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  • 1
    Electronic Resource
    Electronic Resource
    Characterization of gp93, a Novel, Highly Heterogeneous Glycoprotein Present in Growth Cone Membranes (1994)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 63 (1994), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: gp93 was first described in growth cones from fetal rat brain as a 90–97-kDa glycoprotein family that binds wheat-germ agglutinin and consists of at least 12 different isoelectric variants (pl range ∼4.9–6.4). Of particular interest is that different sets of gp93 variants are expressed in growth cones isolated from different brain regions. The preparation of a polyclonal antibody to gp93 allowed further characterization of this glycoprotein. The carbohydrate groups of gp93 were partially characterized by digestion with different glycosidases. The results indicate that most or all oligosaccharide units are N-linked (asparagine-linked) and contain sialic acid. Two-dimensional polyacrylamide gel electrophoresis and western blot with anti-gp93 show that deglycosylated gp93 is an only slightly heterogeneous polypeptide of 66 kDa, indicating that gp93 heterogeneity is due, primarily or exclusively, to differential glycosylation. Analysis of the tissue distribution in fetal rat showed gp93 to be highly enriched in the brain. Immunoblots and immunostaining of cross sections of developing cerebellum revealed that gp93 is developmentally regulated in this tissue, associated primarily with growing parallel fibers and Purkinje dendrites. Immunostaining of neurons in culture shows significant amounts of gp93 in elongating neurites and growth cones. Our results indicate that gp93 is a developmentally regulated glycoprotein of the brain that is most prominent in growth cones and growing neurites and that appears to be glycosylated differentially by different neurons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.1994.63031150.x
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  • 2
    Electronic Resource
    Electronic Resource
    Arachidonic Acid Turnover and Phospholipase A2 Activity in Neuronal Growth Cones (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 60 (1993), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: We analyzed de novo synthesis and local turnover of phospholipids in the growing neuron and the isolated nerve growth cone. The metabolism of phosphatidylinositol (PI) was studied with regard to the incorporation of saturated and unsaturated fatty acids and inositol. A comparison of de novo phospholipid synthesis in the intact neuron (whole brain, cell cultures) versus local turnover in isolated growth cone particles (GCPs) from fetal rat brain revealed different incorporation patterns and, in particular, high arachidonic acid (AA) turnover in PI of GCPs. These observations, together with elevated levels of free AA (2.5% of total AA content) in GCPs, demonstrate the predominance of acylation/deacylation in the sn-2 position of PI. GCP phospholipase A2 (PLA2) activity was demonstrated using [3H]-or [14C]AA-phosphatidylcholine (PC) or -PI as the substrate in vitro and GCPs or a cytosolic GCP extract as the source of enzyme. In contrast to PC, which is hydrolyzed very slowly, PI is a very good GCP PLA2 substrate. PLA2 activity is much higher in GCPs than that of phospholipase C, as demonstrated by the comparison of AA and inositol turnover, by the low levels of 1,2-diacylglycerol generated by GCPs, and by the resistance of AA release to treatment of GCPs with RHC-80267, a specific inhibitor of diacylglycerol lipase. The predominance of PLA2 activity in GCPs raises questions regarding its regulation and the functional roles of PI metabolites, especially lysocompounds, in growth cones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1993.tb03263.x
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  • 3
    Electronic Resource
    Electronic Resource
    Gangliosides and Other Lipids of the Growth Cone Membrane (1988)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 51 (1988), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Growth cone membranes, derived from growth cone particles isolated from 16- to 18-day-old fetal rat brain, were found to be rich in overall lipid content with a lipid-to-protein ratio of 3.5. The phospholipid-to-cholesterol ratio indicated considerably less cholesterol than plasma membranes from mature neurons. All major classes of phospholipid were present in the usual proportions except sphingomyelin, which could not be detected. Gangliosides expressed in relation to protein were present at somewhat higher levels compared to previously reported values for synaptic plasma membranes (73 versus 44 μg/mg protein), but when related to phospholipid their level was well below that of the latter (26 versus 62 μg/mg phospholipid). The ganglioside pattern was generally similar to that of mature synaptic membranes except for the presence of relatively more GD3 and less GD1a, a phenomenon also observed in whole fetal brain of the same age. Several neutral glycosphingolipids were detected, glucosylceramide being the major one of this group. Their total level in growth cone membranes was roughly comparable to that of gangliosides, but unlike the latter their concentration in whole brain decreased with development. For comparison we analyzed the ganglioside composition of mixed membrane fractions from the same fetal brains and found no significant differences between these and growth cone membranes, suggesting that these glycoconjugates are not localized specifically in the growth cones. Neutral glycosphingolipids, on the other hand, appeared somewhat more concentrated in growth cones than in the mixed membranes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1988.tb04858.x
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  • 4
    Electronic Resource
    Electronic Resource
    The heterogeneous growth cone glycoprotein gp93 is identical to the signal regulatory protein SIRPα/SHPS-1/BIT (2003)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 86 (2003), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Growth cone gp93 is a highly heterogeneous membrane glycoprotein with an Mr of about 93 kDa. It was purified from adult rat brain and microsequenced. The sequences of four different peptide fragments of gp93 matched those of the ‘signal regulatory protein’ SIRPα (also known as SHPS-1, BIT or P84), an Ig superfamily member. SIRPα contains a cytoplasmic tail that is a tyrosine kinase substrate and binds the protein tyrosine phosphatase SHP-2. SIRPα and gp93 also were immunochemically cross-reactive. A PCR strategy was used to determine whether gp93/SIRPα heterogeneity in the brain depended upon the presence of different transcripts and, thus, sequence heterogeneity. However, we observed only a single full-length transcript. A short splice variant also was detected. These data identify gp93 as the Ig superfamily member SIRPα. Together with our previous results, the data also demonstrate that, in rat brain, gp93/SIRPα heterogeneity is the result of differential glycosylation (plus phosphorylation), rather than sequence heterogeneity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.2003.01810.x
