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G J Markelonis

Publications and source records attributed to G J Markelonis.

At least 19 recordsLinked to original sources
PubMed1995

Acidic pH rapidly increases immunoreactivity of glial fibrillary acidic protein in cultured astrocytes.

Neuroepithelial progenitor cells from forebrains of newborn rat pups develop into "mature" astrocytes in an epidermal growth factor-containing medium free of serum (Von Visger et al: Exp Neurol 128:34, 1994). Eight-week-old "mature" astrocyte cultures on poly-L-lysine-coated dishes were exposed to an acidic medium (pH 5.8-6.0) for 2-6 h. Immunoreactivity for glial fibrillary acidic protein (GFAP) dramatically and rapidly increased; this immediate increase was not affected by pretreatment with cycloheximide. In further experiments we found that the increase in GFAP was undiminished for 24-48 h after the acid-treated astrocytes were returned to normal growth medium. The Ca2+ channel antagonists nifedipine and diltiazem attenuated the increase in GFAP immunoreactivity. These results suggest that extracellular acidosis may produce a rapid increase in GFAP immunoreactivity in astrocytes independent of de novo protein synthesis, possibly by increasing intracellular levels of free Ca2+ ions.

Acidosis↗
PubMed1994

Differentiation and maturation of astrocytes derived from neuroepithelial progenitor cells in culture.

Neuroepithelial progenitor cells from striata of adult mice develop into either astrocytes or neurons when cultured in the presence of epidermal growth factor (B. A. Reynolds, and S. Weiss, Science 255: 1707-1710, 1992). We instituted primary cultures of such progenitor cells from forebrains of newborn rat pups in an epidermal growth factor-containing medium free of serum in order to study the development of astrocytes in culture. At 4-6 days, primary cultures consisted of floating clusters of proliferating cells which expressed nestin, a marker for neuroepithelial progenitor cells, the ganglioside GD3, and vimentin. When clusters were transferred to polylysine-coated dishes, cells attached to the substrate and began to express antigens characteristic of particular differentiated neurons, astrocytes, or oligodendrocytes within 2 weeks. In 4- to 6-week-old secondary cultures, levels of vimentin expression appeared to decrease within maturing astrocytes which had increased levels of glial fibrillary acidic protein. These results suggest that multipotential epidermal growth factor-progenitor cells can give rise to both neurons and macroglia of the adult central nervous system, and that maturation of the astrocytes in vitro may be occurring in a pattern similar to that seen in vivo. Furthermore, no glial fibrillary acidic protein-positive cells expressed the A2B5 antigen in the same cell indicating an absence of type-2 astrocytes.

Animals↗
PubMed1993

Effects of interleukin-1 beta and tumor necrosis factor-alpha on the expression of glial fibrillary acidic protein and transferrin in cultured astrocytes.

Recent evidence suggests that interleukin (IL)-1 and tumor necrosis factor (TNF) may play a role in astrogliosis following injury to the CNS. The short-term biochemical effects of these immune-related cytokines were determined on cultured rat polygonal and process-bearing astrocytes. Both IL-1 and TNF stimulated the rate of thymidine incorporation in polygonal astrocytes up to 137% and 215%, respectively, over the level observed in untreated controls. By contrast, thymidine incorporation was relatively unaffected by these cytokines in process-bearing astrocytes. The cytokines did not significantly affect the level of glial fibrillary acidic protein (GFAP) within polygonal astrocytes, even though they appeared to downregulate the expression of GFAP mRNA by as much as 62%. Both cytokines increased the intracellular expression of transferrin (Tf) within some polygonal astrocytes. In untreated control cultures, fewer than than 2% of polygonal astrocytes were immunoreactive for Tf. By contrast, approximately 30% of polygonal astrocytes treated with IL-1 or TNF-alpha became strongly immunoreactive for Tf. Neither IL-2 nor a number of other known growth factors appeared to alter the level of immunoreactive Tf in these cells. Process-bearing astrocytes were negative for Tf, regardless of the treatment used. Northern blot analysis demonstrated that the level of Tf mRNA in cultures of polygonal astrocytes increased 148% above the level observed in untreated controls following treatment with either IL-1 or TNF, whereas no change was observed following treatment with IL-2. These results suggest that increased levels of particular cytokines known to be present in injured CNS can produce pronounced biochemical alterations within a subtype of cultured astrocytes.

