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A Matus

Publications and source records attributed to A Matus.

At least 91 records · Page 5Linked to original sources
PubMed1985

MAP3: characterization of a novel microtubule-associated protein.

Using monoclonal antibodies we have characterized a brain protein that copurifies with microtubules. We identify it as a microtubule-associated protein (MAP) by the following criteria: it copolymerizes with tubulin through repeated cycles of microtubule assembly in vitro; it is not associated with any brain subcellular fraction other than microtubules; in double-label immunofluorescence experiments antibodies against this protein stain the same fibrous elements in cultured cells as are stained by antitubulin; and this fibrous staining pattern is dispersed when cytoplasmic microtubules are disrupted by colchicine. Because it is distinct from previously described MAPs we designate this novel species MAP3. The MAP3 protein consists of a closely spaced pair of polypeptides on SDS gels, Mr 180,000, which are present in both glial (glioma C6) and neuronal (neuroblastoma B104) cell lines. In brain the MAP3 antigen is present in both neurons and glia. In nerve cells its distribution is strikingly restricted: anti-MAP3 staining is detectable only in neurofilament-rich axons. It is not, however, a component of isolated brain intermediate filaments.

Animals↗
PubMed1985

Differences in the developmental patterns of three microtubule-associated proteins in the rat cerebellum.

The developmental distribution patterns of microtubule-associated proteins (MAPs) 1, 2, and 3 were studied using three monoclonal antibodies. Immunochemical staining at the light and electron microscopic levels demonstrated the specific localization of each MAP in different cellular and subcellular compartments. MAP2, which is specifically associated with dendritic microtubules in the adult brain, is strictly associated with growing dendrites from the onset of their formation. MAP3, a recently described MAP of Mr = 180,000, which in the adult brain is associated with neurofilament-rich axons and glial processes, is associated with axons from the beginning of outgrowth. Although MAP3 is not detectable in granule cells and their parallel fiber axons in the mature cerebellum, it does appear transitorily in these axons during development. During neuronal differentiation, MAP1 is found first in axons and only later in dendrites where the highest concentrations are eventually to be found. These results indicate that the combined appearance of MAP1 and MAP2 (dendrites) or MAP1 and MAP3 (axons) correlates with the appearance of morphologically distinct microtubules and provide further evidence that specific MAPs are molecular determinants of dendritic and axonal formation.

Animals↗
PubMed1984

Light and electron microscopic studies of the distribution of microtubule-associated protein 2 in rat brain: a difference between dendritic and axonal cytoskeletons.

A specific antiserum was used to ascertain the distribution of microtubule-associated protein 2 (MAP2) in the rat brain at the light and electron microscope levels. Light microscopy showed MAP2 to be present only in neurons, and only in the dendrites and the perikaryon of each cell. This same polarized distribution pattern was found in the Purkinje, Golgi, basket, stellate, and granule cells of the cerebellum, and also in neurons of the hippocampus, the olfactory bulb, and the midbrain. While labelling of the dendritic arborization was extensive and intense, MAP2 density tended to decrease in the proximal dendritic trunk. Particularly in large neurons (e.g., Purkinje, Golgi, and pyramidal cells), staining was reproducibly weaker in the cell body than in the main dendrites. Dendritic contours generally appeared smooth, without any evidence of staining of dendritic spines. An electron microscope examination of the cerebellum confirmed the presence of MAP2 reactivity in neurons and its absence from axons and non-neuronal cells. MAP2 in dendrites was associated with microtubules, while MAP2 in neuronal perikarya was associated with polyribosomes. There was no evidence of specific staining in dendritic spines and in postsynaptic densities. MAP2 is a novel dendritic marker and labels part of a specific dendritic cytoskeleton, different from that in axons and non-neuronal cells.

Animals↗
PubMed1984

Sodium ions regulate a specific population of acidic amino acid receptors in synaptic membranes.

