Form Of Nerve Growth Factor Research Articles

The p75 neurotrophin receptor inhibitor, LM11A-31, ameliorates acute stroke injury and modulates astrocytic proNGF

The precursor form of nerve growth factor (proNGF) is essential to maintain NGF survival signaling. ProNGF is also among endogenous ligands for p75 neurotrophin receptor (p75ntr). Mounting evidence implies that p75ntr signaling contributes to neural damage in ischemic stroke. The present study examines the therapeutic effect of the p75ntr modulator LM11A-31. Adult mice underwent transient distal middle cerebral artery occlusion (t-dMCAO) followed by LM11A-31 treatment (25 mg/kg, i.p., twice daily) either for 72 h post-injury (acute phase) or afterward till two weeks post-stroke (subacute phase). LM11A-31 reduced blood-brain barrier permeability, cerebral tissue injury, and sensorimotor function in the acute phase of stroke. Ischemic brain samples showed repressed proNGF/P75ntr signaling and Caspase 3 activation in LM11A-31 treated mice, where we observed less reactive microglia and IL-1β production. LM11A-31 (20–80 nM) also mitigated neural injury induced by oxygen-glucose deprivation (OGD) in sandwich co-cultures of primary cortical neurons (PCN) and astrocytes. This concurred with JNK/PARP downregulation and reduced caspase-3 cleavage in the PCNs and was associated with repressed proNGF generation in astrocytes. Further in vitro experiments indicated human proNGF suppresses the pro-inflammatory phenotype in microglial cultures, as determined by a sharp decline in HMGB-1 production and moderate arginase-1 upregulation. Despite significant protection in acute stroke, LM11A-31 treatment did not improve cortical atrophy and sensorimotor function in the subacute phase. Our findings provide preclinical evidence supporting LM11A-31 as a promising therapy for acute stroke injury. Further investigations may elucidate if reduced astrocytic proNGF, an endogenous reservoir of pro-neurotrophins, may restrict the therapeutic window.

MP31-12 OVERACTIVE BLADDER SYNDROME IS ASSOCIATED WITH ELEVATED URINARY PRONGF TO NGF RATIO IN AN AGING FEMALE POPULATION

INTRODUCTION AND OBJECTIVE: The clinical relevance of the ratio NGF/creatinine in urine as a biomarker for overactive bladder syndrome (OAB) diagnosis is a matter of debate. ProNGF, the precursor form of nerve growth factor (NGF) was recently found to possess degenerative roles by signalling through its receptor p75NTR. The present study aims to identify the changes in concentration of NGF and proNGF, and the soluble factors involved in their proteolysis in the urine of an aging female population with OAB. METHODS: Urine samples were obtained from 20 females of 50-80 years of age with OAB and from 20 controls of the same age group. Analyses were carried out with highly specific ELISA and enzymatic kits. Participants completed a full clinical evaluation and validated self-reported questionnaires of lower urinary tract symptoms as well as a one-day voiding diary. RESULTS: NGF ELISA kit specificity was confirmed. ProNGF/NGF ratio was significantly increased in the urine of OAB subjects. Enzymatic activities of plasmin and matrix metalloproteinase 7 (MMP-7), the main enzymes responsible for extracellular processing of proNGF to NGF, were similar between controls and OAB when normalized to their respective inhibitors, α2-antiplasmin inhibitor and TIMP-1. On the other hand, metalloproteinase 9 (MMP-9), the enzyme responsible for the proteolysis of NGF into peptides, displayed a marked increased activity even when normalized to its inhibitor TIMP-1. On the other hand, nitric oxide and PGE2, two factors increasing expression and activity of MMP-9, also displayed higher concentrations in urine of OAB patients. CONCLUSIONS: The ratio ProNGF/NGF could constitute a more reliable biomarker for OAB rather than NGF level alone. This increase could originate from MMP-9 overactivity enhancing NGF proteolysis in OAB. This suggests that MMP9 inhibitors could constitute a new therapeutic target to treat OAB patients. Source of Funding: Urology Care Foundation Rising Star in Urology Research Award and the Quebec Network for Research on Aging

Development of a Cell-Based Assay to Assess Binding of the proNGF Prodomain to Sortilin

