Antiserum against rat peripheral nervous system (PNS) myelin contained immunoglobulins which bound preferentially to the extracellular surfaces of myelin-related Schwann cells in intact cultures of dorsal root ganglion (DRG) neurons and Schwann cells, while antiserum against basic protein (BP) from central nervous system myelin or the PNS basic protein P2 did not. We demonstrate the presence of PNS myelin proteins P1 (identical to BP) and P2 by immunoperoxidase techniques in DRG cultures that had been treated to disrupt cellular membranes. These observations suggest that P1 and P2 are not exposed on the extracellular surfaces of myelin-related Schwann cells in culture. The results also supported the hypothesis concerning the possible mechanisms by which anti-PNS myelin serum demyelinates DRG cultures, while anti-BP serum and anti-P2 serum do not.

Experimental allergic neuritis (EAN) was induced in rhesus monkey (Macaca mulatta) following sensitization with rabbit nerve (PNS) myelin in complete Freund's adjuvant (CFA) or with bovine P2 protein complexed with phosphatidyl serine (P2-lipid) in CFA. The response of monkeys receiving PNS myelin in CFA differed from the previous studies where monkeys developed clinical signs of fatal EAN within 15-20 days following sensitization. The monkeys in this study (6) showed a much longer delay (40-114 days) before the appearance of severe clinical signs, and 4 of the 6 animals survived without further attack (1 year). Monkeys (4) injected with P2-lipid (2:1 ratio; w/w) developed severe clinical signs of EAN which was fetal in 3 cases. Peripheral lymphocytes from monkeys sensitized to the P2-lipid showed a much stronger mitogeneic response to P2 protein than those from the PNS myelin-sensitized monkeys. on quantitation of the circulating anti-P2 antibodies, the P2-sensitized monkeys generally had much titers than those sensitized with PNS myelin.

P2 protein is a small basic protein (Mr = 14,820) found in peripheral nerve myelin and spinal cord myelin. There is now overwhelming evidence that P2 protein is the crucial antigen involved in the induction of experimental allergic neuritis, an autoimmune disease of the peripheral nervous system. The complete amino acid sequence of rabbit P2 protein was derived by sequence analysis of cyanogen bromide peptides and peptides obtained by proteolysis using Staphylococcus aureus V8 enzyme, trypsin, or clostripain. There are 131 amino acids and an excess of the basic amino acids lysine and arginine; histidine is absent. There are 3 highly hydrophobic regions in the P2 molecule. Probability analysis of the sequence predicts a high degree of beta structure, essentially in agreement with CD data.

We studied the effects of antiserum against rat peripheral nervous system (PNS) myelin, rat or chicken central nervous system myelin basic protein (BP), or rabbit P2 protein from PNS myelin on myelinated cultures containing only rat dorsal root ganglion neurons and Schwann cells. While anti-PNS myelin serum consistently produced segmental PNS demyelination, anti-BP serum and anti-P2 serum did not. The culture results suggest that the myelin PNS proteins P1 (identical to basic protein from central nervous system myelin) and P2 are not exposed on the extracellular surfaces of myelin-related Schwann cells in tissue culture.

Antibody binding to human CNS myelin basic protein and to rabbit sciatic nerve myelin P-2 in their lipid-bound and water-soluble conformations has been investigated. 125I-labeled basic protein or P-2 was bound to the surface of liposomes (vesicles) of different acidic lipids, phosphatidylethanolamine (PE), phosphatidylserine (PS), phosphatidic acid (PA), phosphatidylglycerol (PG), and cerebroside sulfate (CBS). The antibody was prepared against aqueous solutions of basic protein and P-2. Antibody binding to the proteins in liposomes was measured by precipitation of the liposomes by using a double antibody radioimmunoassay. The amount of 125I-basic protein precipitated was lest when the protein was bound to PA and increased in the order PA less than PS less than PG less than CBS less than PE approximately equal to basic protein in solution, suggesting that the antigenic determinants were lest exposed or most altered for PA and most exposed for PE. This agreed fairly well with previously published biophysical studies that suggested that hydrophobic segments of the protein penetrated into the lipid bilayer and that this penetration decreased in the order PA approximately equal to PG greater than PS greater than CBS greater than or equal to PE. The amount of 125I-P-2 precipitated was least for PA and CBS and increased in the order PA approximately equal to CBS less than PS less than PG less than PE approximately equal to P-2 in solution. However, the differences were less than for basic protein and the effect of CBS was different for the 2 proteins. Less is known about the conformation of P-2 in these lipids but it is known that lipids increase its disease-inducing activity. These results indicate that interaction with lipid may sequester or alter the conformation of antigenic determinants such that antibody binding decreases.

