Immunochemical and biochemical studies demonstrating the identity of a bovine spinal cord protein (SCP) and a basic protein of bovine peripheral myelin (BF)

In situ hybridization study of myelin protein mRNA in rats with an experimental diabetic neuropathy

Distribution of protein zero (P0) and myelin basic protein (MBP) mRNAs in the sciatic nerve from rats with alloxan-induced diabetes was analyzed at two different time points using in situ hybridization. Some animals of each diabetic group were treated with insulin. Densitometric quantitation of silver clusters revealed that 5 weeks after diabetes induction P0 mRNA only is significantly increased, while at 14 weeks both P0 and MBP mRNA contents are markedly higher than controls. Insulin treatment normalizes glycemia levels and slightly counteracts increased P0 mRNA at both stages of diabetes. An increase in MBP mRNA is observed in chronic diabetic animals only, and is unaltered by the normoglycemic effect of insulin. The increased transcript levels of P0 and MBP suggest that Schwann cells can modulate gene expression of myelin-specific proteins in response to diabetic-induced metabolic derangement. Such a change may represent a higher turnover of myelin proteins as an attempt by the Schwann cells to repair the diabetes-induced nerve damage. The observed pattern of transcript amount is only slightly influenced by insulin treatment.

Micropurification of two human cerebrospinal fluid proteins by high performance electrophoresis chromatography

Using C8 reversed-phase HPLC in conjunction with sodium dodecyl sulfate-polyacrylamide gel electrophoresis, we have fractionated proteins contained in human CSFs obtained from patients with schizophrenic disorders. When these proteins were electrophoretically blotted onto polyvinylidene difluoride membrane for direct N-terminal amino acid sequencing, several CSF proteins were identified; these included albumin, transferrin, apolipoprotein A-I, beta 2-microglobulin, and prealbumin. We have also identified two structurally related human CSF proteins designated cerebrin 28 (M(r) 28,000) and cerebrin 30 (M(r) 30,000) that have an N-terminal amino acid sequence of NH2-APPAQVSVQPNF and NH2-APEAQVSVQPLFXQ, respectively. Comparison of these sequences with existing database at Protein Identification Resource (R 32.0), GenBank (R 72.0), SWISS-PROT (R 22.0), and EMBL (R 31.0) indicated that they are unique proteins. These proteins were subsequently purified by high performance electrophoresis chromatography (HPEC) using an Applied Biosystems 230A HPEC system. A specific polyclonal antibody was prepared and an ELISA was established for cerebrin 30. It was noted that HPEC is a powerful tool to purify microgram quantities of proteins from human, rabbit, and rat CSFs. Using such a system, we have been able to micropurify as many as 10 proteins simultaneously in a single experiment because the elution of proteins occurred strictly according to their molecular weights. More importantly, we routinely obtained a recovery of > 90%. The potential use of this technology for micropurification of proteins was discussed.

Immunoassay of P2 protein in cerebrospinal fluid in neurological disorders

Cerebrospinal fluid samples were obtained at lumbar puncture from 53 patients with a wide variety of neurological disorders. Cerebrospinal fluid samples were tested for the presence of P2 protein, a constituent of myelin, with an enzyme linked immunosorbent assay technique using a specific polyclonal antibody. High concentrations of P2 in the cerebrospinal fluid paralleled a raised IgG index (clearance ratio), the presence of oligoclonal bands, as well as raised white cell counts or depressed albumin:IgG ratios. Twenty one patients had been diagnosed as having definite or probable multiple sclerosis and the remaining 32 had other conditions. Of the 13 patients with high positive P2, 12 (92%) were in the multiple sclerosis category; of the 40 patients with low (12) or undetectable (28) P2 concentrations, only nine (23%) were diagnosed as having multiple sclerosis. In this patient population the presence of high immunoreactive P2 concentrations in cerebrospinal fluid was closely associated with evidence of intrathecal immunoglobulin synthesis and with the clinical diagnosis of multiple sclerosis. On this basis it is suggested that immunoassay of P2 concentration in the cerebrospinal fluid may be of potential value in the investigation of patients with demyelinating disorders.

Bovine P2 myelin basic protein crystallizes in three different forms

P2 protein is a minor component of the myelin membrane. We have crystallized this protein for high-resolution crystallographic study. Three crystal morphologies are available. Two of them are from ammonium sulfate, and one is from polyethyleneglycol (PEG). The unit cell of the most suitable crystals from PEG 4000 has the dimensions a = 91.3 A, b = 99.8 A, c = 56.0 A; is of space group P2(1)2(1)2(1); and contains up to four molecules per asymmetric unit. The limit of resolution is 2.7 A.

