Tissue distribution of 35S-metabolically labeled neublastin (BG00010) in rats.

Neublastin (NBN) is a neurotrophic growth factor that promotes the survival and regenerative properties of nociceptive neurons and has been tested in clinical trials as a treatment for neuropathic pain in individuals with sciatica and painful lumbosacral radiculopathy. Like many low molecular weight heparin binding proteins, NBN is rapidly cleared from the blood following systemic administration. To explore ADME properties of NBN in rats, we used metabolically 35S-labeled NBN following IV and SC administration quantifying counts and intact protein in kidney, liver, brain, serum, and urine at 5 min, 8 h, 24 h and 48 h, and biodistribution in whole body carcasses by QWBA at 2, 8, 48, 96, and 168 h post dose. NBN is rapidly taken up by tissues mainly by liver and kidney and then degraded. Products of degradation are excreted in urine or recycled and utilized for resynthesis. The data we generated for NBN provides a first look at the complex clearance mechanisms for this protein and should aid in the design of ADME studies for other heparin binding proteins.

Randomized phase I clinical trial of anti-α-synuclein antibody BIIB054.

BACKGROUND: Pathological and genetic evidence implicates toxic effects of aggregated α-synuclein in the pathophysiology of neuronal dysfunction and degeneration in Parkinson's disease. Immunotherapy targeting aggregated α-synuclein is a promising strategy for delaying disease progression. OBJECTIVE: This study (NCT02459886) evaluated the safety, tolerability, and pharmacokinetics of BIIB054, a human-derived monoclonal antibody that preferentially binds to aggregated α-synuclein, in healthy volunteers and participants with Parkinson's disease. METHODS: A total of 48 healthy volunteers (age 40-65, 19 women) and 18 Parkinson's disease participants (age 47-75, 5 women, Hoehn and Yahr stage ≤2.5) were in the study. Volunteers were enrolled into 6 single-dose cohorts of BIIB054 (range 1-135 mg/kg) or placebo, administered intravenously; Parkinson's disease participants received a single dose of BIIB054 (15 or 45 mg/kg) or placebo. All participants were evaluated for 16 weeks with clinical, neuroimaging, electrocardiogram, and laboratory assessments. Serum and cerebrospinal fluid BIIB054 concentrations were measured. BIIB054/α-synuclein complexes were measured in plasma. RESULTS: Most adverse events were mild and assessed by investigators as unrelated to the study drug. Pharmacokinetic parameters for volunteers and the Parkinson's disease participants were similar. BIIB054 serum exposure and maximum concentrations were dose proportional during the dose range studied. In volunteers and the Parkinson's disease participants, the serum half-life of BIIB054 was 28 to 35 days; the cerebrospinal fluid-to-serum ratio ranged from 0.13% to 0.56%. The presence of BIIB054/α-synuclein complexes in plasma was confirmed; all Parkinson's disease participants showed almost complete saturation of the BIIB054/α-synuclein complex formation. CONCLUSIONS: BIIB054 has favorable safety, tolerability, and pharmacokinetic profiles in volunteers and Parkinson's disease participants, supporting further clinical development. © 2019 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.

A Prodomain Fragment from the Proteolytic Activation of Growth Differentiation Factor 11 Remains Associated with the Mature Growth Factor and Keeps It Soluble.