Peptide CN1, a large 93 residue peptide, derived from residues 21-113 of the bovine and rabbit P2 protein of sciatic nerve myelin, induces severe allergic neuritis in Lewis rats. When complexed with phosphatidylserine and tested at 50 microgram dosage in Freund's complete adjuvant, it induces severe clinical and histologic signs (cellular infiltration and demyelination of the sciatic nerve) in most animals. It is as potent in disease induction as the P2 protein on a weight basis. In contrast, when not complexed with phosphatidylserine, Peptide CN1 induced only mild clinical signs and histologic lesions in 3 of 10 rats. CNBr peptides CN2 and CN3, derived from the carboxyl and amino terminal ends, respectively, were not active. Spleen and lymph node cells from rats sensitized to Peptide CN1 responded to both P2 and Peptide CN1 in culture in the mitogenic assay. These data show that the major neuritogenic domain for the rat resides in the CN1 region.

The P2 protein, a small, highly ordered basic protein of peripheral nerve myelin, is a potent inducer of allergic neuritis in rats when complexed with phospholipids such as phosphatidylserine. lsolated P2 protein administered without lipid is a poor neuritogen, and if first oxidized with performic acid, aminoethylated in 8 M urea or heat denatured, it loses nearly all activity. When the aminoethylated or oxidized forms are combined with phosphatidylserine, however, they recover essentially full neuritogenic activity. Complexing with lipid also greatly enhances the activity of the heat denatured form. Spleen cells sensitized to the aminoethylated and heated forms of P2 protein show a pronounced mitogenic response to either of these forms as well as to the P2 protein itself, but only when sensitization is initiated with the lipid complex. These data indicate that the lipid complex reverses the distortion acquired by chemical treatment or denaturation and converts the P2 molecule into a conformation approximating that of the native P2 protein in myelin. These studies imply that the neuritogenic domain, while highly sensitive to denaturing conditions, requires interaction with phospholipids in order to attain the most favourable conformation for inducing a cell-mediated response that leads to disease.

Journal of NeurochemistryVolume 31, Issue 1 p. 375-379 Glycoproteins and albumin in peripheral nerve myelin M. W. Roomi, M. W. Roomi Playfair Neuroscience Unit, University of Toronto, 1 Spadina Crescent, Toronto, Canada.Search for more papers by this authorA. Ishaque, A. Ishaque Playfair Neuroscience Unit, University of Toronto, 1 Spadina Crescent, Toronto, Canada.Search for more papers by this authorN. R. Khan, N. R. Khan Playfair Neuroscience Unit, University of Toronto, 1 Spadina Crescent, Toronto, Canada.Search for more papers by this authorE. H. Eylar, Corresponding Author E. H. Eylar Playfair Neuroscience Unit, University of Toronto, 1 Spadina Crescent, Toronto, Canada.To whom reprint requests should be sent.Search for more papers by this author M. W. Roomi, M. W. Roomi Playfair Neuroscience Unit, University of Toronto, 1 Spadina Crescent, Toronto, Canada.Search for more papers by this authorA. Ishaque, A. Ishaque Playfair Neuroscience Unit, University of Toronto, 1 Spadina Crescent, Toronto, Canada.Search for more papers by this authorN. R. Khan, N. R. Khan Playfair Neuroscience Unit, University of Toronto, 1 Spadina Crescent, Toronto, Canada.Search for more papers by this authorE. H. Eylar, Corresponding Author E. H. Eylar Playfair Neuroscience Unit, University of Toronto, 1 Spadina Crescent, Toronto, Canada.To whom reprint requests should be sent.Search for more papers by this author First published: July 1978 https://doi.org/10.1111/j.1471-4159.1978.tb12476.xCitations: 17Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume31, Issue1July 1978Pages 375-379 RelatedInformation

A glycoprotein, referred to as PO protein, was isolated from rabbit sciatic nerve myelin by gel filtration on Agarose 0.5 m in dodecyl sulfate. The purified myelin was first defatted and extracted at pH 2. The water-soluble proteins such as myelin basic protein and P2 protein were extracted leaving a glycoprotein-rich residue, from which the PO protein was isolated. The purified protein showed a single band on gel electrophoresis in dodecyl sulfate when stained with Coomassie Blue of periodic acid-Schiff reagent. The carbohydrate, comprising 6.3% by weight, appears to exist as a nonasaccharide unit having 3 mannose, 3 N-acetylglucosamine, 1 sialic acid, 1 galactose and 1 fucose residue. The polypeptide moiety has a high content of non-polar amino acids. A single amino acid, isoleucine, was found at the NH2-terminal end by dansyl and Edman procedures. The PO protein is the major protein of peripheral nerve myelin.