Crystallization of P2 myelin protein

Single crystals of bovine P2 myelin protein have been grown in polyethylene glycol 4000 by the hanging-drop vapor diffusion method. Crystals belonging to space group P2(1)2(1)2(1) with cell dimensions a = 91.8 A, b = 99.5 A, c = 56.5 A (1 A = 0.1 nm). The diffraction pattern extends to better than 2.3 A resolution.

The secondary structure of myelin P2 protein derived by secondary structure prediction methods, circular dichroism, and 400-MHz 1H-NMR spectroscopy: implications for tertiary structure

The various methods used to study the secondary and tertiary structure of myelin P2 protein, and one of its peptides (CN1), in aqueous solution, indicate that the native protein contains a significant fraction of alpha-helix, suggesting that the current prediction of an all-beta tertiary structure requires revision.

Cellular hypersensitivity to nervous antigens in Guillain-Barré syndrome

Cell-mediated immune responses to various nervous antigens were examined in 12 cases of Guillain-Barré syndrome (GBS), 24 cases of noninflammatory peripheral neuropathy (NIPN), and 18 cases of degenerative disorders of central nervous system (CNSDD), using the lymphocyte-transformation technique. Cellular hypersensitivity to bovine P2 protein (P2) and a synthetic peptide, SP66-78, corresponding to the residues 66-78 of P2, was detected in about two-thirds of GBS cases, especially in the active or improving stages, but not in NIPN and CNSDD. The lymphocytes sensitized to these nervous antigens might play an important role in the pathogenesis of GBS.

One-way humoral immune cross-reactivity between bovine spinal cord protein and bovine myelin basic protein

Whether bovine myelin basic protein (BP) and bovine spinal cord protein (SCP) cross-react at the humoral immune level was assessed with a sensitive solid-phase enzyme immunoassay. We found that a hyperimmune anti-SCP serum reacted strongly with SCP and cross-reacted nearly as well with BP. A hyperimmune anti-BP serum reacted only with BP. Antigenic competition analysis revealed that SCP and BP both inhibited binding of the hyperimmune anti-SCP serum to solid-phase adsorbed SCP and BP, while only BP inhibited binding of the hyperimmune anti-BP serum to solid-phase adsorbed BP. Finally, BP cross-reactivity antibodies were present in early bleedings from rabbits immunized with SCP that had been passed through an anti-BP immunosorbent column. These results clearly show there is a one-way humoral immune cross-reactivity between SCP and BP which goes in the direction of SCP to BP.

Ultrastructural localization of P2 protein in actively myelinating rat Schwann cells

The myelin specific protein, P2, was localized immunocytochemically in electron micrographs of 4-day-old rat peripheral nerve by a preembedding technique. P2 staining was restricted to Schwann cells that had established a one-to-one relationship with an axon. P2 antiserum produced a diffuse staining throughout the entire cytosol of myelinating Schwann cells. In addition, the cytoplasmic side of Schwann cell plasma membranes and the membranes of cytoplasmic organelles that were exposed to cytosol were stained by P2 antiserum. This cytoplasmic localization of P2 protein is similar to that described for soluble or peripheral membrane proteins that are synthesized on free ribosomes. P2 antiserum stained the cytoplasmic side of Schwann cell membranes that formed single or multiple loose myelin spirals around an axon. In the region of the outer mesaxon, P2 antiserum stained the major dense line of compact myelin. These results demonstrate that P2 protein is located on the cytoplasmic side of compact myelin membranes and are consistent with biochemical studies demonstrating P2 to be a peripheral membrane protein.

Degradation of bovine P2 protein by bovine brain cathepsin D

Bovine brain cathepsin D cleaved bovine P2 protein to produce three major and several minor peptides. The major P2 peptides formed were shown by amino acid analysis and partial sequencing to be peptides 17-54, 20-58 and 65-131 with the latter predominating. In preliminary experiments, P2 peptide 65-131 did not induce experimental allergic neuritis in Lewis rats in equimolar amounts to the neuritogenic P2.

