Pathogenic myelin-specific antibodies in multiple sclerosis target conformational proteolipid protein 1-anchored membrane domains.

B cell clonal expansion and cerebrospinal fluid (CSF) oligoclonal IgG bands are established features of the immune response in multiple sclerosis (MS). Clone-specific recombinant monoclonal IgG1 Abs (rAbs) derived from MS patient CSF plasmablasts bound to conformational proteolipid protein 1 (PLP1) membrane complexes and, when injected into mouse brain with human complement, recapitulated histologic features of MS pathology: oligodendrocyte cell loss, complement deposition, and CD68+ phagocyte infiltration. Conformational PLP1 membrane epitopes were complex and governed by the local cholesterol and glycolipid microenvironment. Abs against conformational PLP1 membrane complexes targeted multiple surface epitopes, were enriched within the CSF compartment, and were detected in most MS patients, but not in inflammatory and noninflammatory neurologic controls. CSF PLP1 complex Abs provide a pathogenic autoantibody biomarker specific for MS.

Generation and diversification of recombinant monoclonal antibodies.

Antibodies are indispensable tools used for a large number of applications in both foundational and translational bioscience research; however, there are drawbacks to using traditional antibodies generated in animals. These include a lack of standardization leading to problems with reproducibility, high costs of antibodies purchased from commercial sources, and ethical concerns regarding the large number of animals used to generate antibodies. To address these issues, we have developed practical methodologies and tools for generating low-cost, high-yield preparations of recombinant monoclonal antibodies and antibody fragments directed to protein epitopes from primary sequences. We describe these methods here, as well as approaches to diversify monoclonal antibodies, including customization of antibody species specificity, generation of genetically encoded small antibody fragments, and conversion of single chain antibody fragments (e.g. scFv) into full-length, bivalent antibodies. This study focuses on antibodies directed to epitopes important for mitosis and kinetochore function; however, the methods and reagents described here are applicable to antibodies and antibody fragments for use in any field.

Mitochondrial damage in renal epithelial cells is potentiated by protein exposure in propionic aciduria.

Propionic aciduria (PA) is caused by deficiency of the mitochondrial enzyme propionyl-CoA carboxylase (PCC). Due to inefficient propionate catabolism patients are endangered by life-threatening ketoacidotic crisis. Protein and amino acid restriction are major therapeutic pillars. However, long-term complications like neurological deterioration and cardiac abnormalities cannot be prevented. Chronic kidney disease (CKD), which is a well-known characteristic of methylmalonic aciduria two enzymatic steps downstream from PCC, has been recognized as a novel late-onset complication in PA. The pathophysiology of CKD in PA is unclear. We investigated mitochondrial structure and metabolism in human renal tubular cells of healthy controls and PA patients. The cells were exposed to either standard cell culture conditions (NT), high protein (HP) or high concentrations of isoleucine and valine (I/V). Mitochondrial morphology changed to condensed, fractured morphology in PA cells irrespective of the cell culture medium. HP and I/V exposure, however, potentiated oxidative stress in PA cells. Mitochondrial mass was enriched in PA cells, and further increased by HP and I/V exposure suggesting a need for compensation. Alterations in the tricarboxylic acid cycle intermediates and accumulation of medium- and long-chain acylcarnitines pointed to altered mitochondrial energy metabolism. Mitophagy was silenced while autophagy as cellular defense mechanisms was highly active in PA cells. The data demonstrate that PA is associated with renal mitochondrial damage which is aggravated by protein and I/V load. Preservation of mitochondrial energy homeostasis in renal cells may be a potential future therapeutic target.

Defective lysosomal storage in Fabry disease modifies mitochondrial structure, metabolism and turnover in renal epithelial cells.

