Neurofilament cross-bridging competes with kinesin-dependent association of neurofilaments with microtubules.
J Cell Sci
; 122(Pt 19): 3579-86, 2009 Oct 01.
Article
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| MEDLINE
| ID: mdl-19737816
ABSTRACT
The phosphorylation of neurofilaments (NFs) has long been considered to regulate their axonal transport rate and in doing so to provide stability to mature axons. Axons contain a centrally situated ;bundle' of closely opposed phospho-NFs that display a high degree of NF-NF associations and phospho-epitopes, surrounded by less phosphorylated ;individual' NFs that are often associated with kinesin and microtubules (MTs). Bundled NFs transport substantially slower than the surrounding individual NFs and might represent a resident population that stabilizes axons and undergoes replacement by individual NFs. To examine this possibility, fractions enriched in bundled NFs and individual NFs were generated from mice and NB2a/d1 cells by sedimentation of cytoskeletons over a sucrose cushion. More kinesin was recovered within individual versus bundled NF fractions. Individual but not bundled NFs aligned with purified MTs under cell-free conditions. The percentage of NFs that aligned with MTs was increased by the addition of kinesin, and inhibited by anti-kinesin antibodies. Bundles dissociated following incubation with EGTA or alkaline phosphatase, generating individual NFs that retained or were depleted of phospho-epitopes, respectively. These dissociated NFs aligned with MTs at a level identical to those originally isolated as individual NFs regardless of phosphorylation state. EGTA-mediated dissociation of bundles was prevented and reversed by excess Ca(2+), whereas individual NFs did not associate in the presence of excess Ca(2+). These findings confirm that bundling competes with NF-MT association, and provide a mechanism by which C-terminal NF phosphorylation might indirectly contribute to the observed slowing in axonal transport of phospho-NFs.
Texto completo:
1
Bases de datos:
MEDLINE
Asunto principal:
Proteínas de Neurofilamentos
/
Cinesinas
/
Microtúbulos
Tipo de estudio:
Risk_factors_studies
Límite:
Animals
Idioma:
En
Revista:
J Cell Sci
Año:
2009
Tipo del documento:
Article
País de afiliación:
Estados Unidos