A general model of the P2 protein of peripheral nervous system myelin based on secondary structure predictions, tertiary folding principles, and experimental observations

The amino acid sequence of the P2 protein of peripheral myelin was analyzed with regard to regions of probable alpha-helix, beta-structure, beta-turn, and unordered conformation by means of several algorithms commonly used to predict secondary structure in proteins. Because of the high beta-sheet content and virtual absence of alpha-helix shown by the circular dichroic spectra of the protein, a bias was introduced into the algorithms to favor the beta-structure over the alpha-helical conformation. In order to define those beta-sheet residues that could lie on the external hydrophilic surface of the protein and those that could lie in its hydrophobic interior, the predicted beta-strands were examined for charged and uncharged amino acids located at alternating positions in the sequence. The sequential beta-strands in the predicted secondary structure were then ordered into beta-sheets and aligned according to generally accepted tertiary folding principles and certain chemical properties peculiar to the P2 protein. The general model of the P2 protein that emerged was a "Greek key" beta-barrel, consisting of eight antiparallel beta-strands with a two-stranded ribbon of antiparallel beta-structure emerging from one end. The model has an uncharged, hydrophobic core and a highly hydrophilic surface. The two Cys residues, which form a disulfide, occur in a loop connecting two adjacent antiparallel strands. Two hydrophilic loops, each containing a cluster of acidic residues and a single Phe, protrude from one end of the molecule. The general model is consistent with many of the properties of the actual protein, including the relatively weak nature of its association with myelin lipids and the positions of amino acid substitutions. Alternative beta-strand orderings yield three specific models having different interstrand connections across the barrel ends.

P2 protein in oligodendrocytes and myelin of the rabbit central nervous system

P2 protein, a myelin-specific protein, was detected immunocytochemically and biochemically in rabbit central nervous system (CNS) myelin. P2 protein was synthesized by rabbit oligodendrocytes and was present in varying amounts throughout the rabbit CNS. Comparison of P2 and myelin basic protein (MBP) stained sections revealed that P2 antiserum did not stain all myelin sheaths within the rabbit CNS. The proportion of myelin sheaths stained by P2 antiserum and the amount of P2 detected biochemically were greater in more caudal regions of the rabbit CNS. The highest concentration of P2 protein was found in rabbit spinal cord myelin, where P2 antiserum stained the majority of myelin sheaths. P2 protein was barely detectable biochemically in myelin isolated from frontal cortex, and in sections of frontal cortex only occasional myelin sheaths reacted with P2 antiserum. These results suggest the the regional variations in the amount of P2 protein are dut to regional differences in the number of myelin sheaths that contain P2 protein. P2 protein was detected immunocytochemically and biochemically in rabbit sciatic nerve myelin. Immunocytochemically, P2 antiserum only stained a portion of the myelin sheaths present. The myelin sheaths not reacting with P2 antiserum had small diameters and represented less than 10% of the total myelinated fibers.

Basic proteins of rodent peripheral nerve myelin: immunochemical identification of the 21.5K, 18.5K, 17K, 14K, and P2 proteins

Proteins in peripheral nervous system and central nervous system myelin and homogenates of sciatic nerve and brain from young and adult mice and rats were characterized with affinity-purified anti-P2 and anti-myelin basic protein sera after electrophoretic transfer from sodium dodecyl sulfate-polyacrylamide gels to nitrocellulose sheets. Using this method we have identified a component of rodent peripheral nervous system myelin as P2 protein. Peripheral nervous system myelin also showed the presence of four basic proteins in addition to P2 protein. These were found to be analogous to the 14, 17, 18.5, and 21.5K species found in the central nervous system myelin. A number of high-molecular-weight proteins were also detected with anti-myelin basic protein serum in peripheral nervous system, as well as central nervous system myelin. In addition, we report the presence of a high-molecular-weight P2 cross-reactive protein in rodent brain stem homogenates, but not in central nervous system myelin. Key Words: Basic proteins--PNS myelin--CNS myelin--Immunocharacterization. Greenfield S. et al. Basic proteins of rodent peripheral nerve myelin: Immunochemical identification of the 21.5K, 18.5K, 17K, 14K, and P2 proteins.

Neuritogenic determinant of bovine P2 protein in peripheral nerve myelin

Experimental allergic neuritis (EAN) is an experimentally produced demyelinating disease of peripheral nervous system. Several peptides of bovine P2 protein were tested for neuritogenic activity in Lewis rats. The hexacosapeptide CiT4 (residues 53--78 of bovine P2 protein) showed the highest neuritogenic activity among the peptides tested. The nonapeptide (residues 70--78) and the tridecapeptide (residues 66--78) were synthesized using the liquid phase peptide synthesis technique. The tridecapeptide showed mild, but definite activity in inducing EAN in the rats, while the nonapeptide was inactive. The localization of the neuritogenic determinant of bovine P2 protein in Lewis rats is discussed.