Animals↗
PubMed1992

Interleukin-1-beta and tumor necrosis factor-alpha increase peripheral-type benzodiazepine binding sites in cultured polygonal astrocytes.

Peripheral-type benzodiazepine binding sites (PTBBS) are markedly increased in the injured CNS. Astrocytes appear to be the primary cell type which express increased PTBBS. Because certain cytokines within the injured CNS are potent mitogens for astrocytes, we examined the effects of two such cytokines, interleukin (IL)-1 beta and tumor necrosis factor (TNF), on PTBBS in cultured astrocytes using [3H]Ro 5-4864 as the specific ligand. Purified cultures of either polygonal or process-bearing astrocytes were prepared from neonatal rat cerebral hemispheres. At a concentration of 1.8 nM, specific binding of the radioactive ligand to polygonal astrocytes reached equilibrium within 60 min and was half-maximal by 5-10 min. By contrast, specific binding to process-bearing astrocytes barely exceeded background levels. IL-1 and TNF increased PTBBS within polygonal astrocytes in both dose- and time-dependent manners. At 10-50 ng/ml, IL-1 beta and TNF-alpha elevated [3H]Ro 5-4864 binding in polygonal astrocyte cultures 65 and 87%, respectively, above the level in control cultures. However, no changes in PTBBS were seen within polygonal astrocytes after IL-2 treatment. Scatchard analysis of saturation binding experiments suggested that the increase in PTBBS promoted by TNF was due to an increased number of binding sites present in polygonal astrocytes and not due to an increase in receptor affinity. Binding data suggested that PTBBS within cultures of process-bearing astrocytes were virtually absent irrespective of the treatment. These in vitro data suggest that certain cytokines found in the injured brain may be involved in up-regulating PTBBS within a particular subtype of astrocyte.

Animals↗
PubMed1991

A neurite-promoting factor from muscle supports the survival of cultured chicken spinal motor neurons.

During embryonic development, spinal motor neurons require muscle-derived trophic factors for their survival and growth. We have recently isolated a protein from muscle that is not laminin but that still stimulates neurite outgrowth from embryonic neurons in culture. In the present study, we investigated whether this protein, which we refer to as muscle-derived neurite-promoting factor (NPF), could also promote the survival and growth of motor neurons in culture. Spinal motor neurons were isolated from 6-day-old chicken embryos by a metrizamide step-gradient centrifugation protocol. Most large cells (putative motor neurons) were found in the upper metrizamide fraction (0%-6.8% interface; fraction I). Motor neurons were identified by increased specific activity of choline acetyltransferase (CAT) and by their propensity to transport retrogradely either wheat germ agglutinin-horseradish peroxidase or the fluorescent dye, 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine per chlorate (diI), when those substances were injected into the target field. Labeled motor neurons were 2.6-fold enriched in fraction I and the specific CAT activity was 4.4-fold increased in fraction I as compared to unfractionated cells. When motor neurons were grown on muscle-derived NPF, the protein supported the survival of at least 21% of the neurons for as long as 6 days in culture. The protein showed no significant effect on either CAT specific activity or on high-affinity choline uptake by neurons. There was a substantial increase from 21% to 38% of the survival of motor neurons when a combination of muscle-derived NPF and laminin was used as the substrate. Muscle-derived NPF also promoted the survival of sensory neurons and sympathetic neurons in culture. Our results demonstrate that a neurite-promoting protein derived from muscle promotes both the survival and the outgrowth of neurites from cultured spinal motor neurons as well as from sensory and sympathetic neurons.