Fabry disease (FD) is an X-linked lysosomal storage disorder. Deficiency of the lysosomal enzyme alpha-galactosidase (GLA) leads to accumulation of potentially toxic globotriaosylceramide (Gb3) on a multisystem level. Cardiac and cerebrovascular abnormalities as well as progressive renal failure are severe, life-threatening long-term complications. The complete pathophysiology of chronic kidney disease (CKD) in FD and the role of tubular involvement for its progression are unclear. We established human renal tubular epithelial cell lines from the urine of male FD patients and male controls. The renal tubular system is rich in mitochondria and involved in transport processes at high-energy costs. Our studies revealed fragmented mitochondria with disrupted cristae structure in FD patient cells. Oxidative stress levels were elevated and oxidative phosphorylation was upregulated in FD pointing at enhanced energetic needs. Mitochondrial homeostasis and energy metabolism revealed major changes as evidenced by differences in mitochondrial number, energy production and fuel consumption. The changes were accompanied by activation of the autophagy machinery in FD. Sirtuin1, an important sensor of (renal) metabolic stress and modifier of different defense pathways, was highly expressed in FD. Our data show that lysosomal FD impairs mitochondrial function and results in severe disturbance of mitochondrial energy metabolism in renal cells. This insight on a tissue-specific level points to new therapeutic targets which might enhance treatment efficacy.

Clinical Features and Outcomes of Pediatric Monophasic and Recurrent Idiopathic Optic Neuritis.

Limited data exist on isolated optic neuritis in children. We report the clinical features and treatment of pediatric subjects with monophasic and recurrent idiopathic optic neuritis. This retrospective cohort study of patients with isolated optic neuritis identified 10 monophasic and 7 recurrent optic neuritis cases. Monophasic optic neuritis patients were older (mean 13.3 ± 4.22) than those with recurrent idiopathic optic neuritis (9.86 ± 3.63). Females represented 50% of monophasic and 85.7% of recurrent idiopathic optic neuritis cases. Patients with monophasic optic neuritis were less likely to have a bilateral onset than recurrent idiopathic optic neuritis (40% vs 57.1%). Only 1 case had oligoclonal bands in the cerebrospinal fluid CSF. Most recurrent idiopathic optic neuritis cases had evidence of anti-myelin oligodendrocyte glycoprotein (MOG) antibodies (5/7). Treatment of recurrent idiopathic optic neuritis cases included intravenous pulse glucocorticosteroids and immunotherapy. We observed differences between recurrent and monophasic idiopathic optic neuritis. Immunosuppression appeared to prevent further relapses in recurrent idiopathic optic neuritis patients. Weaning immunotherapies after several years of quiescence in recurrent idiopathic optic neuritis may be possible, but larger studies are needed.

Intravascular injections of adenoassociated viral vector serotypes rh10 and PHP.B transduce murine sciatic nerve axons.

Adenoassociated viral vectors provide a safe and robust method for expression of transgenes in nondividing cells such as neurons. Intravenous injections of these vectors provide a means of transducing motoneurons of peripheral nerves. Previous research has demonstrated that serotypes 1, rh10 and PHP.B can transduce motor neuron cell bodies in the spinal cord, but has not quantified expression in the peripheral nerve axon. Axonal labeling is crucial for optogenetic stimulation and detection of action potentials in peripheral nerve. Therefore, in this study, serotypes 1, PHP.B, and rh10 were tested for their ability to label axons of the murine sciatic and tibial nerve following intravenous injection. Serotype rh10 elicits expression in 10% of acetylcholine transferase positive axons of the sciatic nerve in immunohistochemically-stained sections. Serotype rh10 transduces a variety of axon diameters from <1-12 µm, while PHP.B transduces larger axons of diameter (4-16 µm). Expression was not seen with serotype 1. These results show the potential of serotypes PHP.B and rh10 delivery of transgenic products to axons of the peripheral nerve.

Membrane assembly of aquaporin-4 autoantibodies regulates classical complement activation in neuromyelitis optica.

