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Neurite fasciculation mediated by complexes of axonin-1 and Ng cell adhesion molecule.

Kunz S, Spirig M, Ginsburg C, Buchstaller A, Berger P, Lanz R, Rader C, Vogt L, Kunz B, Sonderegger P - J. Cell Biol. (1998)

Bottom Line: In contrast, the axonin-1-NgCAM interaction excluded axonin-1/axonin-1 binding.These results and the examination of the coclustering of axonin-1 and NgCAM at cell contacts, suggest that intercellular contact is mediated by a symmetric axonin-12/NgCAM2 tetramer, in which homophilic NgCAM binding across the extracellular space occurs simultaneously with a cis-heterophilic interaction of axonin-1 and NgCAM.The enhanced neurite fasciculation after overexpression of NgCAM by adenoviral vectors indicates that NgCAM is the limiting component for the formation of the axonin-12/NgCAM2 complexes and, thus, neurite fasciculation in DRG neurons.

View Article: PubMed Central - PubMed

Affiliation: Institute of Biochemistry, University of Zurich, CH-8057 Zurich, Switzerland.

ABSTRACT
Neural cell adhesion molecules composed of immunoglobulin and fibronectin type III-like domains have been implicated in cell adhesion, neurite outgrowth, and fasciculation. Axonin-1 and Ng cell adhesion molecule (NgCAM), two molecules with predominantly axonal expression exhibit homophilic interactions across the extracellular space (axonin- 1/axonin-1 and NgCAM/NgCAM) and a heterophilic interaction (axonin-1-NgCAM) that occurs exclusively in the plane of the same membrane (cis-interaction). Using domain deletion mutants we localized the NgCAM homophilic binding in the Ig domains 1-4 whereas heterophilic binding to axonin-1 was localized in the Ig domains 2-4 and the third FnIII domain. The NgCAM-NgCAM interaction could be established simultaneously with the axonin-1-NgCAM interaction. In contrast, the axonin-1-NgCAM interaction excluded axonin-1/axonin-1 binding. These results and the examination of the coclustering of axonin-1 and NgCAM at cell contacts, suggest that intercellular contact is mediated by a symmetric axonin-12/NgCAM2 tetramer, in which homophilic NgCAM binding across the extracellular space occurs simultaneously with a cis-heterophilic interaction of axonin-1 and NgCAM. The enhanced neurite fasciculation after overexpression of NgCAM by adenoviral vectors indicates that NgCAM is the limiting component for the formation of the axonin-12/NgCAM2 complexes and, thus, neurite fasciculation in DRG neurons.

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Pertubation of neurite  fasciculation with species-specific  anti-NgCAM antibodies. Cultured  mouse DRG explants were infected  with the adenoviral vector AdCMVNgCAM. The explants were incubated in the presence of control  mouse IgG (a and d), monoclonal  anti-axonin-1 IgG X7C11 (b and e)  and the monoclonal mouse anti-NgCAM IgG 12-I-4E-311 (c and f).  NgCAM was detected on the cell  surface by indirect immunofluorescence as described in Fig. 11; a–c  represent fluorescence optics and  d–f the corresponding phase optics.  Bar, 100 μm.
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Figure 12: Pertubation of neurite fasciculation with species-specific anti-NgCAM antibodies. Cultured mouse DRG explants were infected with the adenoviral vector AdCMVNgCAM. The explants were incubated in the presence of control mouse IgG (a and d), monoclonal anti-axonin-1 IgG X7C11 (b and e) and the monoclonal mouse anti-NgCAM IgG 12-I-4E-311 (c and f). NgCAM was detected on the cell surface by indirect immunofluorescence as described in Fig. 11; a–c represent fluorescence optics and d–f the corresponding phase optics. Bar, 100 μm.

Mentions: Overexpression of axonin-1 resulted in a slightly reduced neurite fasciculation (Fig. 11, a, b, e, and f) compared with control explants treated with AdCMVlacZ (not shown) or without virus (Fig. 11, i–m). In contrast, overexpression of NgCAM resulted in strongly enhanced fasciculation (Fig. 11, c, d, g, and h). Quantitative analysis of the effects of axonin-1 and NgCAM overexpression on neurite fasciculation are summarized in Fig. 11 m (for details see Materials and methods). The effect of NgCAM overexpression on neurite fasciculation was blocked specifically by the addition of monoclonal anti-NgCAM IgG (Fig. 12, c and f) but not by control IgG (Fig. 12, b and e). The enhanced fasciculation observed with neurites overexpressing NgCAM can therefore be ascribed specifically to the enhanced NgCAM expression in the neuronal membrane. The observed effects of axonin-1 and NgCAM overexpression on neurite fasciculation are in accordance with the observation that NgCAM but not axonin-1 can efficiently mediate contact across the extracellular space in the context of heterooligomeric axonin-1–NgCAM complexes.