The regulatory effects of Na+ on C1-/Ca2+-dependent and C1-/Ca2+-independent L-glutamate binding sites were examined. In Tris-C1-/Ca2+ buffer, the binding of L-[3H]-glutamate to rat brain synaptic membranes was 5-fold higher than in Tris-acetate buffer. Low concentrations of Na+ (less than 5 mM) markedly depressed L-glutamate binding when assayed in Tris-C1/Ca2+ buffer, and this effect was attenuated by the selective blocker of C1-/Ca2+-dependent binding sites, DL-2-amino-4-phosphonobutyrate (APB). Scatchard analyses indicated that the effect of Na+ was due to a decrease in the number of C1-/Ca2+-dependent binding sites with no change in affinity. In Tris-acetate buffer, low concentrations of Na+ had little effect on L-glutamate binding. Dose-response curves for the inhibition of L-glutamate binding by DL-APB indicated a predominant high-affinity (Ki 5-10 microM) inhibitory component in Tris-C1-/Ca2+ buffer, but mainly a low-affinity component (Ki 1-2 mM) in Tris-acetate buffer and in Tris-C1-/Ca2+ buffer containing Na+. These data indicate that low concentrations of Na+ regulate specifically the C1-/Ca2+-dependent, APB-sensitive class of L-glutamate binding sites.

Aminobutyrates↗
PubMed1984

Selective association of N-methyl aspartate and quisqualate types of L-glutamate receptor with brain postsynaptic densities.

Recognition sites for the excitatory neurotransmitter, L-glutamate, were studied in synaptic plasma membranes and postsynaptic densities (PSDs) isolated from rat brains. The results demonstrate (i) that L-glutamate binding sites may be resolved into three distinct subtypes (categories A1, A2, and A4), each corresponding to an electrophysiologically identified receptor class, and (ii) that the N-methyl aspartate (A1) and quisqualate (A2) receptor types are selectively associated with PSDs. L-[3H]Glutamate bound to an apparently homogeneous population of sites in PSDs with a Kd of 3.39 X 10(-7) M and a Bmax (maximum number of binding sites) of 6.1 pmol/mg of protein. Inhibition studies demonstrated that these sites could be resolved into two distinct subtypes. N-Methyl aspartate maximally inhibited 58% of PSD-located L-glutamate binding sites with a Ki of 7.2 X 10(-6) M (the A1 site), and quisqualate inhibited 42% with a Ki of 1.1 X 10(-6) M (the A2 site); the effects of both substances were additive. Experiments with a range of acidic amino acid analogues indicated that the ligand selectivities of these two binding sites conformed to those of the N-methyl D-aspartate and quisqualate receptor classes defined electrophysiologically. The Cl--dependent population of L-glutamate binding sites (the A4 site), which predominates in synaptic membranes, was absent from isolated PSDs.

Amino Acids↗
PubMed1984

Surface antigens of brain synapses: identification of minor proteins using polyclonal antisera.

Antigenic proteins of brain synaptic plasma membranes (SPM) and postsynaptic densities (PSD) were characterized using antisera raised against SPM. Immunostaining of brain sections showed that the antigens were restricted to synapses, and electron microscopy revealed staining at both presynaptic terminals and PSDs. In primary brain cell cultures the antisera were also neuron-specific but the antigens were distributed throughout the entire neuronal plasma membrane, suggesting that some restrictive influence present in whole tissue is absent when neurons are grown dispersed. The antigenic proteins with which these antisera react were identified using SDS gel immunoblots. SPM and PSD differed from one another in their characteristic antigenic proteins. Comparison with amido-black stained gel blots showed that in both cases most of these did not correspond to known abundant proteins of SPM or PSDs revealed by conventional biochemical techniques. None of the antigens revealed by the polyclonal antisera were detected by any of a large series of monoclonal antibodies against SPM.

Animals↗
PubMed1984

Immunocytochemical localization of microtubule-associated protein 1 in rat cerebellum using monoclonal antibodies.

Immunohistochemical staining with monoclonal antibodies showed that microtubule-associated protein 1 (MAP1) has a restricted cellular distribution in the rat cerebellum. Anti-MAP1 staining was found only in neurons, where it was much stronger in dendrites than in axons. There were striking variations in the apparent concentration of MAP1 in different classes of neurons. Purkinje cells were the most strongly labeled, while granule cell neurons gave a faint, threshold-level reaction with the antibody. The reaction of Golgi neurons was intermediate between these two extremes. Equivalent results were obtained using two different methods of tissue preparation. Thus MAP1 appears to be a neuron-specific protein that is highly concentrated in dendrites and occurs at markedly different levels in different types of neurons. These observations provide further indications of heterogeneity among brain microtubules.

