Microtubule-associated proteins bind specifically to the 70-kDa neurofilament protein (original) (raw)
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The Journal of Cell Biology, 1982
Mammalian neurofilaments prepared from brain and spinal cord by either of two methods partially inhibit the in vitro assembly of microtubules. This inhibition is shown to be due to the association of a complex of high molecular weight microtubule-associated proteins (MAP1 and MAP2) and tubulin with the neurofilament. Further analysis of the association reveals a saturable binding of purified brain MAPs to purified neurofilaments with a Kd of 10(-7) M. Purified astroglial filaments neither inhibit microtubule assembly nor show significant binding of MAPs. It is proposed that the MAPs might function as one element in a network of intraorganellar links in the cytoplasm.
Neurofilaments Bind Tubulin and Modulate Its Polymerization
The Journal of Neuroscience, 2009
Neurofilaments assemble from three intermediate-filament proteins, contribute to the radial growth of axons, and are exceptionally stable. Microtubules are dynamic structures that assemble from tubulin dimers to support intracellular transport of molecules and organelles. We show here that neurofilaments, and other intermediate-filament proteins, contain motifs in their N-terminal domains that bind unassembled tubulin. Peptides containing such motifs inhibit thein vitropolymerization of microtubules and can be taken up by cultured cells in which they disrupt microtubules leading to altered cell shapes and an arrest of division. In transgenic mice in which neurofilaments are withheld from the axonal compartment, axonal tubulin accumulation is normal but microtubules assemble in excessive numbers. These observations suggest a model in which axonal neurofilaments modulate local microtubule assembly. This capacity also suggests novel mechanisms through which inherited or acquired disrup...
Journal of Cell Science, 2009
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 w...
The Journal of biological chemistry, 1986
Two major brain microtubule-associated proteins (MAPs), MAP2 and tau, were found to bind to the intermediate filaments reassembled from neurofilament 70-kDa subunit protein (= 70-kDa filaments). The binding was saturable. The apparent dissociation constant (KD) for the binding of MAP2 to the 70-kDa filaments was estimated to be 4.8 X 10(-7) M, and the maximum binding reached 1 mol of MAP2/approximately 30 mol of 70-kDa protein. The apparent KD for the tau binding was 1.6 X 10(-6) M, and the maximum binding was 1 mol of tau/approximately 3 mol of 70-kDa protein. It was also found that MAP2 and tau did not compete with each other for binding to the 70-kDa filaments. Most interestingly, calmodulin, a ubiquitous Ca2+-binding protein in eukaryotic cells, was found to inhibit the binding of MAP2 and tau to the 70-kDa filaments. The inhibition by calmodulin was regulated by changes in Ca2+ concentration around 10(-6) M, and was canceled by trifluoperazine, a calmodulin inhibitor.
Anti-200 kDa neurofilament antibody cross-reacts with microtubule-associated protein-2 (MAP-2)
Journal of Neuroscience Research, 1989
An antibody prepared against purified 200-kDa neurofilament (NF) subunit was found to cross-react with a high molecular weight polypeptide present in rat brain cytoskeletal extracts starting from early postnatal development. This polypeptide was found to be highly concentrated in microtubule preparations and was specifically recognized as the 280-kDa microtubule-associated protein3 (MAP-2). Our results, besides suggesting the existence of common epitopes between the heavy NF subunit and MAP-2, suggest the possibility of an interaction between two of the most important neuronal cytoskeletal organelles: NFs and microtubules.
Ultrastructural evidence that insoluble microtubules are components of the neurofibrillary tangle
European Archives of Psychiatry and Neurological Sciences, 1990
The ultrastructure of Alzheimer's neurofibrillary tangles is heterogeneous and includes abnormal paired helical filaments (PHF) and various other insoluble structures. Insoluble non-PHF components isolated from neurofibrillary tangles were examined by electron microscopy. Comparison of these fractions with normal assembled neurofilaments and normal brain microtubules revealed scattered profiles which were morphologically (not chemically) identical to structures present in the microtubule, but not in the neurofilament preparations. These results support the notion that insoluble microtubules contribute to the make up of the neurofibrillary tangle. Based on these findings, preliminary experiments were conducted which suggest that non-enzymatic glycosylation may be a pathway leading to insolubility of the microtubules.
Study of the 10-nm-filament fraction isolated during the standard microtubule preparation
The Biochemical journal, 1980
The cold non-depolymerizable fractions obtained during the standard procedure for the isolation of microtubules from ox brain stem-cerebral hemispheres and spinal cord have been studied. The cerebral-hemisphere preparation was composed of 10-nm filaments but also contained large amounts of membranes. The polypeptide content included tubulin, microtubule-associated proteins and minor proteins corresponding to the neurofilament triplet of proteins of mol.wt. 210 000, 160 000 and 70 000 respectively. The brain-stem preparation contained more 10-nm filaments than membranes. The polypeptide content consisted of the neurofilament triplet (35%), tubulin (30%) and minor proteins. In contrast, the spinal-cord preparation was mainly composed of 10-nm filaments, free of membranes and containing essentially the neurofilament protein triplet (64%). These filaments appeared very similar to the peripheral-nervous-system neurofilaments described by several authors. Since the best neurofilament from...