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Association of TAG-1 with Caspr2 is essential for the molecular organization of juxtaparanodal regions of myelinated fibers.

Traka M, Goutebroze L, Denisenko N, Bessa M, Nifli A, Havaki S, Iwakura Y, Fukamauchi F, Watanabe K, Soliven B, Girault JA, Karagogeos D - J. Cell Biol. (2003)

Bottom Line: Myelination results in a highly segregated distribution of axonal membrane proteins at nodes of Ranvier.In the absence of TAG-1, axonal Caspr2 did not accumulate at juxtaparanodes, and the normal enrichment of shaker-type K+ channels in these regions was severely disrupted, in the central and peripheral nervous systems.This complex is analogous to that described previously at paranodes, suggesting that similar molecules are crucial for different types of axo-glial interactions.

View Article: PubMed Central - PubMed

Affiliation: Department of Basic Science, University of Crete Medical School, Heraklion 71110, Crete, Greece.

ABSTRACT
Myelination results in a highly segregated distribution of axonal membrane proteins at nodes of Ranvier. Here, we show the role in this process of TAG-1, a glycosyl-phosphatidyl-inositol-anchored cell adhesion molecule. In the absence of TAG-1, axonal Caspr2 did not accumulate at juxtaparanodes, and the normal enrichment of shaker-type K+ channels in these regions was severely disrupted, in the central and peripheral nervous systems. In contrast, the localization of protein 4.1B, an axoplasmic partner of Caspr2, was only moderately altered. TAG-1, which is expressed in both neurons and glia, was able to associate in cis with Caspr2 and in trans with itself. Thus, a tripartite intercellular protein complex, comprised of these two proteins, appears critical for axo-glial contacts at juxtaparanodes. This complex is analogous to that described previously at paranodes, suggesting that similar molecules are crucial for different types of axo-glial interactions.

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Cis and trans interactions between TAG-1 and Caspr2 in COS-7 cells. (A–C) Colocalization of Caspr2 and TAG-1 at the plasma membrane of COS-7 cells. COS-7 cells overexpressing either Caspr2 or TAG-1 alone, or both, were processed for indirect IF and laser confocal microscopy analysis. Caspr2 was uniformly localized at the plasma membrane (A, COS_Caspr2). TAG-1 displayed a membrane localization with a patchy appearance (B, COS_TAG-1). In cotransfected cells, Caspr2 (green) and TAG-1 (red) were largely colocalized (yellow) at the plasma membrane with a distribution similar to that of Caspr2 alone (C, COS_Caspr2/TAG-1). Single confocal sections are shown. (D) Association of TAG-1 in trans with itself but not with Caspr2. COS-7 cells overexpressing either TAG-1 alone (COS_TAG-1, a and b), Caspr2 (COS_Caspr2, c and d) or both (COS_Caspr2/TAG-1, e and f) were incubated with a (a and c–f) TAG-1-Fc chimeric protein or a (b) MUC-18-Fc chimera protein, and processed for indirect IF and laser confocal microscopy analysis. The TAG-1-Fc chimeric protein (green) bound to cells expressing (a) TAG-1 alone or in combination with (e) Caspr2 but not to cells expressing (c) Caspr2 alone. Expression of Caspr2 was verified by (d and f) specific IF (red). Stacked confocal images of eight consecutive sections 1 μm apart. Bar, (A–D) 10 μm.
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fig6: Cis and trans interactions between TAG-1 and Caspr2 in COS-7 cells. (A–C) Colocalization of Caspr2 and TAG-1 at the plasma membrane of COS-7 cells. COS-7 cells overexpressing either Caspr2 or TAG-1 alone, or both, were processed for indirect IF and laser confocal microscopy analysis. Caspr2 was uniformly localized at the plasma membrane (A, COS_Caspr2). TAG-1 displayed a membrane localization with a patchy appearance (B, COS_TAG-1). In cotransfected cells, Caspr2 (green) and TAG-1 (red) were largely colocalized (yellow) at the plasma membrane with a distribution similar to that of Caspr2 alone (C, COS_Caspr2/TAG-1). Single confocal sections are shown. (D) Association of TAG-1 in trans with itself but not with Caspr2. COS-7 cells overexpressing either TAG-1 alone (COS_TAG-1, a and b), Caspr2 (COS_Caspr2, c and d) or both (COS_Caspr2/TAG-1, e and f) were incubated with a (a and c–f) TAG-1-Fc chimeric protein or a (b) MUC-18-Fc chimera protein, and processed for indirect IF and laser confocal microscopy analysis. The TAG-1-Fc chimeric protein (green) bound to cells expressing (a) TAG-1 alone or in combination with (e) Caspr2 but not to cells expressing (c) Caspr2 alone. Expression of Caspr2 was verified by (d and f) specific IF (red). Stacked confocal images of eight consecutive sections 1 μm apart. Bar, (A–D) 10 μm.

Mentions: We investigated whether the association of TAG-1 and Caspr2 altered their subcellular localization in transfected COS-7 cells. When transfected alone, Caspr2 or TAG-1 were, for the most part, localized at the level of the plasma membrane (Fig. 6, A and B). However, the IR pattern of these two proteins was different because Caspr2 appeared rather uniformly distributed, whereas TAG-1-IR had a punctate or patchy appearance, as reported previously in transfected CHO cells (Buttiglione et al., 1998). When both proteins were simultaneously expressed, they were largely colocalized at the plasma membrane, and their distribution appeared similar to that of Caspr2 alone (Fig. 6 C).