Acetylcholinesterase↗
PubMed1991

Immunocytochemical localization of mitochondrial malate dehydrogenase in primary cultures of rat astrocytes and oligodendrocytes.

To assess the oxidative metabolism of glial cells, we visualized mitochondrial malate dehydrogenase (mMDH) in purified cultures of neonatal rat polygonal and process-bearing astrocytes as well as in oligodendrocytes, using indirect immunofluorescence. Double immunofluorescent localization of rabbit anti-mMDH and either mouse monoclonal antiglial fibrillary acidic protein or anti-myelin basic protein demonstrated that both process-bearing astrocytes and oligodendrocytes showed uniformly intense anti-mMDH immunoreactivity in their cell bodies. However, immunoreactivity to mMDH among polygonal astrocytes varied from very weakly positive to intensely positive. Experiments with rhodamine 123, a mitochondrion-specific fluorochrome, indicated that polygonal astrocytes contain relatively similar numbers of mitochondria; this suggested that the variable intensities of anti-mMDH immunoreactivity observed did not result from differences in mitochondrial numbers. In cultures of polygonal astrocytes maintained in a chemically defined medium containing growth factors and hormones, or in complete culture medium containing 1mM N6, O2-dibutyryl adenosine 3',5'-cyclic phosphate, the resultant stellate astrocytes still showed their original variable levels of anti-mMDH immunoreactivity. This suggested that the mMDH distribution pattern did not depend on the degree of morphological differentiation. Furthermore, cultures of polygonal astrocytes isolated from four specific regions of neonatal rat brain showed variable but reproducible profiles of anti-mMDH immunoreactivity. Our results suggest that there may be an appreciable range in the level of oxidative metabolism among individual polygonal astrocytes in culture.

Animals↗
PubMed1988

A muscle-derived substrate-bound factor that promotes neurite outgrowth from neurons of the central and peripheral nervous systems.

The development and survival of spinal motor neurons depends upon muscle-derived trophic factors. Some circumstantial evidence suggested to us that the regulatory subunit of cyclic adenosine 3':5'-monophosphate-dependent protein kinase (cAMP-dPK)-type II might be involved in neuritic outgrowth from spinal neurons. In the present study, we tested a commercial preparation of cAMP-dPK for neurite-promoting activity. Commercial cAMP-dPK-type II from skeletal and cardiac muscles elicited a significant neurite outgrowth from cultured embryonic chicken neurons when the enzyme preparation was bound to polylysine-coated substrata; type I cAMP-dPK from skeletal muscle was ineffective. Neither cAMP-dPK-type I nor -type II had a significant effect on the survival of spinal neurons in culture. Type II cAMP-dPK also stimulated neurite outgrowth from chicken cerebral hemisphere neurons, dorsal root ganglionic neurons, ciliary ganglionic neurons, and rat sympathetic ganglionic neurons in culture. The neurite-promoting activity appears to reside in a contaminant of the preparation since neither the purified regulatory nor catalytic subunits of cAMP-dPK-type II had an effect on neurite outgrowth per se from cultured neurons and since neurite-promoting activity did not correlate with [3H]cAMP binding or cAMP-dependent kinase activity. The neurite-promoting protein was then partially purified from commercial cAMP-dPK-type II by gel filtration on Sephadex G-200 followed by ion-exchange chromatography on DE-52 cellulose. Sodium dodecyl sulfate gel electrophoresis of the active protein peak revealed a major protein band (MW 50 kDa) and several minor bands (e.g., MW 200 kDa, 52 kDa, 45 kDa). Also, immunoblot analysis and immunoprecipitation revealed that the partially purified neurite-promoting protein was distinct from laminin, heparan sulfate proteoglycan, nerve growth factor, neural cell adhesion molecule, and fibronectin. Furthermore, the neurite-promoting activity was not diminished by treatment with heparinase nor was it bound to heparin conjugated to Sepharose. Our results demonstrate that a protein unrelated to laminin or its associated macromolecules and which copurifies with the type II cAMP-dPK of striated muscle stimulates neurite outgrowth from neurons of the central and peripheral nervous systems.

