Identification of a Neural Cell Specific Variant of Microtubule-Associated Protein 4 (original) (raw)
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Identification of a novel microtubule-binding domain in microtubule-associated protein 1A (MAP1A)
1994
Several microtubule-associated proteins (MAPs) have been shown to bind to microtubules via short sequences with repeated amino acids motifs. A microtubule-binding domain has hitherto not been defined for the adult brain microtubule-associated protein 1A (MAP1A). We have searched for a microtubule-binding domain by expressing different protein regions of MAP1A in cultured cell lines using cDNA constructs. One construct included an area with homology to the microtubule-binding domain of MAP1B (Noble et al. (1989) J. Cell Biol. 109, 437-448), but this did not bind to microtubules in transfected cells. Further investigation of other areas of MAP1A revealed a protein domain, capable of autonomously binding to microtubules, which bears no homology to any previously described microtubule-binding sequence. This MAP1A domain is rich in charged amino acids, as are other mammalian microtubule-binding domains, but unlike them has no identifiable sequence repeats. Whereas all previously describe...
MAP2a, an Alternatively Spliced Variant of Microtubule-Associated Protein 2
Journal of Neurochemistry, 2002
MAP2, a dendritically localized microtubuleassociated protein (MAP), consists of a pair of high molecular mass (280 kDa) polypeptides, MAP2a and MAP2b, and several low molecular mass (70 kDa) proteins called MAP2c. Although MAP2b and MAP2c have been shown to arise via alternative splicing, it was not clear whether MAP2a is also created by alternative splicing or by posttranslational modification. Using epitope peptide mapping, we have demonstrated that an element specific to MAP2a is situated at its N-terminal end. A cDNA clone from an adult rat brain library was found to contain an additional 246 nucleotides situated at the 5' end of the 9-kb MAP2 mRNA. Antibodies generated against the encoded protein sequence recognize specifically MAP2a in rat brain homogenates. Moreover, although MAP2a, like MAP2b, is found in dendrites and cell bodies, its temporal appearance and cell type-specific distribution in rat brain differs from MAP2b. Key Words: Rat brain -Cytoskeleton -Microtubule -Dendrites -Alternative splicing -Microtubule-associated protein 2.
Characterization of a new 120 kDa microtubule-associated protein (MAP) of rat brain
Neuroscience Letters, 1991
A novel protein was identified in rat brain microtubules using a monoclonal antibody. The immunoreactive protein is a microtubule-associated protein (MAP) by the criteria of co-purification with tubulin through repeated cycles of microtubule polymerisation in vitro. It belongs to the class of thermostable MAPs and runs as a closely spaced polypeptide doublet of 120 kDa on SDS PAGE gels. MAP-120 kDa is brain-and neuron-specific and is localized predominantly in Purkinje cell bodies and dendrites in the cerebellum and in dendritic compartments of pyramidal and granule neurons in the hippocampus and dentate gyrus. During postnatal brain development, MAP-120 kD levels increase about 3 to 4-fold.
Heterogeneity of microtubule-associated protein (MAP2) in vertebrate brains
Brain Research, 1987
We have utilized monoclonal anti ies to investigate the antigenic diversity of MAIT-immunoreactive proteins in the nervous system of vertebrates. We found that domains defined by the monocional antibodies differed in their conservation across vertebrate evolution, ranging from wide cross-reactivity with almost all vertebrates (mammals, birds, reptiles and amphibians) to a very limited cross-reactivity with only few mammalian *es. Wowever. we did not find MAP?-immunoreactive proteins in fish species with either of the monoclonal or polyclonal anti. There was also a significant divergence in the apparent molecular weight of MAPZ, even in closely related species. For example. rent species of wild mice and strains of laboratory mice showed variations of up to 30 kDa in their apparent molecular mass. Using alkaline phospkata. under conditions that dephosphorylate neurofilaments. we showed that the observed heterogeneity was not the result of variations in the phosphate content. The heterogeneity in molecular weight of MAP2 may, therefore, be the result of changes in primary structure, transcriptional variations or different post-translational modifications. The heterogeneity of MAP2, as well as its specific distribution and implicated interactions with other molecules. underscore the complexity of MAP2 andtential for structural and function rsity. The phylogenic analysis of such a complex molecule also provides a method to est the uniqueness of monoclonal an ies and the degree of their conservation for their corresponding epitopes. 19.23.39.44 AP2 can be cleaved into two structural domains: a fragment which binds the microtubules and promotes tubulin assembly':'and the arm projecting from the microtubule surface which contains a binding site for the regulatory subunit of CA
We previously reported that the microtubule-stabilizing activity of a microtubule-associated protein (MAP) 4 variant, with a deletion in the Pro-rich region (MAP4-SP), was lower than that of a variant with a full length Pro-rich region (MAP4-LP). However, it remained unclear whether the deletion of the specific site in the Pro-rich region is responsible for the reduction of the microtubule-stabilizing activity. To answer this question, we examined the microtubule-stabilizing activities of four different MAP4 variants, MAP4-SP, MAP4-LP, and two additional MAP4-LP variants lacking a part of the Repeat region, and considered the correlation between the activity and the structure. When microtubules assembled in the presence of each of the MAP4 variants were treated with nocodazole for disassembly, the MAP4-SP-induced microtubules were significantly less stable than the other variant-induced microtubules. Another set of experiments, in which the microtubules were allowed to disassemble b...
FEBS Letters, 1997
In order to study the function of the bovine MAP4 microtubule-binding domain (the assembly-promoting (AP) sequence region), a fragment corresponding to the AP sequence region was prepared using an Escherichia coli expression system. When the fragment was mixed with purified tubulin at 37°C, the fragment caused a time-and dose-dependent turbidity increase, and the fragment bound to tubulin. However, the products were cold-stable, and amorphous aggregates were observed by electron microscopy. Using axonemes as the seeds for microtubule assembly, the microtubule-elongating activity of the fragment was examined. A dose-dependent turbidity increase of the sample was observed, and electron microscopic observation revealed that microtubules were dose-dependently elongated from the axonemes. Consequently, the AP sequence region does not nucleate microtubules, but elongates them.
Journal of Biological Chemistry, 2004
The related high molecular mass microtubuleassociated proteins (MAPs) MAP1A and MAP1B are predominantly expressed in the nervous system and are involved in axon guidance and synaptic function. MAP1B is implicated in fragile X mental retardation, giant axonal neuropathy, and ataxia type 1. We report the functional characterization of a novel member of the microtubule-associated protein 1 family, which we termed MAP1S (corresponding to sequence data bank entries for VCY2IP1 and C19ORF5). MAP1S contains the three hallmark domains of the microtubuleassociated protein 1 family but hardly any additional sequences. It decorates neuronal microtubules and copurifies with tubulin from brain. MAP1S is synthesized as a precursor protein that is partially cleaved into heavy and light chains in a tissue-specific manner. Heavy and light chains interact to form the MAP1S complex. The light chain binds, bundles, and stabilizes microtubules and binds to actin. The heavy chain appears to regulate light chain activity. In contrast to MAP1A and MAP1B, MAP1S is expressed in a wide range of tissues in addition to neurons and represents the non-neuronal counterpart of this cytolinker family.