Growth differentiation factor 11 (GDF11), a member of the transforming growth factor ß (TGF-ß) family, plays diverse roles in mammalian development. It is synthesized as a large, inactive precursor protein containing a prodomain, pro-GDF11, and exists as a homodimer. Activation requires two proteolytic processing steps that release the prodomains and transform latent pro-GDF11 into active mature GDF11. In studying proteolytic activation in vitro, we discovered that a 6-kDa prodomain peptide containing residues 60-114, PDP60-114, remained associated with the mature growth factor. Whereas the full-length prodomain of GDF11 is a functional antagonist, PDP60-114 had no impact on activity. The specific activity of the GDF11/PDP60-114 complex (EC50 = 1 nM) in a SMAD2/3 reporter assay was identical to that of mature GDF11 alone. PDP60-114 improved the solubility of mature GDF11 at neutral pH. As the growth factor normally aggregates/precipitates at neutral pH, PDP60-114 can be used as a solubility-enhancing formulation. Expression of two engineered constructs with PDP60-114 genetically fused to the mature domain of GDF11 through a 2x or 3x G4S linker produced soluble monomeric products that could be dimerized through redox reactions. The construct with a 3x G4S linker retained 10% activity (EC50 = 10 nM), whereas the construct connected with a 2x G4S linker could only be activated (EC50 = 2 nM) by protease treatment. Complex formation with PDP60-114 represents a new strategy for stabilizing GDF11 in an active state that may translate to other members of the TGF-ß family that form latent pro/mature domain complexes.

LINGO-1 Regulates Oligodendrocyte Differentiation through the Cytoplasmic Gelsolin Signaling Pathway.

Differentiation and maturation of oligodendrocyte progenitor cells (OPCs) involve the assembly and disassembly of actin microfilaments. However, how actin dynamics are regulated during this process remains poorly understood. Leucine-rich repeat and Ig-like domain-containing Nogo receptor interacting protein 1 (LINGO-1) is a negative regulator of OPC differentiation. We discovered that anti-LINGO-1 antibody-promoted OPC differentiation was accompanied by upregulation of cytoplasmic gelsolin (cGSN), an abundant actin-severing protein involved in the depolymerization of actin filaments. Treating rat OPCs with cGSN siRNA reduced OPC differentiation, whereas overexpression of cGSN promoted OPC differentiation in vitro and remyelination in vivo Furthermore, coexpression of cGSN and LINGO-1 blocked the inhibitory effect of LINGO-1. Our study demonstrates that cGSN works downstream of LINGO-1 signaling pathway, which enhances actin dynamics and is essential for OPC morphogenesis and differentiation. This finding may lead to novel therapeutic approaches for the treatment of demyelinating diseases such as multiple sclerosis (MS).SIGNIFICANCE STATEMENT Myelin loss and subsequent axon degeneration contributes to a variety of neurological diseases, such as multiple sclerosis (MS). Understanding the regulation of myelination by oligodendrocytes is therefore critical for developing therapies for the treatment of MS. We previously demonstrated that leucine-rich repeat and Ig-like domain-containing Nogo receptor interacting protein 1 (LINGO-1) is a negative regulator of oligodendrocyte differentiation and that anti-LINGO-1 promotes remyelination in preclinical animal models for MS and in a phase II acute optic neuritis clinical trial (RENEW). The mechanism by which LINGO-1 regulates oligodendrocyte differentiation is unknown. Here, we demonstrate that LINGO-1 regulates oligodendrocyte differentiation and maturation through the cytoplasmic gelsolin signaling pathway, providing new drug targets for the treatment of demyelination diseases.

Engineering potent long-acting variants of the Wnt inhibitor DKK2.

Wnt signaling pathways are required for a wide variety of biological processes ranging from embryonic development to tissue repair and regeneration. Dickkopf-2 (DKK2) is classically defined as a canonical Wnt inhibitor, though it may play a role in activating non-canonical Wnt pathways in the context of endothelial network formation after acute injury. Here we report the discovery of a fusion partner for a DKK2 polypeptide that significantly improves the expression, biochemical properties and pharmacokinetics (PK) of the DKK2 polypeptide. Specifically, human serum albumin (HSA) was identified as a highly effective fusion partner. Substitution of selected amino acid residues in DKK2 designed to decrease heparan sulfate binding by HSA-DKK2 variants, further improved the PK properties of the molecule in rodents. The HSA-DKK2 variants were monomeric, as thermally stable as wild type, and active as measured by their ability to bind to and prevent phosphorylation of the Wnt coreceptor LRP6. Our engineering efforts resulted in potent long-lived variants of the canonical Wnt inhibitor DKK2, applicable for Wnt pathway manipulation either by systematic delivery or focused administration at sites of tissue injury.