Animals↗
PubMed1988

Immunocytochemical localization of transferrin and mitochondrial malate dehydrogenase in the developing nervous system of the rat.

Transferrin accumulates within neurons of the developing nervous system of humans, sheep, pigs and chickens. To assess the relationship of this accumulation with the ontogeny of oxidative metabolism, we studied the immunocytochemical localization of transferrin (Tf) and the mitochondrial form of malate dehydrogenase (mMDH) in developing neural tissues by the peroxidase-antiperoxidase method. Rabbit anti-rat Tf was obtained commercially and gave a single band of reaction product (MW = 80 kd) on Western blots. Antibodies to porcine heart mMDH were elicited in a rabbit. Western blot analysis showed that this anti-porcine mMDH antibody reacted with the mMDH from porcine, rat or avian tissue but not with the cytosolic MDH from pigs. Tf was first detected in rat brain neurons at about the 18th embryonic day and reached a peak at about the 6th postnatal day. All neurons were immunoreactive with large neurons throughout the brain showing a strong reaction for Tf. From this time onward, the level in brain neurons gradually decreased until adulthood. However, Tf immunoreactivity still remained strongly evident in capillary endothelial cells. The localization of Tf within rat spinal cord neurons peaked as early as the 1st postnatal day and remained elevated to the 6th postnatal day. By contrast, reactivity for Tf within dorsal root ganglia neurons was intense as early as the 18th embryonic day and diminished only gradually. Mitochondrial MDH, a marker for oxidative metabolism, appeared to reach a peak after the crest of intraneuronal Tf had been observed. For example, brain and spinal cord MDH immunoreactivity increased with intense staining in the cell bodies and fibers of neurons from the 6th to the 13th postnatal day; immunoreactivity gradually diminished into adulthood. The gradient of reactivity was low in some areas of the brain but more intense in areas containing large neuronal cell bodies such as the red nucleus. This occurred after the peak of intraneuronal Tf at day 6 and suggested a precursor-product relationship. By contrast, immunoreactivity for neuron-specific enolase, a glycolytic enzyme, showed a developmental pattern that differed from either Tf or MDH in that reactivity appeared later in development and was less intense. These data suggest that as cerebral metabolic rates begin to increase as early as 5-6 days after birth in the rat, an increase in mMDH occurs coincident with the onset of oxidative metabolism. Furthermore, this rise in intraneuronal mMDH follows the peak of intraneuronal Tf and suggests that Tf supplies the iron required for the synthesis of other mitochondrial ferroproteins.

Aging↗
PubMed1988

Immunocytochemical localization of aldolase in normal, denervated, and dystrophic chicken muscles.

To investigate whether immunocytochemical localization of muscle-specific aldolase can be used for fiber phenotype determination, we produced specific antibodies against the enzyme and studied its distribution in adult chicken skeletal muscles by indirect immunofluorescence microscopy. Monoclonal antibodies against the myosin heavy chains of fast-twitch (MF-14) and slow-tonic (ALD-58) muscle fibers were also used to correlate aldolase levels with the fiber phenotype. The goat anti-aldolase antibody was found to be specific for the A form of aldolase, as evidenced by sodium dodecyl sulfate gel electrophoresis, immunotitration experiments, and immunoblot analysis. The antibody reacted strongly with the fast-twitch myofibers of normal pectoralis and posterior latissimus dorsi muscles; the phenotype of these muscle fibers was confirmed by a positive immunofluorescent reaction after incubation with MF-14 antibody. By contrast, the slow-tonic myofibers of normal anterior latissimus dorsi, which react positively with ALD-58 antibody, reacted weakly with anti-aldolase antibodies. In denervated chicken muscles, reaction to anti-aldolase antibodies was markedly reduced in fast-twitch fibers, although reaction to MF-14 was not diminished. By contrast, in dystrophic muscle, fast-twitch fibers showed reduced reactivity to anti-aldolase and marked to moderate reduction in MF-14 reactivity. Our results show that: (a) in normal muscles, reactivity to anti-aldolase matches the phenotype obtained by using anti-fast or anti-slow myosin heavy chain antibodies, and therefore can serve to identify mature fibers as fast or slow; and (b) in denervated or dystrophic muscles, the intracellular expressions of aldolase and fast-twitch myosin heavy chains are regulated independently.