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  • 5
    Electronic Resource
    Electronic Resource
    Anatomical distribution of glycoprotein 93 (gp93) on nerve fibers during rat brain development. (1999)
    Springer
    Cell & tissue research 297 (1999), S. 67-79 
    Details
    ISSN: 1432-0878
    Keywords: Key words Growth cones ; Glycoprotein ; gp93 ; Neuronal development ; Transplantation ; Axonal extension ; Rat (Fischer 344)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  Recent studies have implicated glycoconjugates on the membrane of growth cones as the necessary markers and intermediaries for axonal recognition, axonal motility, and pathway development. One such glycoconjugate, glycoprotein 93 (gp93), has been characterized, but the relative distribution of gp93 has yet to be described for the embryonic brain. In this study, the anatomical distribution of gp93 has been analyzed at embryonic day 15 (E15) and E18, and on postnatal day 3 in the rat by using a polyclonal gp93 antibody. Furthermore, fetal brain tissue transplanted into the adult rat eye has been tested for gp93 immunoreactivity, since central noradrenergic neurons in brainstem transplants are known to provide a continuous source of growing axons, even in adult tissue. In general, a greater abundance of gp93 immunoreactivity is apparent in the earlier embryonic stages (E15 and E18), whereas less is seen in the postnatal brain. The regions showing unique dispersal patterns of gp93 are the neuroepithelium, cerebral cortex, septo-hippocampal pathways, brainstem, and midbrain. This study has therefore focused on these areas and found implications for gp93 distribution appearing in the early development of specific neuronal pathways. Moreover, axons stain densely for gp93 within brain tissue transplants. The presence of gp93 in areas of extensive axonal outgrowth in the normal brain and in transplants suggests that this antibody is used as an early marker for axonal growth. Furthermore, gp93 might be used to map normal development in order to improve our understanding of diseases arising from developmental abnormalities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004410051334
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  • 6
    Electronic Resource
    Electronic Resource
    Substance P-like immunoreactivity in cultured spinal ganglia from chick embryos (1978)
    Springer
    Journal of neurocytology 7 (1978), S. 107-117 
    Details
    ISSN: 1573-7381
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The localization of substance P (SP) or a SP-like peptide in cultured spinal ganglia from chick embryos was studied by the indirect immunofluorescence technique. Ganglia from 8–16 days old chick embryos and from newly hatched chickens were cultured in a control medium or in the presence of nerve growth factor (NGF). Addition of colchicine and exposure to different explanted peripheral tissues were also tried. Ganglia from the younger embryos (8–12 days) cultured for 24 h with added NGF showed a weak SP-like immunoreactivity (SPLI) in some cell bodies and strong specific immunofluorescence in nerve fibres growing out from the ganglia. In spinal ganglia of the older embryos (14 and 16 days) and newly hatched chickens cultured with and without NGF the concentration of SPLI in the cell bodies was considerably higher. Addition of colchicine to spinal ganglia cultured 12 h in NGF-medium, resulted in retraction of nerve fibres and strongly fluorescent, expanded nerve fibres were observed in peripheral parts of the ganglia. Explants of skin placed near the spinal ganglia stimulated the outgrowth of fibres, some of them containing SPLI. A few fluorescent fibres were also seen within the skin explants. Also heart tissue explants stimulated outgrowth of nerve fibres, but innervation of these explants with SPLI-containing nerves could not be observed. Nerve fibre-extension from the spinal ganglia was not stimulated by spinal cord explants. The present results support the existence of SP-containing primary sensory neurons in chickens.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01213463
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  • 7
    Electronic Resource
    Electronic Resource
    Growth cone enrichment and cytoskeletal association of non-receptor tyrosine kinases (1995)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 30 (1995), S. 194-207 
    Details
    ISSN: 0886-1544
    Keywords: fetal rat brain ; tyrosine kinases ; c-src ; fyn ; lyn ; SH2 domain ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Fetal rat brain (E18) expresses at least three c-src-like, membrane-associated non-receptor tyrosine kinases: c-src, fyn, and lyn. c-src and fyn are the most abundant and are highly enriched in a subcellular fraction of nerve growth cones (GCPs). To study the cytoskeletal association of these tyrosine kinases, Triton X-100-resistant fractions were prepared from GCPs. All three non-receptor tyrosine kinases are associated with the cytoskeleton to a significant degree with the relative affinities: fyn 〉 c-src 〉 lyn. The binding is sensitive to ionic strength and to phosphotyrosine, but not to phosphoserine or phosphothereonine. To investigate the regulation of this association we used phosphatese inhibitors to increase phosphotyrosine levels in GCPs. This resulted in the release of c-src from the cytoskeleton. Under these conditions tyrosine phosphorylation was increased selectively in released c-src and primarily on tyrosine 527. Cytoskeletally bound c-src had a higher specific kinase activity than Triton X-100-soluble c-src. These findings indicate that src family members interact in a regulated manner with the cytoskeleton in non-transformed cells. This regulation is explained by a model in which c-src binds to the cytoskeleton via its SH2 domain and is released when phosphorylated tyrosine-527 binds to this domain intramolecularly, inhibiting kinase activity. © 1995 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970300304
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