Investigating the Role of Artemin Glycosylation.

PURPOSE: Oligosaccharides play diverse and unpredictable functional roles when attached to proteins and are a largely unexplored scaffold for deconstructing and attributing novel functions to proteins during drug development. Here, the glycoprotein Artemin (ART) was carefully assessed by multiple analytical methods that allow us to provide a comprehensive understanding of how N-linked glycosylation impact the structural and functional properties of ART. METHODS: Modification of the N-linked glycan of ART was performed by incubation with various enzymes. Biological assays and systems were used to examine the relative activity and pharmacokinetic properties of ART as a function of glycosylation. In order to reveal the conformational impact of glycosylation on ART, hydrogen/deuterium exchange mass spectrometry (HDX-MS) was employed in addition to differential scanning calorimetry. The colloidal stability of ART glycovariants was assessed by dynamic light scattering, viscometry, and solubility assays. RESULTS: No difference in pharmacokinetics or relative potency was revealed between glycosylated and nonglycosylated ART. Surprisingly, the HDX-MS data indicated that the glycan does not greatly influence the conformation and dynamics of the protein. In contrast, differences in thermal and colloidal stability clearly revealed a role of glycosylation in increasing the solubility and stability of ART. CONCLUSIONS: Our findings demonstrate how careful analysis using multiple advanced techniques can be used to identify and dissect the multiple potential functions of protein glycosylation and form a prerequisite for glycoengineering and drug development of glycoproteins.

Blocking LINGO-1 in vivo reduces degeneration and enhances regeneration of the optic nerve.

BACKGROUND: Two ongoing phase II clinical trials (RENEW and SYNERGY) have been developed to test the efficacy of anti-LINGO-1 antibodies in acute optic neuritis and relapsing forms of multiple sclerosis, respectively. Across a range of experimental models, LINGO-1 has been found to inhibit neuron and oligodendrocyte survival, axon regeneration, and (re)myelination. The therapeutic effects of anti-LINGO-1 antibodies on optic nerve axonal loss and regeneration have not yet been investigated. OBJECTIVE: In this series of studies we investigate if LINGO-1 antibodies can prevent acute inflammatory axonal loss, and promote axonal regeneration after injury in rodent optic nerves. METHODS: The effects of anti-LINGO-1 antibody on optic nerve axonal damage were assessed using rodent myelin oligodendrocyte glycoprotein experimental autoimmune encephalomyelitis (EAE), and its effects on axonal regeneration were assessed in optic nerve crush injury models. RESULTS: In the optic nerve, anti-LINGO-1 antibody therapy was associated with improved optic nerve parallel diffusivity measures on MRI in mice with EAE and reduced axonal loss in rat EAE. Both anti-LINGO-1 antibody therapy and the genetic deletion of LINGO-1 reduced nerve crush-induced axonal degeneration and enhanced axonal regeneration. CONCLUSION: These data demonstrate that LINGO-1 blockade is associated with axonal protection and regeneration in the injured optic nerve.

Artemin promotes functional long-distance axonal regeneration to the brainstem after dorsal root crush.

Recovery after a spinal cord injury often requires that axons restore synaptic connectivity with denervated targets several centimeters from the site of injury. Here we report that systemic artemin (ARTN) treatment promotes the regeneration of sensory axons to the brainstem after brachial dorsal root crush in adult rats. ARTN not only stimulates robust regeneration of large, myelinated sensory axons to the brainstem, but also promotes functional reinnervation of the appropriate target region, the cuneate nucleus. ARTN signals primarily through the RET tyrosine kinase, an interaction that requires the nonsignaling coreceptor GDNF family receptor (GFRα3). Previous studies reported limited GFRα3 expression on large sensory neurons, but our findings demonstrate that ARTN promotes robust regeneration of large, myelinated sensory afferents. Using a cell sorting technique, we demonstrate that GFRα3 expression is similar in myelinated and unmyelinated adult sensory neurons, suggesting that ARTN likely induces long-distance regeneration by binding GFRα3 and RET. Although ARTN is delivered for just 2 wk, regeneration to the brainstem requires more than 3 mo, suggesting that brief trophic support may initiate intrinsic growth programs that remain active until targets are reached. Given its ability to promote targeted functional regeneration to the brainstem, ARTN may represent a promising therapy for restoring sensory function after spinal cord injury.