Sortilin was first identified based on its activity as part of intracellular protein sorting machinery. Recently, it was discovered that sortilin also acts as a cell surface receptor for the propeptide form of nerve growth factor (proNGF), progranulin, and neurotensin. The interaction of sortilin to these neurotrophic ligands is linked to diseases of the nervous system that lead to neurodegeneration and neuropathic pain. Blocking of the interaction of sortilin to these ligands may prevent or slow the progress of these nervous system disorders. In vitro screening assays for blocking compounds or peptides are part of the standard set of tools for drug discovery. However, assays for sortilin biology are not readily available to determine if the selected blocking agent inhibits sortilin activity on the surface of cells. We have developed a sortilin specific cell based assay to identify compounds that specifically block interaction between sortilin and proNGF prodomain. The assay system records both the presence of sortilin on the cell surface and the interaction with the pro domain of NGF. Fluorescent images of the sortilin expressing cells are analyzed for the presence of pro domain of NGF. Sortilin-positive and sortilin-negative cells within one well are concomitantly and automatically analyzed. Sortilin—pro domain interaction can be blocked dose dependently by neurotensin and synthetic compounds. The assay will facilitate the discovery of entities interfering with the binding of sortilin to the NGF pro domain. This assay can be modified to screen for inhibitors of the binding of ligands to other complex cell surface receptors.

Opposing Effects of NGF and proNGF on HIV Induced Macrophage Activation.

Macrophage and microglial activation by HIV in the central nervous system (CNS) triggers the secretion of soluble factors which damage neurons. Therapeutic approaches designed to restore cognitive function by suppressing this inflammatory activity have not yet been successful. Recent studies have indicated that the phenotype of macrophages is differentially controlled by the mature and pro form of nerve growth factor. These cells therefore may be highly responsive to the imbalance in pro versus mature neurotrophins often associated with neurodegenerative diseases. In this study we evaluated the interactions between neurotrophins and HIV induced macrophage activation. HIV stimulation of macrophages induced a neurotoxic phenotype characterized by the expression of podosomes, suppression of calcium spiking and increased neurotoxin production. The secretome of the activated macrophages revealed a bias toward anti-angiogenic like activity and increased secretion of MMP-9. Co-stimulation with NGF and HIV suppressed neurotoxin secretion, increased calcium spiking, suppressed podosome expression and reversed 86% of the proteins secreted in response to HIV, including MMP-9 and many growth factors. In contrast, co-stimulation of macrophages with proNGF not only failed to reverse the effects of HIV but increased the neurotoxic phenotype. These differential effects of proNGF and NGF on HIV activation provide a potential novel therapeutic avenue for controlling macrophage activation in response to HIV.

Combined therapy with methylprednisolone and ulinastatin in experimental autoimmune encephalomyelitis

Background Our previous study had demonstrated that ulinastatin (UTI) had a neuroprotective effect in experimental autoimmune encephalomyelitis (EAE). Methylprednisolone has been recommended to be a standard drug in multiple sclerosis (MS) therapies. The present study was to investigate the protective effects of UTI combined methylprednisolone in EAE. Methods Mice were divided into a UTI treatment group, a methylprednisolone treatment group, a combined treatment group with UTI and methylprednisolone, a normal saline treatment group, and a normal control group. EAE mice were induced in groups receiving different combined treatments, or respective monotherapies. Demyelination was evaluated by Solochrome cyanin staining. 2′,3′-cyclic nucleotide 3′- phosphodiesterase (CNP)/ myelin basic protein (MBP)/ the precursor form of nerve growth factor (proNGF)/p75/ inducible nitric oxide synthase (iNOS) proteins in cerebral cortex of EAE were detected by Western blotting. Results The combined treatment group had a lower clinical score ( 0.61±0.06) and demyelinating score (1.33±0.33) than the groups with normal saline (clinical score: 1.39±0.08, P <0.001; demyelinating score: 2.75±0.49, P <0.05) or monotheraphies. Compared with the saline treated EAE group, UTI combined methylprednisolone significantly increased expressions of CNP (1.14±0.06 vs. 0.65±0.04, P <0.001), MBP (1.28±0.14 vs. 0.44±0.17, P <0.001), and decreased expressions of proNGF (1.08±0.10 vs. 2.32±0.12, P <0.001), p75 (1.13±0.13 vs. 2.33±0.17, P <0.001), and iNOS (1.05±0.31 vs. 2.17±0.13, P <0.001) proteins in EAE. Furthermore, UTI combined methylprednisolone could significantly upregulate MBP (1.28±0.14 vs. 1.01±0.15, P <0.05) expression and downregulate iNOS (1.05±0.31 vs. 1.35±0.14, P <0.05) expression compared to methylprednisolone treatment EAE group. And proNGF expression was significantly lower in combined treatment (1.08±0.10) than that in UTI (1.51±0.24, P <0.05) or methylprednisolone (1.31±0.04, P <0.05) treatment group. Conclusion Combination treatment of UTI with methylprednisolone was shown to protect EAE, suggesting that combination therapy is a potential novel treatment in MS.