Animals↗
PubMed1988

Localization of transferrin within the developing vertebrate nervous system.

Transferrin is one of several serum proteins localized within neurons during development of the nervous system. The expression of transferrin receptors appears to precede the active accumulation of transferrin by neurons. The first cells immunoreactive for transferrin appear adjacent to the ventricles or to the central canal of the spinal cord. These cells then appear to migrate from this site. These neurons become progressively more immunoreactive for transferrin, attain a peak of reactivity and then lose their reaction to antitransferrin antibodies. Thus, a "window" of transferrin immunoreactivity is found. As neurons lose their reactivity to antitransferrin antibodies, glia and the walls of capillaries become positive. In the rat nervous system, the gradual decrease in intraneuronal transferrin is accompanied by an increase in mitochondrial malate dehydrogenase, an enzyme of the tricarboxylic acid cycle. Thus, the accumulation of transferrin appears to closely precede the ontogeny of oxidative metabolism in the brain. As transferrin appears transiently in all neurons, this protein may be involved in a number of other important developmental events such as the expression of dopamine D2 receptors and the period of "programmed" cell death in the spinal cord.

Animals↗
PubMed1987

Transferrin: assay of myotrophic effects and method for immunocytochemical localization.

1. Primary cultures of dissociated embryonic chicken skeletal muscle cells provide an ideal model for investigating the effects of growth factors such as Tf because these cells undergo a highly integrated pattern of differentiation and maturation. 2. The trophic effects of a growth factor such as Tf can be assessed on muscle cultures by the determination of such parameters as acetylcholinesterase and acetylcholine receptors. These proteins are specific to the cultured myotubes, appear in high levels following fusion of myoblasts into myotubes, and are relatively easy to assay. 3. Tf and other growth factors are internalized by a receptor-mediated mechanism (see Trowbridge et al. and Seligman and Allen, this volume). These growth factors can be localized to specific tissues by immunocytochemistry at the light or electron microscopic level. This information on cellular distribution could be very useful in assessing the pattern of growth and differentiation with regard to the particular growth factor under study.

Acetylcholinesterase↗
PubMed1986

Immunocytochemical distribution of transferrin and its receptor in the developing chicken nervous system.