Neuromyelitis optica (NMO) is an autoimmune CNS disorder mediated by pathogenic aquaporin-4 (AQP4) water channel autoantibodies (AQP4-IgG). Although AQP4-IgG-driven complement-dependent cytotoxicity (CDC) is critical for the formation of NMO lesions, the molecular mechanisms governing optimal classical pathway activation are unknown. We investigated the molecular determinants driving CDC in NMO using recombinant AQP4-specific autoantibodies (AQP4 rAbs) derived from affected patients. We identified a group of AQP4 rAbs targeting a distinct extracellular loop C epitope that demonstrated enhanced CDC on target cells. Targeted mutations of AQP4 rAb Fc domains that enhance or diminish C1q binding or antibody Fc-Fc interactions showed that optimal CDC was driven by the assembly of multimeric rAb platforms that increase multivalent C1q binding and facilitate C1q activation. A peptide that blocks antibody Fc-Fc interaction inhibited CDC induced by AQP4 rAbs and polyclonal NMO patient sera. Super-resolution microscopy revealed that AQP4 rAbs with enhanced CDC preferentially formed organized clusters on supramolecular AQP4 orthogonal arrays, linking epitope-dependent multimeric assembly with enhanced C1q binding and activation. The resulting model of AQP4-IgG CDC provides a framework for understanding classical complement activation in human autoantibody-mediated disorders and identifies a potential new therapeutic avenue for treating NMO.

Glucose-regulated protein 78 autoantibody associates with blood-brain barrier disruption in neuromyelitis optica.

Neuromyelitis optica (NMO) is an inflammatory disorder mediated by antibodies to aquaporin-4 (AQP4) with prominent blood-brain barrier (BBB) breakdown in the acute phase of the disease. Anti-AQP4 antibodies are produced mainly in the periphery, yet they target the astrocyte perivascular end feet behind the BBB. We reasoned that an endothelial cell-targeted autoantibody might promote BBB transit of AQP4 antibodies and facilitate NMO attacks. Using monoclonal recombinant antibodies (rAbs) from patients with NMO, we identified two that strongly bound to the brain microvascular endothelial cells (BMECs). Exposure of BMECs to these rAbs resulted in nuclear translocation of nuclear factor κB p65, decreased claudin-5 protein expression, and enhanced transit of macromolecules. Unbiased membrane proteomics identified glucose-regulated protein 78 (GRP78) as the rAb target. Using immobilized GRP78 to deplete GRP78 antibodies from pooled total immunoglobulin G (IgG) of 50 NMO patients (NMO-IgG) reduced the biological effect of NMO-IgG on BMECs. GRP78 was expressed on the surface of murine BMECs in vivo, and repeated administration of a GRP78-specific rAb caused extravasation of serum albumin, IgG, and fibrinogen into mouse brains. Our results identify GRP78 antibodies as a potential component of NMO pathogenesis and GRP78 as a candidate target for promoting central nervous system transit of therapeutic antibodies.

Mutagenesis of the aquaporin 4 extracellular domains defines restricted binding patterns of pathogenic neuromyelitis optica IgG.

Neuromyelitis optica-immunoglobulin G (NMO-IgG) binds to aquaporin-4 (AQP4) water channels in the central nervous system leading to immune-mediated injury. We have previously demonstrated that a high proportion of CSF plasma cells of NMO patients produce antibody to the extracellular domains of the AQP4 protein and that recombinant IgG (rAb) derived from these cells recapitulate pathogenic features of disease. We performed a comprehensive mutational analysis of the three extracellular loops of the M23 isoform of human AQP4 using both serial and single point mutations, and we evaluated the effects on binding of NMO AQP4-reactive rAbs by quantitative immunofluorescence. Whereas all NMO rAbs required conserved loop C ((137)TP(138) and Val(150)) and loop E ((230)HW(231)) amino acids for binding, two broad patterns of NMO-IgG recognition could be distinguished based on differential sensitivity to loop A amino acid changes. Pattern 1 NMO rAbs were insensitive to loop A mutations and could be further discriminated by differential sensitivity to amino acid changes in loop C ((148)TM(149) and His(151)) and loop E (Asn(226) and Glu(228)). Alternatively, pattern 2 NMO rAbs showed significantly reduced binding following amino acid changes in loop A ((63)EKP(65) and Asp(69)) and loop C (Val(141), His(151), and Leu(154)). Amino acid substitutions at (137)TP(138) altered loop C conformation and abolished the binding of all NMO rAbs and NMO-IgG, indicating the global importance of loop C conformation to the recognition of AQP4 by pathogenic NMO Abs. The generation of human NMO rAbs has allowed the first high resolution mapping of extracellular loop amino acids critical for NMO-IgG binding and identified regions of AQP4 extracellular structure that may represent prime targets for drug therapy.