Conformation of bovine nerve root P2 protein: characteristics of the molecule from circular dichroism spectra

Circular dichroism (CD) was used to study the conformations of bovine nerve root P2 basic protein, its reduced and carboxymethylated derivative (RCM-P2), and its large cyanogen bromide fragment (CN1). Data in the far UV show that both the parent protein and RCM-P2 have conformations dominated by a large amount of beta structure. However, the CN1 peptide appears to exist in a largely unordered conformation. Since CN1 lacks short (20 residue) amino- and carboxy-terminal segments of the P2 protein, the spectral data suggest that these regions are important for determining and/or maintaining folding of the P2 protein in aqueous solutions. The P2 protein was found to have a distinctive CD spectrum in the near UV. The characteristics of molar ellipticities indicate that the spectrum contains significant contributions from tyrosine residues, and that these contributions suggest different environments for the two tyrosines in P2 protein. Both environments depend on protein conformation, since CD side chain absorptions are lost when P2 protein is denatured with 5 M urea.

A comparison of demyelinating and myelination-inhibiting factor induction by whole peripheral nerve tissue and P2 protein

Sera from rabbits sensitized with whole bovine spinal roots demyelinated and inhibited myelination in both peripheral and central nervous system tissue cultures. Antisera directed against the peripheral nerve myelin basic protein, P2, demonstrated no antimyelin activity in vitro. These results suggest that demyelinating and myelination-inhibiting factors are directed against some peripheral nerve component(s) other than the P2 protein.

Structure of bovine P2 basic protein: sequence of a carboxyterminal segment that is a neuritogen in rabbits

The sequence of the carboxyterminal 18 amino acids released by cyanogen bromide digestion of the bovine P2 protein was determined. It has several interesting structural and immunological properties. It contains the only two half-cystines in the molecule that have the capacity to form an intrachain disulfide bond. Using the rabbit as a test animal, this carboxyterminal peptide was capable of producing experimental allergic neuritis. The sequence of this peptide is Val-Val-Glu-Cys-Lys-Met-Lys-Asp-Val-Val-Cys-Thr-Arg-Ile-Tyr-Glu-Lys-Val.

The protein antigens of peripheral nerve myelin

Peripheral nervous system (PNS) tissue contains a variety of proteins, lipids, and carbohydrates that may serve as immunogens in proving immune responses, as antigens participating in immunological reactions, or as both types of agents. Three proteins P0, P1, and P2, account for approximately 70% of PNS myelin proteins. P0 is the major PNS myelin protein and is restricted to the PNS. P1 is similar to, if not identical with, myelin basic protein, the component of central nervous system myelin which induces experimental allergic encephalomyelitis. P2 has neuritogenic properties for inducing experimental allergic neuritis and may be involved in immune-mediated PNS myelin injury in humans. The complete amino acid sequence for P2 has recently been delineated, and its neuritogenic, immunogenic, and antigenic features can now be further characterized.

Bovine peripheral nervous system myelin P2 protein: chemical and immunological characterization of the cyanogen bromide peptides

Cleavage of bovine P2 protein by cyanogen bromide (CNBr) produced peptide fractions CN1, CN2, and CN3 which were isolated by gel filtration chromatography. CN2 was found to contain two NH2-terminals (lysine and valine) and accounted for both of the cysteine residues of P2. When reduced carboxymethylated P2 (RCM-P2) was digested with CNBr, peptides CN1 and CN3 were obtained as were (1) a peptide with NH2-terminal lysine (Lys) that contained no homoserine and only one cysteine residue and (2) a peptide with NH2-terminal valine (Val) that was co-eluted with CN3. These data and the chemical characterization of all the CNBr peptides obtained from P2 and RCM-P2 suggest that isolated P2 protein has a structure composed of the CNBr peptides in the order CN3-CN1-CN2(Val)-CN2(Lys) with an intrachain disulfide bond between the cysteine residues located in the two constituent peptides of CN2, CN2(Lys) and CN2(Val). To locate the neuritogenic region(s) within the P2 protein structure, CN1, CN2, and CN3 were tested for the ability to induced experimental allergic neuritis (EAN) in Lewis rats. The disease-inducing sites of P2 protein were found only in CN1; neither CN2 nor CN3 produced disease. EAN induced by CN1 was comparable to that induced with P2 protein as determined by disease onset, clinical symptoms, and histologic lesions.