Inhibition of LINGO-1 promotes functional recovery after experimental spinal cord demyelination.

Blocking LINGO-1 has been shown to enhance remyelination in the rat lysolecithin-induced focal spinal cord demyelination model. We used transcranial magnetic motor-evoked potentials (tcMMEPs) to assess the effect of blocking LINGO-1 on recovery of axonal function in a mouse lysolecithin model at 1, 2 and 4weeks after injury. The role of LINGO-1 was assessed using LINGO-1 knockout (KO) mice and in wild-type mice after intraperitoneal administration of anti-LINGO-1 antagonist monoclonal antibody (mAb3B5). Response rates (at 2 and 4weeks) and amplitudes (at 4weeks) were significantly increased in LINGO-1 KO and mAb3B5-treated mice compared with matched controls. The latency of potentials at 4weeks was significantly shorter in mAb3B5-treated mice compared with controls. Lesion areas in LINGO-1 KO and mAb3B5-treated mice were reduced significantly compared with matched controls. The number of remyelinated axons within the lesions was increased and the G-ratios of the axons were decreased in both LINGO-1 KO and mAb3B5-treated mice compared with matched controls. These data provide morphometric and functional evidence of enhancement of remyelination associated with antagonism of LINGO-1.

A novel platform for engineering blood-brain barrier-crossing bispecific biologics.

The blood-brain barrier (BBB) prevents the access of therapeutic antibodies to central nervous system (CNS) targets. The engineering of bispecific antibodies in which a therapeutic "arm" is combined with a BBB-transcytosing arm can significantly enhance their brain delivery. The BBB-permeable single-domain antibody FC5 was previously isolated by phenotypic panning of a naive llama single-domain antibody phage display library. In this study, FC5 was engineered as a mono- and bivalent fusion with the human Fc domain to optimize it as a modular brain delivery platform. In vitro studies demonstrated that the bivalent fusion of FC5 with Fc increased the rate of transcytosis (Papp) across brain endothelial monolayer by 25% compared with monovalent fusion. Up to a 30-fold enhanced apparent brain exposure (derived from serum and cerebrospinal fluid pharmacokinetic profiles) of FC5- compared with control domain antibody-Fc fusions after systemic dosing in rats was observed. Systemic pharmacological potency was evaluated in the Hargreaves model of inflammatory pain using the BBB-impermeable neuropeptides dalargin and neuropeptide Y chemically conjugated with FC5-Fc fusion proteins. Improved serum pharmacokinetics of Fc-fused FC5 contributed to a 60-fold increase in pharmacological potency compared with the single-domain version of FC5; bivalent and monovalent FC5 fusions with Fc exhibited similar systemic pharmacological potency. The study demonstrates that modular incorporation of FC5 as the BBB-carrier arm in bispecific antibodies or antibody-drug conjugates offers an avenue to develop pharmacologically active biotherapeutics for CNS indications.

LINGO-1 regulates oligodendrocyte differentiation by inhibiting ErbB2 translocation and activation in lipid rafts.

Oligodendrocyte differentiation is negatively regulated by LINGO-1 and positively regulated by the ErbB2 receptor tyrosine kinase. In wild-type oligodendrocytes, inhibition of ErbB2 blocks differentiation, whereas activation of ErbB2 promotes differentiation. In LINGO-1(-/-) oligodendrocytes, inhibition of ErbB2 blocks oligodendrocyte differentiation; whereas activation of ErbB2 does not enhance differentiation. Biological and biochemical evidence showing that LINGO-1 can directly bind to ErbB2, block ErbB2 translocation into lipid rafts, and inhibit its phosphorylation for activation. The study demonstrates a novel regulatory mechanism of ErbB2 function whereby LINGO-1 suppresses oligodendrocyte differentiation by inhibiting ErbB2 translocation and activation in lipid rafts.