Transferrin is the plasma protein responsible for iron transport in all vertebrates. While transferrin is known to have growth-promoting activity on a variety of cells in culture, the role of transferrin and its membrane receptor in neuronal development is unknown. Using antibodies to transferrin and transferrin receptors, we studied the immunocytochemical localization of transferrin and its receptor in developing chicken neural tissues by the peroxidase-antiperoxidase method. In 5-day-old embryonic brain, germinal cells of the ventricular zone showed a positive reaction for transferrin receptors but were negative for transferrin. By 6-7 days, transferrin-positive cells were seen in the inner layer of the ventricular zone and a few 'patches' of transferrin-positive cells were also seen in the adjacent area. By 10 days, large neurons throughout the brain were strongly positive for transferrin. By 11-16 days, all neurons in the brain showed a strong positive reaction for the protein. Thereafter, the transferrin-positive reaction became gradually weaker in neurons whereas the walls of blood capillaries showed a positive reaction for transferrin. In the adult brain, neurons showed very weak or negative staining. A similar staining pattern for transferrin was observed in the developing spinal cord and dorsal root ganglia (DRG). By 10-12 days, both spinal cord neurons and DRG neurons showed strong reactions for transferrin. Thereafter, the transferrin-positive reaction gradually diminished in older spinal cord neurons and completely disappeared from DRG neurons. Cultured cerebral hemisphere, spinal cord, and DRG neurons showed positive staining reactions for both transferrin and its receptor. Our results suggest that: transferrin is initially taken up by developing neurons from cerebrospinal fluid via receptor-mediated endocytosis; the accumulation of transferrin ultimately reaches a maximum level within immunoreactive neurons and then declines just prior to hatching; in contrast to other CNS neurons, DRG neurons accumulate transferrin only briefly and then become negative for transferrin by immunocytochemistry; and after closure of the blood-brain barrier, transferrin may reach neurons by transport across capillaries into the 'paravascular' spaces. In view of these results, transferrin may play some important but unrecognized role in early neuronal development in vivo as well as in vitro.

Animals↗
PubMed1986

Effects of cell division, cell density, and cyclic nucleotides on choline acetyltransferase activity in a cholinergic neuroblastoma cell line (S-20Y).

We investigated the effects of a number of experimental perturbations on choline acetyltransferase (ChAT) in a cholinergic mouse neuroblastoma cell line (S-20Y). ChAT specific activity increased by 4.5-fold during growth, suggesting that enzyme activity is dependent on increased cell density. This was confirmed by assessing enzyme activity at differential initial seeding densities. ChAT activity was also markedly enhanced by 1 mM dibutyryl cyclic-3',5'-AMP (dBcAMP), an effect that was blocked by cycloheximide. Confirmation of the dBcAMP effect was achieved with forskolin, a compound known to enhance intracellular cyclic AMP; forskolin (100 microM) caused a significant increase in ChAT activity. After a 20-h latent interval ChAT activity was also enhanced significantly by cytosine arabinoside. The common element in these diverse effects on ChAT activity may be cessation of cell division, although cell-cell interactions at the level of the cell membrane may also be important in the control of ChAT in S-20Y.

Animals↗
PubMed1985

Synthesis of the transferrin receptor by cultures of embryonic chicken spinal neurons.

We have purified a glycoprotein from chicken sciatic nerves, sciatin, which has pronounced trophic effects on avian skeletal muscle cells in culture. Recent studies have shown that sciatin is identical to the iron-transport protein, transferrin, in terms of its physicochemical structure, immunological reactivity, and biological activity. To determine whether transferrin is synthesized and released by neuronal tissue, we incubated cultures of dissociated chicken spinal neurons in a medium free of L-leucine containing either L-3H-amino acids or L-[14C]leucine and immunoprecipitated transferrin with highly specific antibodies. The radiolabeled protein precipitated by rabbit heteroclonal, goat heteroclonal, or mouse monoclonal antitransferrin antibodies increased in specific activity in a linear manner for at least 30 min. Synthesis of this protein was abolished by the presence of puromycin (20 micrograms/ml) or cycloheximide (10(-5) M). The disappearance of the radiolabeled protein from cells was linear with a half-life (t 1/2) of 8-10 h. When immunoprecipitates were separated by SDS gel electrophoresis, a prominent band corresponding to transferrin (Mr 84,000) was visualized by staining with Coomassie Blue. However, when such gels were fluorographed, no radioactivity was apparent in the transferrin region of the gel although a prominent radioactive band was visualized at an Mr of 56,000. The protein of Mr 56,000 was not simply a degradation product of transferrin because this particular protein band was not generated by incubating radiolabeled transferrin with unlabeled neuronal homogenates. The protein of Mr 56,000 was purified from embryonic chicken brain and spinal cord by immunoabsorption chromatography on mouse monoclonal antitransferrin IgG conjugated to Sepharose 4B followed by affinity chromatography on immobilized transferrin. The purified protein bound radioiodinated transferrin and was precipitated by rabbit anti-chicken transferrin-receptor antibodies. Furthermore, this receptor protein was found to be localized on the plasma membrane of dorsal root ganglion neurons by immunocytochemistry using the peroxidase-antiperoxidase technique, and by blocking experiments, which showed that antitransferrin receptor IgG could inhibit the binding of fluorescein-conjugated transferrin at 4 degrees C to cultured neurons in vitro. From these data, we conclude that transferrin is not synthesized by cultures of chicken spinal cord neurons, but that the receptor for transferrin is synthesized by these cultures and is precipitated by antitransferrin antibodies as an antigen-receptor complex.