Bovine P2 protein: sequence at the NH2-terminal of the protein

Sequence data from key fragments of the P2 protein established the order of cyanogen bromide (CNBr) peptides in the structure of the protein and the primary structure for approximately one-half of the molecule. Data were obtained from the three tryptic peptides of blocked NH2-terminal CNBr peptide (CN3), the large CNBr peptide of P2 protein (CN1), and a fragment obtained from P2 by cleavage at tryptophan with 2-(2-nitrophenylsulfenyl)-3-methyl-3'-bromoindolenine. This last fragment was found to contain an over-lapping sequence that proved the juxtaposition of CN1 and CN3 in P2 protein. Thus, based on this fact and the characteristics of the CNBr peptides, the P2 structure is composed of CNBr peptides in the order: CN3-CN1-CN2(Val)-CN2(Lys). A comparison was made between the partial sequence of P2 protein and the equivalent portion of the structure of bovine myelin basic protein. The structures of these two proteins were found to be distinctly different although certain similarities are found.

Evidence that the bovine spinal cord protein is not an intrinsic component of peripheral myelin

Bovine spinal cord protein from peripheral nerve (BSCP-PN) was detected in the soluble fraction of the initial 0.8 M sucrose homogenate of bovine peripheral nerves by immunodiffusion analyses and by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The BSCP-PN in the soluble fraction of the 0.8 M sucrose homogenates was 25% of the BSCP-PN found in the soluble fraction of 0.3 M NaCl homogenates of peripheral nerve. BSCP-PN was also identified in purified bovine peripheral nerve myelin by immunodiffusion analyses and by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Densitometry data indicated that the BSCP-PN in myelin decreased from 25% of the total protein to approximately 8% when myelin was extracted with 0.3 M NaCl or 0.05 M HCl. The protein that remained in the BSCP-PN band of the NaCl-extracted myelin was identified as the periodic acid-Schiff II glycoprotein of peripheral myelin. Basic proteins such as BSCP-PN or lysozyme bound to myelin and to NaCl-extracted myelin when they were added to homogenates of myelin in 0.8 M sucrose. Pepsin, an acidic protein, did not bind to myelin under the same conditions. The results suggest that in 0.8 M sucrose, positively charged BSCP-PN released from the cytoplasm by homogenization binds to negatively charged myelin; thereafter, the BSCP-PN-myelin complex remains intact until it is dissociated in media of sufficiently high ionic strength. This interpretation is consistent with the immunohistological studies which demonstrated that BSCP-PN was not in the myelin sheath but was clearly localized in axons and in, or adjacent to, the Schwann cell basement membrane.

Experimental allergic neuritis in the Lewis rat: characterization of the activity of peripheral myelin and its major basic protein,P2

Experimental allergic neuritis has been produced in the inbred Lewis rat in the absence of experimental allergic encephalomyelitis (EAE) using bovine intradural root myelin. The lack of EAE is probably because P1 is only weakly encephalitogenic in the rat. One of the basic proteins of bovine peripheral myelin, P2, was isolated and demonstrated to be pure by amino acid analysis and SDS PAGE. It was found to have a molecular weight of 15,400 and contained 4 mol 1/2-cystine/mol. This P2 was found to be highly neuritogenic and is probably the sole neuritogenic antigen in this system. The successful demonstration of its neuritogenicity must be due in large part to the use of the inbred Lewis rat and bovine P2, but an explanation could also involve the omission of denaturing organic solvents, the prevention of oxidative denaturation and presumably the fact that any changes which may occur are not sufficient to prevent recognition of the active site by the immune system of the inbred Lewis rat. P2 was neuritogenic down to 5 micrograms/animal. Its activity was enhanced by but not dependent on the presence of Mycobacterium in the adjuvant. This suggested that release of P2 could possibly break tolerance and produce an auto-immune disease such as the Guillain--Barre syndrome.

Bovine-derived spinal cord protein (SCP) protects guinea pigs from experimental allergic encephalomyelitis (EAE) - a confirmatory report

An axonally localized, non-encephalitogenic protein derived from bovine spinal cord can protect guinea pigs from EAE following challenge with bovine myelin basic protein. Protection from neurologic signs is significant although CNS pathology is present. The protective regimen apparently varies depending upon the species and strain of animal; this specific requirement may account for a previous negative report.