Meteorin reverses hypersensitivity in rat models of neuropathic pain.

Neuropathic pain is caused by a lesion or disease to the somatosensory nervous system and current treatment merely reduces symptoms. Here, we investigate the potential therapeutic effect of the neurotrophic factor Meteorin on multiple signs of neuropathic pain in two distinct rat models. In a first study, two weeks of intermittent systemic administration of recombinant Meteorin led to a dose-dependent reversal of established mechanical and cold hypersensitivity in rats after photochemically-induced sciatic nerve injury. Moreover, analgesic efficacy lasted for at least one week after treatment cessation. In rats with a chronic constriction injury (CCI) of the sciatic nerve, five systemic injections of Meteorin over 9 days dose-dependently reversed established mechanical and thermal hypersensitivity as well as weight bearing deficits taken as a surrogate marker of spontaneous pain. The beneficial effects of systemic Meteorin were sustained for at least three weeks after treatment ended and no adverse side effects were observed. Pharmacokinetic analysis indicated that plasma Meteorin exposure correlated well with dosing and was no longer detectable after 24 hours. This pharmacokinetic profile combined with a delayed time of onset and prolonged duration of analgesic efficacy on multiple parameters suggests a disease-modifying mechanism rather than symptomatic pain relief. In sciatic nerve lesioned rats, delivery of recombinant Meteorin by intrathecal injection was also efficacious in reversing mechanical and cold hypersensitivity. Together, these data demonstrate that Meteorin represents a novel treatment strategy for the effective and long lasting relief from the debilitating consequences of neuropathic pain.

Oligodendrocyte differentiation and myelination defects in OMgp null mice.

OMgp is selectively expressed in CNS by oligodendrocyte. However, its potential role(s) in oligodendrocyte development and myelination remain unclear. We show that OMgp null mice are hypomyelinated in their spinal cords, resulting in slower ascending and descending conduction velocities compared to wild-type mice. Consistent with the hypomyelination, in the MOG induced EAE model, OMgp null mice show a more severe EAE clinical disease and slower nerve conduction velocity compared to WT animals. The contribution of OMgp to oligodendrocyte differentiation and myelination was verified using cultured oligodendrocytes from null mice. Oligodendrocytes isolated from OMgp null mice show a significant decrease in the number of MBP(+) cells and in myelination compared to wild-type mice. The dramatic effects of the OMgp KO in oligodendrocyte maturation in vivo and in vitro reveal a new and important function for OMgp in regulating CNS myelination.

Promotion of central nervous system remyelination by induced differentiation of oligodendrocyte precursor cells.

OBJECTIVE: Repair of demyelinated axons in diseases such as multiple sclerosis requires activation of the myelination program in existing or newly recruited oligodendrocyte precursor cells (OPCs). The control of OPC differentiation and initiation of myelination during repair is poorly understood. In this study, we test the ability of anti-LINGO-1 reagents to promote myelination in vitro and remyelination in the rodent adult central nervous system in vivo. METHODS: The effects of LINGO-1 antagonists on the differentiation of OPCs and the promotion of myelination has been assayed using a combination of coculture and slice culture preparations. Using three different animal models of demyelination and remyelination, we morphologically and functionally assessed the effects of LINGO-1 antagonists on OPC differentiation and myelin repair. RESULTS: The data indicate that in vitro treatment with antagonists of LINGO-1 promote OPC differentiation and myelination, whereas in vivo remyelination is accelerated in lysophosphatidylcholine- or cuprizone-induced demyelination. This remyelination is associated with enhanced OPC differentiation and functional recovery of conduction velocities in demyelinated axons. INTERPRETATION: Our studies demonstrate that LINGO-1 antagonism promotes OPC differentiation and remyelination, and suggest LINGO-1 functions as an inhibitor of OPC differentiation to retard central nervous system remyelination.