When purified rabbit sciatic nerve myelin, whether lyophilized or not, is treated with low amounts of trypsin (25 μg/ml) for 0.5, 3, or 24 h the resulting protein patterns viewed on sodium dodecyl sulfate (SDS) gel electrophoresis are similar. The most striking feature of the trypsinized myelin is the accumulation of a heavy band at the basic protein position, molecular weight 19 000, which is accounted for as a degradation product of the PO protein, referred to as the TPO protein. The PO protein, the major glycoprotein of sciatic nerve myelin, as well as the 23K and P2 proteins and albumin, an absorbed component, are all partially degraded; most high molecular weight bands are lost. The TPO protein, isolated by gel filtration in 2% SDS on an agarose column, like the PO protein, is highly insoluble in aqueous solvents. It is a glycoprotein (8% carbohydrate), staining with periodic acid-Schiff reagent; containing 3 mannose, 1 galactose, 3 N-acetylglucosamine, 1 sialic acid, and 1 fucose residues and is identical to the nonasaccharide of the parent PO protein. The amino acid composition of the TPO protein, is similar to the PO protein, but has a much higher content of hydrophobic residues and begins with NH2-methionine. This suggests that the PO protein is an amphipathic membrane protein in which its more polar character is confined to the first third of its NH2-terminus. This polar domain is probably positioned above the lipid leaflet where it is accessible to trypsin which cleaves a sensitive lysinyl (or argininyl)-methionine linkage. The more hydrophobic domain (the TPO protein) is buried in the myelin bilayer where it is protected from further tryptic attack. Thus trypsin can serve as a useful probe of myelin structure.

Although cell-mediated hypersensitivity to basic myelin protein has been demonstrated in multiple sclerosis with use of cell migration assays, results with the lymphoblastic transformation technique have been inconclusive. However, prospective studies relating results of lymphoblastic transformation to the clinical course of multiple sclerosis have not been reported. In the present study, both lymphoblastic transformation and migration inhibitory factor assays were used, and results related to the temporal course of multiple sclerosis. Results of the present investigation show that cell-mediated hypersensitivity to myelin basic A1 protein is most significant during exacerbations of multiple sclerosis. Responses obtained employing either the lymphoblastic transformation or migration inhibitory factor assay were equally significant. The results support the hypothesis that a factor suppressing deoxyribonucleic acid synthesis is present in multiple sclerosis and is inhibited by the use of steroids.

The macrophage migration inhibitory factor (MIF) assay and the lymphoblastic transformation (LBT) technique were utilized simultaneously to measure immune responses to peptide Y, the 17 amino acid C-terminal fragment of basic myelin protein, in patients with multiple sclerosis (MS). Ten normals and 67 MS patients from the Montreal Neurological Hospital and affiliated institutions were examined. A prospective attempt was made to correlate the measured responses with phasic clinical activity of the disease. The LBT results indicate some degree of cellular sensitization to peptide Y which parallels the clinical course of the illness, and resembles earlier positive findings obtained with the whole basic myelin protein molecule. These findings, however, are in contrast to a negative MIF response to the Y peptide used in the present study and further contrast the positive MIF results obtained earlier using the whole protein. It is not evident from the results of the present study whether sensitization may be of any pathogenetic significance, but the findings show that differing portions of the basic myelin protein molecule may selectively stimulate specific lymphokine elaboration by sensitized lymphocytes.

It was found that the rabbit P2 protein contains cysteine (2 mol/mol protein), as well as 3 mol of methionine and 2 mol of tryptophan; histidine is absent. The three methionine residues are positioned in the vicinity of the NH2-terminal region as shown by isolation of a large peptide (98 residues), containing the COOH-terminal region, following cleavage with CNBr. Two tridecapeptides (CN2 and CN3) were also isolated from the CNBr digest, one of which contained a cysteine residue, while the other occupies the NH2-terminus since it failed to give a dansylated amino acid. Together with these three peptides, an octapeptide (CN4) was isolated, thus accounting for the three methionyl residues having linkage positions of Met-Lys, Met-Lys, and Met-Val.

Typical experimental allergic orchitis (EAO) and aspermatogenesis were successfully transferred to strain 13 guinea pigs with peritoneal exudate and lymph node cells from male and female donor guinea pigs (lacking detectable antibody) previously sensitized with 9 mug of highly purified GP1 glucoprotein isolated from the sperm acrosome. Attempts to transfer the disease with circulating antibody from hyperimmunized animals were not successful. These studies support a cell-mediated basis for the immunopathologic events in EAO.