Neuroserpin up-regulation in the Alzheimer's disease brain is associated with elevated thyroid hormone receptor-ß1 and HuD expression.

Neuroserpin, the major inhibitor of tissue plasminogen activator (tPA) in brain, has been shown to be up-regulated in Alzheimer's disease (AD). Inhibition of tPA activity leads to reduced brain levels of plasmin, one of the main enzymes responsible for the degradation and clearance of amyloid-beta and its plaques from the brain. Thyroid hormone is one of the few factors known to enhance expression of neuroserpin in neurons. Thyroid hormone acts on neurons by binding to its receptors THR1α and THR1ß, which then function in the nucleus to up-regulate the expression of numerous genes including the RNA-binding protein HuD. HuD acts post-transcriptionally to enhance expression of numerous proteins including neuroserpin by stabilizing their mRNAs. A series of Alzheimer's disease brain tissues were compared to age-matched control brains for their expression of neuroserpin, THRß1 and HuD by western blotting. Alzheimer's disease brain tissues with elevated neuroserpin protein also showed increased expression of THRß1 and HuD. Pair-wise analyses showed significant correlation p-values between neuroserpin, THRß1 and HuD levels; suggesting that the up-regulation of neuroserpin in Alzheimer's disease brain may result from an activation of the thyroid hormone response system in these individuals. These findings provide evidence for a potential relationship between thyroid hormone disorders and Alzheimer's disease.

Amyloid-beta levels are significantly reduced and spatial memory defects are rescued in a novel neuroserpin-deficient Alzheimer's disease transgenic mouse model.

Amyloid-beta (Aß) plaques are a hallmark of Alzheimer's disease. Several proteases including plasmin are thought to promote proteolytic cleavage and clearance of Aß from brain. The activity of both plasmin and tissue plasminogen activator are reduced in Alzheimer's disease brain, while the tissue plasminogen activator inhibitor neuroserpin is up-regulated. Here, the relationship of tissue plasminogen activator and neuroserpin to Aß levels is explored in mouse models. Aß(1-42) peptide injected into the frontal cortex of tissue plasminogen activator knockout mice is slow to disappear compared to wildtype mice, whereas neuroserpin knockout mice show a rapid clearance of Aß(1-42). The relationship of neuroserpin and tissue plasminogen activator to Aß plaque formation was studied further by knocking-out neuroserpin in the human amyloid precursor protein-J20 transgenic mouse. Compared to the J20-transgenic mouse, the neuroserpin-deficient J20-transgenic mice have a dramatic reduction of Aß peptides, fewer and smaller plaques, and more active tissue plasminogen activator associated with plaques. Furthermore, neuroserpin-deficient J20-transgenic mice have near normal performances in the Morris water maze, in contrast to the spatial memory defects seen in J20-transgenic mice. These results support the concept that neuroserpin inhibition of tissue plasminogen activator plays an important role both in the accumulation of brain amyloid plaques and loss of cognitive abilities.

Plasminogen activator promotes recovery following spinal cord injury.