Possible Influence of a Non-Synonymous Polymorphism Located in the NGF Precursor on Susceptibility to Late-Onset Alzheimer's Disease and Mild Cognitive Impairment

The complex network of neurotrophic factors is supposed to play a role in neurodegeneration, but the effect of variations in their coding genes on susceptibility to sporadic Alzheimer's disease is not established. The mature form of nerve growth factor (NGF) derives from a precursor, proNGF, which was recently discovered to exert crucial functions in brain. We designed a case-control association study to test the hypothesis as to whether polymorphisms located in the proNGF genomic region influence the liability to Alzheimer's disease and its prodromal form, mild cognitive impairment. Three independent case-control samples, with individuals aged >60 years, were collected in Italian Alzheimer Units. One polymorphism located in the proNGF region, rs6330, demonstrated a minor allele frequency >5% and was used in the association study. The minor allele of rs6330 was more frequent in patients from the three sample series as compared to respective normal controls. Multivariate logistic regression showed a significant association under the dominant model in one cohort (OR 1.83, 95% CI 1.00-3.54) and in the pooled case-control sample (OR 1.47, 95% CI 1.03-2.08). These findings further suggest that proNGF may play a role in Alzheimer-type neurodegeneration and that genetic variations in the NGF locus may influence the occurrence of sporadic, late-onset Alzheimer's disease.

Neurotrophic Factor Changes in the Rat Thick Skin following Chronic Constriction Injury of the Sciatic Nerve

BackgroundCutaneous peripheral neuropathies have been associated with changes of the sensory fiber innervation in the dermis and epidermis. These changes are mediated in part by the increase in local expression of trophic factors. Increase in target tissue nerve growth factor has been implicated in the promotion of peptidergic afferent and sympathetic efferent sprouting following nerve injury. The primary source of nerve growth factor is cells found in the target tissue, namely the skin. Recent evidence regarding the release and extracellular maturation of nerve growth factor indicate that it is produced in its precursor form and matured in the extracellular space. It is our hypothesis that the precursor form of nerve growth factor should be detectable in those cell types producing it. To date, limitations in available immunohistochemical tools have restricted efforts in obtaining an accurate distribution of nerve growth factor in the skin of naïve animals and those with neuropathic pain lesions. It is the objective of this study to delineate the distribution of the precursor form of nerve growth factor to those cell types expressing it, as well as to describe its distribution with respect to those nerve fibers responsive to it.ResultsWe observed a decrease in peptidergic fiber innervation at 1 week after the application of a chronic constriction injury (CCI) to the sciatic nerve, followed by a recovery, correlating with TrkA protein levels. ProNGF expression in CCI animals was significantly higher than in sham-operated controls from 1-4 weeks post-CCI. ProNGF immunoreactivity was increased in mast cells at 1 week post-CCI and, at later time points, in keratinocytes. P75 expression within the dermis and epidermis was significantly higher in CCI-operated animals than in controls and these changes were localized to neuronal and non-neuronal cell populations using specific markers for each.ConclusionsWe describe proNGF expression by non-neuronal cells over time after nerve injury as well as the association of NGF-responsive fibers to proNGF-expressing target tissues. ProNGF expression increases following nerve injury in those cell types previously suggested to express it.

Cell Death and Learning Impairment in Mice Caused by in Vitro Modified Pro-NGF Can Be Related to Its Increased Oxidative Modifications in Alzheimer Disease

Pro-nerve growth factor (pro-NGF) is expressed at increased levels in Alzheimer's disease (AD)-affected brains and is able to induce cell death in cultures; however, the reasons for these phenomena remain elusive. Here we show that pro-NGF in human AD-affected hippocampus and entorhinal cortex is modified by advanced glycation and lipoxidation end-products in a stage-dependent manner. These modifications block pro-NGF processing to mature NGF, thus making the proneurotrophin especially effective in inducing apoptosis of PC12 cells in culture through the p75 neurotrophin receptor. The processing of advanced glycation and lipoxidation end-products in vitro modified recombinant human pro-NGF is severely impaired, as evidenced by Western blot and by examining its physiological functionality in cell cultures. We also report that modified recombinant human pro-NGF, as well as pro-NGF isolated from human brain affected by AD, cause impairment of learning tasks when administered intracerebroventricularly in mice, which correlates with AD-associated learning impairment. Taken together, the data we present here offer a novel pathway of ethiopathogenesis in AD caused by advanced glycation and lipoxidation end-products modification of pro-NGF.

