Limits...
[Beta]IV-spectrin regulates sodium channel clustering through ankyrin-G at axon initial segments and nodes of Ranvier.

Komada M, Soriano P - J. Cell Biol. (2002)

Bottom Line: In betaIV-spectrin- neurons, neither ankyrin-G nor voltage-gated sodium channels (VGSC) are correctly clustered at these sites, suggesting that impaired action potential caused by mislocalization of VGSC leads to the phenotype.Conversely, in ankyrin-G- neurons, betaIV-spectrin is not localized to these sites.These results indicate that betaIV-spectrin and ankyrin-G mutually stabilize the membrane protein cluster and the linked membrane cytoskeleton at AIS and NR.

View Article: PubMed Central - PubMed

Affiliation: Program in Developmental Biology and Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA. makomada@bio.titech.ac.jp

ABSTRACT
beta-Spectrin and ankyrin are major components of the membrane cytoskeleton. We have generated mice carrying a mutation in the betaIV-spectrin gene using gene trapping in embryonic stem cells. Mice homozygous for the mutation exhibit tremors and contraction of hindlimbs. betaIV-spectrin expression is mostly restricted to neurons, where it colocalizes with and binds to ankyrin-G at axon initial segments (AISs) and nodes of Ranvier (NR). In betaIV-spectrin- neurons, neither ankyrin-G nor voltage-gated sodium channels (VGSC) are correctly clustered at these sites, suggesting that impaired action potential caused by mislocalization of VGSC leads to the phenotype. Conversely, in ankyrin-G- neurons, betaIV-spectrin is not localized to these sites. These results indicate that betaIV-spectrin and ankyrin-G mutually stabilize the membrane protein cluster and the linked membrane cytoskeleton at AIS and NR.

Show MeSH

Related in: MedlinePlus

Clustering of VGSC at AIS of βIV-spectrin– cerebral, hippocampal, and cerebellar neurons. Cerebral cortex (A, A′, B, and B′), hippocampus (C, C′, D, and D′), and cerebellum (E, E′, F, and F′) of wild-type (A, A′, C, C′, E, and E′) and βIV-spectrin– (B, B′, D, D′, F, and F′) mice were stained with anti–βIV-spectrin (A, B, C, D, E, and F) together with anti–pan-sodium channel (pan-SC; A′, B′, C′, and D′) or anti-Nav1.6 (E′ and F′). Arrowheads indicate AIS of cerebral (A, A′, and B′), hippocampal pyramidal (C and C′), and Purkinje (E and E') neurons. The granular layer (G), Purkinje cell layer (P), and molecular layer (M) of the cerebellum are separated by dotted lines (E, E′, F, and F′). Mice were killed at 3 mo of age. Bars, 20 μm.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2199236&req=5

fig6: Clustering of VGSC at AIS of βIV-spectrin– cerebral, hippocampal, and cerebellar neurons. Cerebral cortex (A, A′, B, and B′), hippocampus (C, C′, D, and D′), and cerebellum (E, E′, F, and F′) of wild-type (A, A′, C, C′, E, and E′) and βIV-spectrin– (B, B′, D, D′, F, and F′) mice were stained with anti–βIV-spectrin (A, B, C, D, E, and F) together with anti–pan-sodium channel (pan-SC; A′, B′, C′, and D′) or anti-Nav1.6 (E′ and F′). Arrowheads indicate AIS of cerebral (A, A′, and B′), hippocampal pyramidal (C and C′), and Purkinje (E and E') neurons. The granular layer (G), Purkinje cell layer (P), and molecular layer (M) of the cerebellum are separated by dotted lines (E, E′, F, and F′). Mice were killed at 3 mo of age. Bars, 20 μm.

Mentions: The localization of VGSC was examined using an anti–pan-sodium channel antibody that recognizes all the known vertebrate sodium channel isoforms (Rasband et al., 1999). In wild-type mice, VGSC colocalized with βIV-spectrin at AIS of cerebral cortex (Fig. 6, A and A′) and hippocampal pyramidal (Fig. 6, C and C′) neurons. However, in βIV-spectrin mutant mice, VGSC staining was very faint in the cerebral cortex (Fig. 6, B and B′) and mostly undetectable in the hippocampus (Fig. 6, D and D′). Similar mislocalization was also observed for a specific sodium channel isoform Nav1.6 (Fig. 6, F and F′), which normally localizes to AIS in Purkinje cells (Fig. 6, E and E′; S. Jenkins and V. Bennett, personal communication).