Association of TAG-1 with Caspr2 is essential for the molecular organization of juxtaparanodal regions of myelinated fibers.

Traka M, Goutebroze L, Denisenko N, Bessa M, Nifli A, Havaki S, Iwakura Y, Fukamauchi F, Watanabe K, Soliven B, Girault JA, Karagogeos D - J. Cell Biol. (2003)

Cis and trans interactions between TAG-1 and Caspr2 in COS-7 cells. (A–C) Colocalization of Caspr2 and TAG-1 at the plasma membrane of COS-7 cells. COS-7 cells overexpressing either Caspr2 or TAG-1 alone, or both, were processed for indirect IF and laser confocal microscopy analysis. Caspr2 was uniformly localized at the plasma membrane (A, COS_Caspr2). TAG-1 displayed a membrane localization with a patchy appearance (B, COS_TAG-1). In cotransfected cells, Caspr2 (green) and TAG-1 (red) were largely colocalized (yellow) at the plasma membrane with a distribution similar to that of Caspr2 alone (C, COS_Caspr2/TAG-1). Single confocal sections are shown. (D) Association of TAG-1 in trans with itself but not with Caspr2. COS-7 cells overexpressing either TAG-1 alone (COS_TAG-1, a and b), Caspr2 (COS_Caspr2, c and d) or both (COS_Caspr2/TAG-1, e and f) were incubated with a (a and c–f) TAG-1-Fc chimeric protein or a (b) MUC-18-Fc chimera protein, and processed for indirect IF and laser confocal microscopy analysis. The TAG-1-Fc chimeric protein (green) bound to cells expressing (a) TAG-1 alone or in combination with (e) Caspr2 but not to cells expressing (c) Caspr2 alone. Expression of Caspr2 was verified by (d and f) specific IF (red). Stacked confocal images of eight consecutive sections 1 μm apart. Bar, (A–D) 10 μm.
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fig6: Cis and trans interactions between TAG-1 and Caspr2 in COS-7 cells. (A–C) Colocalization of Caspr2 and TAG-1 at the plasma membrane of COS-7 cells. COS-7 cells overexpressing either Caspr2 or TAG-1 alone, or both, were processed for indirect IF and laser confocal microscopy analysis. Caspr2 was uniformly localized at the plasma membrane (A, COS_Caspr2). TAG-1 displayed a membrane localization with a patchy appearance (B, COS_TAG-1). In cotransfected cells, Caspr2 (green) and TAG-1 (red) were largely colocalized (yellow) at the plasma membrane with a distribution similar to that of Caspr2 alone (C, COS_Caspr2/TAG-1). Single confocal sections are shown. (D) Association of TAG-1 in trans with itself but not with Caspr2. COS-7 cells overexpressing either TAG-1 alone (COS_TAG-1, a and b), Caspr2 (COS_Caspr2, c and d) or both (COS_Caspr2/TAG-1, e and f) were incubated with a (a and c–f) TAG-1-Fc chimeric protein or a (b) MUC-18-Fc chimera protein, and processed for indirect IF and laser confocal microscopy analysis. The TAG-1-Fc chimeric protein (green) bound to cells expressing (a) TAG-1 alone or in combination with (e) Caspr2 but not to cells expressing (c) Caspr2 alone. Expression of Caspr2 was verified by (d and f) specific IF (red). Stacked confocal images of eight consecutive sections 1 μm apart. Bar, (A–D) 10 μm.
Mentions: We investigated whether the association of TAG-1 and Caspr2 altered their subcellular localization in transfected COS-7 cells. When transfected alone, Caspr2 or TAG-1 were, for the most part, localized at the level of the plasma membrane (Fig. 6, A and B). However, the IR pattern of these two proteins was different because Caspr2 appeared rather uniformly distributed, whereas TAG-1-IR had a punctate or patchy appearance, as reported previously in transfected CHO cells (Buttiglione et al., 1998). When both proteins were simultaneously expressed, they were largely colocalized at the plasma membrane, and their distribution appeared similar to that of Caspr2 alone (Fig. 6 C).

Bottom Line: Myelination results in a highly segregated distribution of axonal membrane proteins at nodes of Ranvier.In the absence of TAG-1, axonal Caspr2 did not accumulate at juxtaparanodes, and the normal enrichment of shaker-type K+ channels in these regions was severely disrupted, in the central and peripheral nervous systems.This complex is analogous to that described previously at paranodes, suggesting that similar molecules are crucial for different types of axo-glial interactions.

View Article: PubMed Central - PubMed

Affiliation: Department of Basic Science, University of Crete Medical School, Heraklion 71110, Crete, Greece.

ABSTRACT
Myelination results in a highly segregated distribution of axonal membrane proteins at nodes of Ranvier. Here, we show the role in this process of TAG-1, a glycosyl-phosphatidyl-inositol-anchored cell adhesion molecule. In the absence of TAG-1, axonal Caspr2 did not accumulate at juxtaparanodes, and the normal enrichment of shaker-type K+ channels in these regions was severely disrupted, in the central and peripheral nervous systems. In contrast, the localization of protein 4.1B, an axoplasmic partner of Caspr2, was only moderately altered. TAG-1, which is expressed in both neurons and glia, was able to associate in cis with Caspr2 and in trans with itself. Thus, a tripartite intercellular protein complex, comprised of these two proteins, appears critical for axo-glial contacts at juxtaparanodes. This complex is analogous to that described previously at paranodes, suggesting that similar molecules are crucial for different types of axo-glial interactions.

Show MeSH
Related in: MedlinePlus