TPARIS5-BU-Necker : Fermée (751152101) / SudocSudocFranceF

Ageing-Induced Decline in Primary Myeloid Cell Phagocytosis Is Unaffected by Optineurin Insufficiency

Optineurin is a ubiquitin-binding adaptor protein involved in multiple cellular processes, including innate inflammatory signalling. Mutations in optineurin were found in amyotrophic lateral sclerosis, an adult-onset fatal neurodegenerative disease that targets motor neurons. Neurodegeneration results in generation of neuronal debris, which is primarily cleared by myeloid cells. To assess the role of optineurin in phagocytosis, we performed a flow cytometry-based phagocytic assay of apoptotic neuronal debris and E. coli bioparticles in bone marrow-derived macrophages (BMDMs), and primary neonatal microglia from wild-type (WT) and optineurin-insufficient (Optn470T) mice. We found no difference in phagocytosis efficiency and the accompanying cytokine secretion in WT and Optn470T BMDMs and microglia. This was true at both steady state and upon proinflammatory polarization with lipopolysaccharide. When we analysed the effect of ageing as a major risk factor for neurodegeneration, we found a substantial decrease in the percentage of phagocytic cells and proinflammatory cytokine secretion in BMDMs from 2-year-old mice. However, this ageing-induced phagocytic decline was unaffected by optineurin insufficiency. All together, these results indicate that ageing is the factor that perturbs normal phagocytosis and proinflammatory cytokine secretion, but that optineurin is dispensable for these processes

Optineurin Deficiency and Insufficiency Lead to Higher Microglial TDP-43 Protein Levels.

Mutations in optineurin, a ubiquitin-binding adaptor protein, cause amyotrophic lateral sclerosis (ALS), a fatal neurodegenerative disease of motor neurons linked to chronic inflammation and protein aggregation. The majority of ALS patients, including those carrying the optineurin mutations, exhibit cytoplasmic mislocalization, ubiquitination, and aggregation of nuclear TAR DNA-binding protein 43 kDa (TDP-43). To address the crosstalk between optineurin and TDP-43, we generated optineurin knockout (KO) neuronal and microglial cell lines using the CRISPR/Cas9 approach. Interestingly, we observed that loss of optineurin resulted in elevated TDP-43 protein expression in microglial BV2 but not neuronal Neuro 2a and NSC-34 cell lines. No changes were observed at the mRNA level, suggesting that this increase was post-translationally regulated. To confirm this observation in primary cells, we then used microglia and macrophages from an optineurin loss-of-function mouse model that lacks the C-terminal ubiquitin-binding region (Optn470T), mimicking optineurin truncations in ALS patients. As observed in the BV2 cells, we also found elevated basal levels of TDP-43 protein in Optn470T microglia and bone marrow-derived macrophages. To test if inflammation could further enhance TDP-43 accumulation in cells lacking functional optineurin, we stimulated them with lipopolysaccharide (LPS), and we observed a significant increase in TDP-43 expression following LPS treatment of WT cells. However, this was absent in both BV2 Optn KO and primary Optn470T microglia, which exhibited the same elevated TDP-43 levels as in basal conditions. Furthermore, we did not observe nuclear TDP-43 depletion or cytoplasmic aggregate formation in either Optn470T microglia or LPS-treated WT or Optn470T microglia. Taken together, our results show that optineurin deficiency and insufficiency post-translationally upregulate microglial TDP-43 protein levels and that elevated TDP-43 levels in cells lacking functional optineurin could not be further increased by an inflammatory stimulus, suggesting the presence of a plateau

Immunity in amyotrophic lateral sclerosis: blurred lines between excessive inflammation and inefficient immune responses

Abstract Despite wide genetic, environmental and clinical heterogeneity in amyotrophic lateral sclerosis, a rapidly fatal neurodegenerative disease targeting motoneurons, neuroinflammation is a common finding. It is marked by local glial activation, T cell infiltration and systemic immune system activation. The immune system has a prominent role in the pathogenesis of various chronic diseases, hence some of them, including some types of cancer, are successfully targeted by immunotherapeutic approaches. However, various anti-inflammatory or immunosuppressive therapies in amyotrophic lateral sclerosis have failed. This prompted increased scrutiny over the immune-mediated processes underlying amyotrophic lateral sclerosis. Perhaps the biggest conundrum is that amyotrophic lateral sclerosis pathogenesis exhibits features of three otherwise distinct immune dysfunctions—excessive inflammation, autoimmunity and inefficient immune responses. Epidemiological and genome-wide association studies show only minimal overlap between amyotrophic lateral sclerosis and autoimmune diseases, so excessive inflammation is usually thought to be secondary to protein aggregation, mitochondrial damage or other stresses. In contrast, several recently characterized amyotrophic lateral sclerosis-linked mutations, including those in TBK1, OPTN, CYLD and C9orf72, could lead to inefficient immune responses and/or damage pile-up, suggesting that an innate immunodeficiency may also be a trigger and/or modifier of this disease. In such cases, non-selective immunosuppression would further restrict neuroprotective immune responses. Here we discuss multiple layers of immune-mediated neuroprotection and neurotoxicity in amyotrophic lateral sclerosis. Particular focus is placed on individual patient mutations that directly or indirectly affect the immune system, and the mechanisms by which these mutations influence disease progression. The topic of immunity in amyotrophic lateral sclerosis is timely and relevant, because it is one of the few common and potentially malleable denominators in this heterogenous disease. Importantly, amyotrophic lateral sclerosis progression has recently been intricately linked to patient T cell and monocyte profiles, as well as polymorphisms in cytokine and chemokine receptors. For this reason, precise patient stratification based on immunophenotyping will be crucial for efficient therapies