[Beta]IV-spectrin regulates sodium channel clustering through ankyrin-G at axon initial segments and nodes of Ranvier.

Komada M, Soriano P - J. Cell Biol. (2002)

Clustering of VGSC at AIS of βIV-spectrin– cerebral, hippocampal, and cerebellar neurons. Cerebral cortex (A, A′, B, and B′), hippocampus (C, C′, D, and D′), and cerebellum (E, E′, F, and F′) of wild-type (A, A′, C, C′, E, and E′) and βIV-spectrin– (B, B′, D, D′, F, and F′) mice were stained with anti–βIV-spectrin (A, B, C, D, E, and F) together with anti–pan-sodium channel (pan-SC; A′, B′, C′, and D′) or anti-Nav1.6 (E′ and F′). Arrowheads indicate AIS of cerebral (A, A′, and B′), hippocampal pyramidal (C and C′), and Purkinje (E and E') neurons. The granular layer (G), Purkinje cell layer (P), and molecular layer (M) of the cerebellum are separated by dotted lines (E, E′, F, and F′). Mice were killed at 3 mo of age. Bars, 20 μm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2199236&req=5

fig6: Clustering of VGSC at AIS of βIV-spectrin– cerebral, hippocampal, and cerebellar neurons. Cerebral cortex (A, A′, B, and B′), hippocampus (C, C′, D, and D′), and cerebellum (E, E′, F, and F′) of wild-type (A, A′, C, C′, E, and E′) and βIV-spectrin– (B, B′, D, D′, F, and F′) mice were stained with anti–βIV-spectrin (A, B, C, D, E, and F) together with anti–pan-sodium channel (pan-SC; A′, B′, C′, and D′) or anti-Nav1.6 (E′ and F′). Arrowheads indicate AIS of cerebral (A, A′, and B′), hippocampal pyramidal (C and C′), and Purkinje (E and E') neurons. The granular layer (G), Purkinje cell layer (P), and molecular layer (M) of the cerebellum are separated by dotted lines (E, E′, F, and F′). Mice were killed at 3 mo of age. Bars, 20 μm.
Mentions: The localization of VGSC was examined using an anti–pan-sodium channel antibody that recognizes all the known vertebrate sodium channel isoforms (Rasband et al., 1999). In wild-type mice, VGSC colocalized with βIV-spectrin at AIS of cerebral cortex (Fig. 6, A and A′) and hippocampal pyramidal (Fig. 6, C and C′) neurons. However, in βIV-spectrin mutant mice, VGSC staining was very faint in the cerebral cortex (Fig. 6, B and B′) and mostly undetectable in the hippocampus (Fig. 6, D and D′). Similar mislocalization was also observed for a specific sodium channel isoform Nav1.6 (Fig. 6, F and F′), which normally localizes to AIS in Purkinje cells (Fig. 6, E and E′; S. Jenkins and V. Bennett, personal communication).

Bottom Line: In betaIV-spectrin- neurons, neither ankyrin-G nor voltage-gated sodium channels (VGSC) are correctly clustered at these sites, suggesting that impaired action potential caused by mislocalization of VGSC leads to the phenotype.Conversely, in ankyrin-G- neurons, betaIV-spectrin is not localized to these sites.These results indicate that betaIV-spectrin and ankyrin-G mutually stabilize the membrane protein cluster and the linked membrane cytoskeleton at AIS and NR.

View Article: PubMed Central - PubMed

Affiliation: Program in Developmental Biology and Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA. makomada@bio.titech.ac.jp

ABSTRACT
beta-Spectrin and ankyrin are major components of the membrane cytoskeleton. We have generated mice carrying a mutation in the betaIV-spectrin gene using gene trapping in embryonic stem cells. Mice homozygous for the mutation exhibit tremors and contraction of hindlimbs. betaIV-spectrin expression is mostly restricted to neurons, where it colocalizes with and binds to ankyrin-G at axon initial segments (AISs) and nodes of Ranvier (NR). In betaIV-spectrin- neurons, neither ankyrin-G nor voltage-gated sodium channels (VGSC) are correctly clustered at these sites, suggesting that impaired action potential caused by mislocalization of VGSC leads to the phenotype. Conversely, in ankyrin-G- neurons, betaIV-spectrin is not localized to these sites. These results indicate that betaIV-spectrin and ankyrin-G mutually stabilize the membrane protein cluster and the linked membrane cytoskeleton at AIS and NR.

Show MeSH
Related in: MedlinePlus