Amyloid β-Induced Nerve Growth Factor Dysmetabolism in Alzheimer Disease

We previously reported that the precursor form of nerve growth factor (pro-NGF) and not mature NGF is liberated in the CNS in an activity-dependent manner, and that its maturation and degradation occur in the extracellular space by the coordinated action of proteases.Here, we present evidence of diminished conversion of pro-NGF to its mature form and of greater NGF degradation in Alzheimer disease (AD) brain samples compared with controls. These alterations of the NGF metabolic pathway likely resulted in the increased pro-NGF levels. The pro-NGF was largely in a peroxynitrited form in the AD samples. Intrahippocampal injection of amyloid-beta oligomers provoked similar upregulation of pro-NGF in naive rats that was accompanied by evidence of microglial activation (CD40), increased levels of inducible nitric oxide synthase, and increased activity of the NGF-degrading enzyme matrix metalloproteinase 9. The elevated inducible nitric oxide synthase provoked the generation of biologically inactive, peroxynitrite-modified pro-NGF in amyloid-beta oligomer-injected rats. These parameters were corrected by minocycline treatment. Minocycline also diminished altered matrix metalloproteinase 9, inducible nitric oxide synthase, and microglial activation (CD40); improved cognitive behavior; and normalized pro-NGF levels in a transgenic mouse AD model. The effects of amyloid-beta amyloid CNS burden on NGF metabolism may explain the paradoxical upregulation of pro-NGF in AD accompanied by atrophy of forebrain cholinergic neurons.

The Diversity of Bioactive Proteins in Australian Snake Venoms

Australian elapid snakes are among the most venomous in the world. Their venoms contain multiple components that target blood hemostasis, neuromuscular signaling, and the cardiovascular system. We describe here a comprehensive approach to separation and identification of the venom proteins from 18 of these snake species, representing nine genera. The venom protein components were separated by two-dimensional PAGE and identified using mass spectrometry and de novo peptide sequencing. The venoms are complex mixtures showing up to 200 protein spots varying in size from <7 to over 150 kDa and in pI from 3 to >10. These include many proteins identified previously in Australian snake venoms, homologs identified in other snake species, and some novel proteins. In many cases multiple trains of spots were typically observed in the higher molecular mass range (>20 kDa) (indicative of post-translational modification). Venom proteins and their post-translational modifications were characterized using specific antibodies, phosphoprotein- and glycoprotein-specific stains, enzymatic digestion, lectin binding, and antivenom reactivity. In the lower molecular weight range, several proteins were identified, but the predominant species were phospholipase A2 and alpha-neurotoxins, both represented by different sequence variants. The higher molecular weight range contained proteases, nucleotidases, oxidases, and homologs of mammalian coagulation factors. This information together with the identification of several novel proteins (metalloproteinases, vespryns, phospholipase A2 inhibitors, protein-disulfide isomerase, 5'-nucleotidases, cysteine-rich secreted proteins, C-type lectins, and acetylcholinesterases) aids in understanding the lethal mechanisms of elapid snake venoms and represents a valuable resource for future development of novel human therapeutics.

Post-translational modification accounts for the presence of varied forms of nerve growth factor in Australian elapid snake venoms

The Australian elapid snakes are amongst the most venomous snakes in the world, but much less is known about the overall venom composition in comparison to Asian and American snakes. We have used a combined approach of cDNA cloning and 2-DE with MS to identify nerve growth factor (NGF) in venoms of the Australian elapid snakes and demonstrate its neurite outgrowth activity. While a single 730 nucleotide ORF, coding for a 243 amino acid precursor protein was detected in all snakes, use of 2-DE identified NGF proteins with considerable variation in molecular size within and between the different snakes. The variation in size can be explained at least in part by N-linked glycosylation. It is possible that these modifications alter the stability, activity and other characteristics of the snake NGFs. Further characterisation is necessary to delineate the function of the individual NGF isoforms.