Animals↗
PubMed1982

Chicken serum transferrin duplicates the myotrophic effects of sciatin on cultured muscle cells.

Sciatin, a glycoprotein purified from chicken sciatic nerves, has been shown to have trophic effects on chicken skeletal muscle cells in culture. Since we recently observed pronounced structural similarities between sciatin and chicken serum transferrin [Markelonis et al, 1982a], we decided to investigate the muscle growth-promoting activity of transferrin on cultured muscle cells. Serum transferrin was isolated by the same protocol used to purify sciatin, viz., affinity chromatography on concanavalin A-agarose followed by ion-exchange chromatography on DEAE cellulose. The serum protein recovered by this purification scheme was indistinguishable immunologically from sciatin as evidenced by a positive precipitin reaction against goat anti-sciatin serum on double immunodiffusion in agar. Purified serum transferrin had myotrophic effects identical to those of sciatin when added to skeletal muscle cells in vitro. For example, even when chicken embryo extract--a constituent normally required for chicken muscle cell differentiation in vitro--was omitted from culture medium, either serum transferrin or sciatin promoted myogenesis in culture as measured by a stimulation of the fusion index. Furthermore, both proteins caused a significant increase in the level of protein synthesis, the number of acetylcholine receptors and the activity of acetylcholinesterase in treated muscle cultures. By contrast, commercially obtained ovotransferrin (conalbumin) or FeSO4 (100 microM) were unable to fully support myogenesis of skeletal muscle in vitro if embryo extract was omitted from the culture medium. From these data, we conclude that the neuronal myotrophic protein sciatin is both structurally and biologically related to serum transferrin. Furthermore, we suggest that sciatin may represent a neuronal form of this iron-transport protein.

Animals↗
PubMed1982

Sciatin is a transferrin-like polypeptide.

Sciatin, an acidic glycoprotein from chicken sciatic nerve, the myotrophic effects on avian skeletal muscle cells in culture. As sciatin was found to have certain structural similarities to transferrin, we further investigated the physiochemical characteristics of sciatin in order to determine the relationship between these two proteins. Sciatin was found to be strikingly similar to ovotransferrin in amino acid composition. In addition, amino acid sequence analysis revealed that sciatin and ovotransferrin and identical amino-terminal sequences for a t least the first 20 amino acid residues. Chicken ovotransferrin, but not human serum transferrin, cross-reacted with rabbit antisciatin antibodies upon rocket immunoelectrophoresis and double immunodiffusion in agar. In addition, in the presence of bicarbonate, sciatin bound approximately 2 mol ferrous iron/mol protein. Using the purification procedure developed for sciatin, we purified a protein from chicken serum that cross-reacted with antisciatin serum, migrated at a position identical to that of sciatin or ovotransferrin on two-dimensional gel electrophoresis, had an amino composition very similar to ovotransferrin and sciatin, and had myotropic effects on cultured muscle cells. From these data, we conclude that sciatin is a growth-promoting polypeptide closely related in structure to transferrin.

Amino Acid Sequence↗