Plasminogen activators play an important role in synaptic plasticity associated with the crossed phrenic phenomenon (CPP) and recovery of respiratory function after spinal cord injury. A genetic approach using knockout mice lacking various genes in the plasminogen activator/plasmin system has shown that induction of urokinase plasminogen activator (uPA) is required during the first hour after a C2-hemisection for the acquisition of the CPP response. The uPA knockout mice do not show the structural remodeling of phrenic motor neuron synapses characteristic of the CPP response. As shown here uPA acts in a cell signaling manner via binding to its receptor uPAR rather than as a protease, since uPAR knockout mice or knock-in mice possessing a modified uPA that is unable to bind to uPAR both fail to generate a CPP and recover respiratory function. Microarray data and real-time PCR analysis of mRNAs induced in the phrenic motor nucleus after C2-hemisection in C57Bl/6 mice as compared to uPA knockout mice indicate a potential cell signaling cascade downstream possibly involving ß-integrin and Src, and other pathways. Identification of these uPA-mediated signaling pathways may provide the opportunity to pharmacologically upregulate the synaptic plasticity necessary for recovery of phrenic motoneuron activity following cervical spinal cord injury.

APP and APLP2 are essential at PNS and CNS synapses for transmission, spatial learning and LTP.

Despite its key role in Alzheimer pathogenesis, the physiological function(s) of the amyloid precursor protein (APP) and its proteolytic fragments are still poorly understood. Previously, we generated APPsα knock-in (KI) mice expressing solely the secreted ectodomain APPsα. Here, we generated double mutants (APPsα-DM) by crossing APPsα-KI mice onto an APLP2-deficient background and show that APPsα rescues the postnatal lethality of the majority of APP/APLP2 double knockout mice. Surviving APPsα-DM mice exhibited impaired neuromuscular transmission, with reductions in quantal content, readily releasable pool, and ability to sustain vesicle release that resulted in muscular weakness. We show that these defects may be due to loss of an APP/Mint2/Munc18 complex. Moreover, APPsα-DM muscle showed fragmented post-synaptic specializations, suggesting impaired postnatal synaptic maturation and/or maintenance. Despite normal CNS morphology and unaltered basal synaptic transmission, young APPsα-DM mice already showed pronounced hippocampal dysfunction, impaired spatial learning and a deficit in LTP that could be rescued by GABA(A) receptor inhibition. Collectively, our data show that APLP2 and APP are synergistically required to mediate neuromuscular transmission, spatial learning and synaptic plasticity.

Expression and distribution of voltage-gated sodium channels in the cerebellum.

In order to understand the effects of sodium channels on synaptic signaling and response in the cerebellum, it is essential to know for each class of neuron what sodium channel isoforms are present, and the properties and distribution of each. Sodium channels are heteromultimeric membrane proteins, consisting of a large alpha subunit that forms the pore, and one or more beta subunits. Ten genes encode an alpha subunit in mammals, and of these, four are expressed in the cerebellum: Nav1.1, Nav1.2, Nav1.3 and Nav1.6. Three genes encode beta subunits (Nabeta1-3), and all three are expressed in the cerebellum. However, Nav1.3 and Nabeta3 have been found only in the developing cerebellum. All sodium channels recorded in the cerebellum are TTX-sensitive with similar kinetics, making it difficult to identify the isoforms electrically. Thus, most of the expression studies have relied on techniques that allow visualization of sodium channel subtypes at the level of mRNA and protein. In situ hybridization and immunolocalization studies demonstrated that granule cells predominantly express Nav1.2, Nav1.6, Nabeta1, and Nabeta2. Protein for Nav1.2 and Nav1.6 is localized primarily in granule cell parallel fibers. Purkinje cells express Nav1.1, Nav1.6, Nabeta1 and Nabeta2. The somato-dendritic localization of Nav1.1 and Nav1.6 in Purkinje cells suggests that these isoforms are involved in the integration of synaptic input. Deep cerebellar nuclei neurons expressed Nav1.1 and Nav1.6 as well as Nabeta1. Bergmann glia expressed Nav1.6, but not granule cell layer astrocytes. Some sodium channel isoforms that are not expressed normally in the adult cerebellum are expressed in animals with mutations or disease. Electrophysiological studies suggest that Nav1.6 is responsible for spontaneous firing and bursting features in Purkinje cells, but the specialized functions of the other subunits in the cerebellum remain unknown.