Pro-NGF from Alzheimer's Disease and Normal Human Brain Displays Distinctive Abilities to Induce Processing and Nuclear Translocation of Intracellular Domain of p75NTR and Apoptosis

The pro form of neurotrophic growth factor (pro-NGF), purified by chromatography from human Alzheimer's disease (AD)-affected brains (ADhbi-pro-NGF), has been shown to induce apoptotic cell death in neuronal cell cultures through its interaction with the p75 neurotrophin receptor (p75NTR). In the present work, we report that ADhbi-pro-NGF stimulates processing of p75NTR with alpha- and gamma-secretases, yielding a 20-kd intracellular domain (p75(ICD)) that translocates to the nucleus. This process was accompanied by delayed apoptosis. In AD, p75(ICD) was significantly increased in human entorhinal cortex. Although human frontal cortex has been described as showing a higher pro-NGF increase in AD, the increase in the entorhinal cortex paralleled p75NTR processing in its intracellular domain. In addition, pro-NGF isolated from AD-affected brains differed functionally from pro-NGF isolated from comparably aged control brains, with pro-NGF isolated from control brains being unstable and undergoing degradation to NGF when added to cell culture. As p75(ICD) and pro-NGF are both mediators of apoptosis and are both found in increased levels in the cerebral cortex in AD, the present data have implications for understanding neuronal degeneration in AD.

Pro-NGF Isolated from the Human Brain Affected by Alzheimer's Disease Induces Neuronal Apoptosis Mediated by p75NTR

The pro-form of nerve growth factor (pro-NGF) has been shown to be a high affinity ligand for p75NTR and to induce apoptosis through this receptor. It has been reported that pro-NGF, rather than mature NGF, is the predominant form of this neurotrophin in human brain. In the present work we studied the potential involvement of pro-NGF purified from human brains affected by Alzheimer's disease (AD), where it is especially abundant, in the neuronal apoptosis observed in this disease. Western blot analysis of human brain tissue showed the existence of several pro-NGF forms. Some of these pro-NGF forms were significantly increased in AD brain cortex in a disease stage-dependent manner. Pro-NGF, purified by chromatography from human AD brains, induced apoptotic cell death in sympathetic neurons and in a p75NTR stably transfected cell line. Blocking p75NTR in cell culture abolished neuronal apoptosis caused by pro-NGF. p75NTR-transfected cells underwent apoptosis in the presence of pro-NGF while control wild-type cells did not. Taken together, these results indicate that pro-NGF purified from AD human brains can induce apoptosis in neuronal cell cultures through its interaction with the p75NTR receptor.

The Precursor Pro-Nerve Growth Factor Is the Predominant Form of Nerve Growth Factor in Brain and Is Increased in Alzheimer's Disease

Nerve growth factor (NGF) is important for regulation, differentiation, and survival of peripheral and central nervous system neurons, including basal forebrain cholinergic neurons (BFCN) which degenerate in Alzheimer's disease (AD). Mature NGF protein is processed from a larger precursor, proNGF. We demonstrate that proNGF is the predominant form of NGF in mouse, rat, and human brain tissue, whereas little or no mature NGF is detected. Previous reports showed NGF protein, measured by ELISA, is increased in AD BFCN target regions such as hippocampus and cortex. Using Western blotting, we demonstrate a twofold increase in proNGF in AD parietal cortex compared to controls, indicating that it is this precursor form, proNGF, that accumulates in AD. This increase may reflect either a role for biologically active proNGF or posttranslational disturbances in NGF biosynthesis that decrease the processing of proNGF to mature NGF in AD.

7S nerve growth factor has different biological activity from 2.5S nerve growth factor in vitro

It is considered that two molecular forms of nerve growth factor (NGF), that is 7S NGF and 2.5S NGF have the identical neurotrophic effect on neurons. We now report that 7S NGF has different biological activities from 2.5S NGF in vitro. 7S NGF could promote the survival and neurite outgrowth of neurons from newborn rat hippocampus, cortex and cerebellum and stimulate the proliferation of astrocytes in vitro, but 2.5S NGF had no such effect.