LINGO-1 antagonist promotes spinal cord remyelination and axonal integrity in MOG-induced experimental autoimmune encephalomyelitis.

Demyelinating diseases, such as multiple sclerosis, are characterized by the loss of the myelin sheath around neurons, owing to inflammation and gliosis in the central nervous system (CNS). Current treatments therefore target anti-inflammatory mechanisms to impede or slow disease progression. The identification of a means to enhance axon myelination would present new therapeutic approaches to inhibit and possibly reverse disease progression. Previously, LRR and Ig domain-containing, Nogo receptor-interacting protein (LINGO-1) has been identified as an in vitro and in vivo negative regulator of oligodendrocyte differentiation and myelination. Here we show that loss of LINGO-1 function by Lingo1 gene knockout or by treatment with an antibody antagonist of LINGO-1 function leads to functional recovery from experimental autoimmune encephalomyelitis. This is reflected biologically by improved axonal integrity, as confirmed by magnetic resonance diffusion tensor imaging, and by newly formed myelin sheaths, as determined by electron microscopy. Antagonism of LINGO-1 or its pathway is therefore a promising approach for the treatment of demyelinating diseases of the CNS.

Inhibition of the leucine-rich repeat protein LINGO-1 enhances survival, structure, and function of dopaminergic neurons in Parkinson's disease models.

The nervous system-specific leucine-rich repeat Ig-containing protein LINGO-1 is associated with the Nogo-66 receptor complex and is endowed with a canonical EGF receptor (EGFR)-like tyrosine phosphorylation site. Our studies indicate that LINGO-1 expression is elevated in the substantia nigra of Parkinson's disease (PD) patients compared with age-matched controls and in animal models of PD after neurotoxic lesions. LINGO-1 expression is present in midbrain dopaminergic (DA) neurons in the human and rodent brain. Therefore, the role of LINGO-1 in cell damage responses of DA neurons was examined in vitro and in experimental models of PD induced by either oxidative (6-hydroxydopamine) or mitochondrial (N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) toxicity. In LINGO-1 knockout mice, DA neuron survival was increased and behavioral abnormalities were reduced compared with WT. This neuroprotection was accompanied by increased Akt phosphorylation (p-Akt). Similar neuroprotective in vivo effects on midbrain DA neurons were obtained in WT mice by blocking LINGO-1 activity using LINGO-1-Fc protein. Neuroprotection and enhanced neurite growth were also demonstrated for midbrain DA neurons in vitro. LINGO-1 antagonists (LINGO-1-Fc, dominant negative LINGO-1, and anti-LINGO-1 antibody) improved DA neuron survival in response to MPP+ in part by mechanisms that involve activation of the EGFR/Akt signaling pathway through a direct inhibition of LINGO-1's binding to EGFR. These results show that inhibitory agents of LINGO-1 activity can protect DA neurons against degeneration and indicate a role for the leucine-rich repeat protein LINGO-1 and related classes of proteins in the pathophysiological responses of midbrain DA neurons in PD.

Artemin crystal structure reveals insights into heparan sulfate binding.

Artemin (ART) promotes the growth of developing peripheral neurons by signaling through a multicomponent receptor complex comprised of a transmembrane tyrosine kinase receptor (cRET) and a specific glycosylphosphatidylinositol-linked co-receptor (GFRalpha3). Glial cell line-derived neurotrophic factor (GDNF) signals through a similar ternary complex but requires heparan sulfate proteoglycans (HSPGs) for full activity. HSPG has not been demonstrated as a requirement for ART signaling. We crystallized ART in the presence of sulfate and solved its structure by isomorphous replacement. The structure reveals ordered sulfate anions bound to arginine residues in the pre-helix and amino-terminal regions that were organized in a triad arrangement characteristic of heparan sulfate. Three residues in the pre-helix were singly or triply substituted with glutamic acid, and the resulting proteins were shown to have reduced heparin-binding affinity that is partly reflected in their ability to activate cRET. This study suggests that ART binds HSPGs and identifies residues that may be involved in HSPG binding.