Neurite fasciculation mediated by complexes of axonin-1 and Ng cell adhesion molecule.

Kunz S, Spirig M, Ginsburg C, Buchstaller A, Berger P, Lanz R, Rader C, Vogt L, Kunz B, Sonderegger P - J. Cell Biol. (1998)

Pertubation of neurite  fasciculation with species-specific  anti-NgCAM antibodies. Cultured  mouse DRG explants were infected  with the adenoviral vector AdCMVNgCAM. The explants were incubated in the presence of control  mouse IgG (a and d), monoclonal  anti-axonin-1 IgG X7C11 (b and e)  and the monoclonal mouse anti-NgCAM IgG 12-I-4E-311 (c and f).  NgCAM was detected on the cell  surface by indirect immunofluorescence as described in Fig. 11; a–c  represent fluorescence optics and  d–f the corresponding phase optics.  Bar, 100 μm.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2132982&req=5

Figure 12: Pertubation of neurite fasciculation with species-specific anti-NgCAM antibodies. Cultured mouse DRG explants were infected with the adenoviral vector AdCMVNgCAM. The explants were incubated in the presence of control mouse IgG (a and d), monoclonal anti-axonin-1 IgG X7C11 (b and e) and the monoclonal mouse anti-NgCAM IgG 12-I-4E-311 (c and f). NgCAM was detected on the cell surface by indirect immunofluorescence as described in Fig. 11; a–c represent fluorescence optics and d–f the corresponding phase optics. Bar, 100 μm.
Mentions: Overexpression of axonin-1 resulted in a slightly reduced neurite fasciculation (Fig. 11, a, b, e, and f) compared with control explants treated with AdCMVlacZ (not shown) or without virus (Fig. 11, i–m). In contrast, overexpression of NgCAM resulted in strongly enhanced fasciculation (Fig. 11, c, d, g, and h). Quantitative analysis of the effects of axonin-1 and NgCAM overexpression on neurite fasciculation are summarized in Fig. 11 m (for details see Materials and methods). The effect of NgCAM overexpression on neurite fasciculation was blocked specifically by the addition of monoclonal anti-NgCAM IgG (Fig. 12, c and f) but not by control IgG (Fig. 12, b and e). The enhanced fasciculation observed with neurites overexpressing NgCAM can therefore be ascribed specifically to the enhanced NgCAM expression in the neuronal membrane. The observed effects of axonin-1 and NgCAM overexpression on neurite fasciculation are in accordance with the observation that NgCAM but not axonin-1 can efficiently mediate contact across the extracellular space in the context of heterooligomeric axonin-1–NgCAM complexes.

Bottom Line: In contrast, the axonin-1-NgCAM interaction excluded axonin-1/axonin-1 binding.These results and the examination of the coclustering of axonin-1 and NgCAM at cell contacts, suggest that intercellular contact is mediated by a symmetric axonin-12/NgCAM2 tetramer, in which homophilic NgCAM binding across the extracellular space occurs simultaneously with a cis-heterophilic interaction of axonin-1 and NgCAM.The enhanced neurite fasciculation after overexpression of NgCAM by adenoviral vectors indicates that NgCAM is the limiting component for the formation of the axonin-12/NgCAM2 complexes and, thus, neurite fasciculation in DRG neurons.

View Article: PubMed Central - PubMed

Affiliation: Institute of Biochemistry, University of Zurich, CH-8057 Zurich, Switzerland.

ABSTRACT
Neural cell adhesion molecules composed of immunoglobulin and fibronectin type III-like domains have been implicated in cell adhesion, neurite outgrowth, and fasciculation. Axonin-1 and Ng cell adhesion molecule (NgCAM), two molecules with predominantly axonal expression exhibit homophilic interactions across the extracellular space (axonin- 1/axonin-1 and NgCAM/NgCAM) and a heterophilic interaction (axonin-1-NgCAM) that occurs exclusively in the plane of the same membrane (cis-interaction). Using domain deletion mutants we localized the NgCAM homophilic binding in the Ig domains 1-4 whereas heterophilic binding to axonin-1 was localized in the Ig domains 2-4 and the third FnIII domain. The NgCAM-NgCAM interaction could be established simultaneously with the axonin-1-NgCAM interaction. In contrast, the axonin-1-NgCAM interaction excluded axonin-1/axonin-1 binding. These results and the examination of the coclustering of axonin-1 and NgCAM at cell contacts, suggest that intercellular contact is mediated by a symmetric axonin-12/NgCAM2 tetramer, in which homophilic NgCAM binding across the extracellular space occurs simultaneously with a cis-heterophilic interaction of axonin-1 and NgCAM. The enhanced neurite fasciculation after overexpression of NgCAM by adenoviral vectors indicates that NgCAM is the limiting component for the formation of the axonin-12/NgCAM2 complexes and, thus, neurite fasciculation in DRG neurons.

Show MeSH
Related in: MedlinePlus