Crystallization and characterization of the high molecular weight form of nerve growth factor (7 S NGF)

A high molecular weight form of nerve growth factor (7 S NGF) has been crystallized in two crystal forms from polyethylene glycol 4000 by the vapour diffusion technique. The orthorhombic form A belongs to the space group P2 1 2 1 2 1 and has cell dimensions of a = 95.6, b = 96.5 and c = 147.0 A ̊ . With synchrotron X-ray radiation, these crystals diffract to 2.8 Å resolution. They contain an intact 7 S NGF complex in the asymmetric unit. The tetragonal form B, which grows at similar conditions to the A form, belongs to the space group P4 1 2 1 2 (or P4 3 2 1 2) with unit cell dimensions of a = 97.4, b = 97.4 and c = 308.3 A ̊ . These crystals diffract to 3.6 Å resolution and contain one 7 S complex per asymmetric unit-Native X-ray data have been collected to 3.3 Å for the A form and to 5.0 Å for the B form, both using synchrotron radiation.

Subunit structure of high molecular weight mouse nerve growth factor.

Studies from several laboratories have shown that mouse submandibular glands and mouse saliva contain nerve growth factor (NGF) as part of a high molecular weight oligomeric macromolecule composed of three different subunits, termed alpha, beta, and gamma. The beta-subunit is the nerve growth-promoting protein. The gamma-subunit is a serine protease class enzyme of highly restricted substrate specificity. The alpha-subunit has no known function. This high molecular weight form of nerve growth factor is also a Zn(II)-containing metalloprotein. In the present study, measurements of multiple physicochemical parameters have been used to deduce the subunit structure of high molecular weight NGF. Results demonstrate that it contains two alpha-, one beta- and one gamma-subunit together with one tightly bound Zn(II) ion per molecule.

Molecular forms of nerve growth factor in mouse submaxillary glands

By use of immunoblot analysis, we demonstrate the presence of a nerve growth factor with a relative molecular mass (Mr) of 53,000 in submaxillary glands of adult male and female mice in addition to the 13,000 form previously discovered in this tissue. Both the Mr 53,000 and 13,000 forms of nerve growth factor are present at equal concentrations in salivary glands of male mice while the Mr 53,000 form is present at a greater concentration than the Mr 13,000 form in the glands of female mice. Testosterone pretreatment, however, specifically augments the Mr 13,000 form of nerve growth factor in the salivary glands of female mice. The existence of nerve growth factor with molecular weight of 53,000, which is higher than the molecular size predicted for the two precursor forms of nerve growth factor, suggest the possibility that one of the nerve growth factor precursors or a product derived from it may undergo post-translational modification in submaxillary glands of mice.

Detection of molecules with nerve growth factor binding activity in medium conditioned by L-929 fibroblasts

L-929 fibroblasts (L cells) secrete a high molecular weight form of nerve growth factor (NGF) that is non-covalently bound and contains as part of its structure a molecule similar, if not identical, to β-NGF in mouse submandibular glands. The other components of the NGF complex have not been characterized. In this study we used radiolabeled β-NGF as a probe to detect molecules with NGF binding activity in L cell conditioned medium. The L cell NGF complex was dissociated at low pH, or with denaturants or detergents, and allowed to reassociate in the presence of 125I-β-NGF. Radioactivity became associated with a complex that eluted in a high molecular weight volume on columns of Sephadex G-200 and Sephacryl S-500. Incorporation was saturable and did not occur under non-dissociating conditions. The complex was affinity cross-linked and studied by SDS gel electrophoresis. Radiolabeled molecules were observed with molecular weights of 151,000, 56,000 and 53,000. Labeling did not occur in the presence of excess unlabeled NGF or when cross-linking was done with fetal bovine serum, indicating that binding is specific and that binding activity is not derived from serum added to tissue culture medium. Solutions containing 7S NGF from mouse salivary glands were cross-linked by similar procedures but different banding patterns were observed. The data show that NGF binding molecules dissimilar from those in salivary glands are present in L cell conditioned medium.

Synthesis and secretion of a high molecular weight form of nerve growth factor by skeletal muscle cells in culture.

Rat skeletal muscle cells and a cloned myogenic cell line synthesize and secrete in culture a molecule that is immunologically and biologically indistinguishable from the active form of nerve growth factor (NGF) from mouse submandibular gland. This protein can be detected in medium conditioned by muscle cells both before and after fusion and in the soluble fraction of muscle cell homogenates. Chromatographic data also reveal that the molecular properties of muscle cell NGF differ from those of the growth factor purified from mouse submandibular glands. Muscle cell NGF has a molecular weight between 140,000 and 160,000, whereas purified mouse gland NGF has a molecular weight of 26,000. The biologic function of muscle cell NGF is not known, although it could be that it plays some role relating to the association of nerves and muscle in vivo.