Blockade of Nogo-66, myelin-associated glycoprotein, and oligodendrocyte myelin glycoprotein by soluble Nogo-66 receptor promotes axonal sprouting and recovery after spinal injury.

The growth of injured axons in the adult mammalian CNS is limited after injury. Three myelin proteins, Nogo, MAG (myelin-associated glycoprotein), and OMgp (oligodendrocyte myelin glycoprotein), bind to the Nogo-66 receptor (NgR) and inhibit axonal growth in vitro. Transgenic or viral blockade of NgR function allows axonal sprouting in vivo. Here, we administered the soluble function-blocking NgR ectodomain [aa 27-310; NgR(310)ecto] to spinal-injured rats. Purified NgR(310)ecto-Fc protein was delivered intrathecally after midthoracic dorsal over-hemisection. Axonal sprouting of corticospinal and raphespinal fibers in NgR(310)ecto-Fc-treated animals correlates with improved spinal cord electrical conduction and improved locomotion. The ability of soluble NgR(310)ecto to promote axon growth and locomotor recovery demonstrates a therapeutic potential for NgR antagonism in traumatic spinal cord injury.

A neutralizing anti-Nogo66 receptor monoclonal antibody reverses inhibition of neurite outgrowth by central nervous system myelin.

The Nogo66 receptor (NgR1) is a neuronal, leucine-rich repeat (LRR) protein that binds three central nervous system (CNS) myelin proteins, Nogo, myelin-associated glycoprotein, and oligodendrocyte myelin glycoprotein, and mediates their inhibitory effects on neurite growth. Although the LRR domains on NgR1 are necessary for binding to the myelin proteins, the exact epitope(s) involved in ligand binding is unclear. Here we report the generation and detailed characterization of an anti-NgR1 monoclonal antibody, 7E11. The 7E11 monoclonal antibody blocks Nogo, myelin-associated glycoprotein, and oligodendrocyte myelin glycoprotein binding to NgR1 with IC50 values of 120, 14, and 4.5 nm, respectively, and effectively promotes neurite outgrowth of P3 rat dorsal root ganglia neurons cultured on a CNS myelin substrate. Further, we have defined the molecular epitope of 7E11 to be DNAQLR located in the third LRR domain of rat NgR1. Our data demonstrate that anti-NgR1 antibodies recognizing this epitope, such as 7E11, can neutralize CNS myelin-dependent inhibition of neurite outgrowth. Thus, specific anti-NgR1 antibodies may represent a useful therapeutic approach for promoting CNS repair after injury.

Mutations of the anti-mullerian hormone gene in patients with persistent mullerian duct syndrome: biosynthesis, secretion, and processing of the abnormal proteins and analysis using a three-dimensional model.

Anti-Müllerian hormone (AMH), a TGF-beta family member, determines whether an individual develops a uterus and Fallopian tubes. Mutations in the AMH gene lead to persistent Müllerian duct syndrome in males. The wild-type human AMH protein is synthesized as a disulfide-linked dimer of two identical 70-kDa polypeptides, which undergoes proteolytic processing to generate a 110-kDa N-terminal dimer and a bioactive 25-kDa TGF-beta-like C-terminal dimer. We have studied the biosynthesis and secretion of wild-type AMH and of seven persistent Müllerian duct syndrome proteins, containing mutations in either the N- or C-terminal domain. Mutant proteins lacking the C-terminal domain are secreted more rapidly than full-length AMH, whereas single amino acid changes in both domains can have profound effects on protein stability and folding. The addition of a cysteine in an N-terminal domain mutant, R194C, prevents proper folding, whereas the elimination of the cysteine involved in forming the interchain disulfide bond, in a C-terminal domain mutant, C525Y, leads to a truncation at the C terminus. A molecular model of the AMH C-terminal domain provides insights into how some mutations could affect biosynthesis and function.