Animals↗
PubMed1984

18B1: an axon-specific antigen associated with many proteins.

We describe an antigen, 18B1, defined by a monoclonal antibody. Immunoperoxidase staining of brain sections shows that 18B1 is selectively associated with neurofilament-rich axons. Antibody staining of sodium dodecyl sulphate-gel blots, on the other hand, shows that 18B1 is associated with a large number of proteins, none of which are structural components of brain neurofilaments. The antigen is sensitive to a variety of proteases but is not degraded by various glycosidases, suggesting that 18B1 is probably an amino acid sequence. Its association with neurofilament-rich axons together with its absence from neurofilaments themselves suggests that it may be involved in mediating interactions between neurofilaments and the proteins that bear it.

Animals↗
PubMed1984

L-glutamate receptor heterogeneity: labeling of distinct receptor sub-types using radioligand binding techniques.

This study demonstrates (1) that L-[3H]glutamate labels 3 distinct binding sites (types A1, A2 and A4) in isolated rat brain membranes and (2) that only the N-methyl-aspartate (A1) and quisqualate (A2) receptor classes are associated with the postsynaptic density (PSD). L-[3H]glutamate bound to PSDs with Kd 339 nM and Bmax 6 X 1 pmol/mg protein. These sites were resolved into 2 distinct sub-types on the basis of inhibition studies. N-Methyl-aspartate maximally inhibited 57% of PSD-located L-glutamate binding sites (the A1 site) and quisqualate 43% (the A2 site); the effects of both substances were additive. The ligand selectivities of these 2 sites indicated their identity with the N-methyl-D-aspartate and quisqualate receptor classes defined electrophysiologically. The C1--dependent population of L-glutamate binding sites (the A4 site) which predominates in synaptic membranes was absent from PSDs.

Animals↗
PubMed1984

Differences in the cellular distributions of two microtubule-associated proteins, MAP1 and MAP2, in rat brain.

The distribution of microtubule-associated proteins (MAPs) 1 and 2 in rat brain was studied using monoclonal antibodies. Immunochemical staining showed that both MAP1 and MAP2 are present only in neurons and both are highly concentrated in dendrites compared to axons. Otherwise, they differed in distribution in various ways. MAP1 was present at low levels in axons, whereas MAP2 was never detectable in axons with either of two different fixation methods used. In the cerebellum the two MAPs differed in relative concentration in various classes on neurons. Thus, anti-MAP1 staining was strong in Purkinje cells but very faint in granule cells, whereas anti-MAP2 staining was strong in both. There were also distributional differences within the same cell. Thus, in Purkinje cells, anti-MAP1 staining is strong in the cell body, initial axon segment and throughout the dendritic tree, but anti-MAP2 staining is present only in dendrites beyond the initial proximal portion. These results suggest that microtubules with different molecular compositions are present in the cerebellum where they are distributed differently between cells as well as within the same cell.

Animals↗
PubMed1982

MIT-23: a mitochondrial marker for terminal neuronal differentiation defined by a monoclonal antibody.

We describe a monoclonal antibody directed against a neuron-specific mitochondrial protein from rat brain. On protein blots the antibody recognizes a single polypeptide of apparent molecular weight of 23,000. By solid-phase immunoassay the antigen was detected in nonneural tissues. Within neurons, the antibody stains cytoplasmic granules that immunoelectron microscopy shows are mitochondria, hence the designation MIT-23. Immunocytochemical staining of the cerebellar cortex showed that MIT-23 occurs in all the neuronal types but is absent from glial and other nonneuronal cells. During neonatal development of the cerebellum, MIT-23 appears in neurons after their final cell division or migration is completed, suggesting that specific proteins associated with mitochondria participate in neuronal maturation.

Animals↗
PubMed1982

High actin concentrations in brain dendritic spines and postsynaptic densities.

Antibodies against actin were used to corroborate the presence of actin as a major component protein of isolated brain postsynaptic densities. The same antibodies also were used as an immunohistochemical stain to study the distribution of actin in sections of intact brain tissue. This showed two major sites where actin is concentrated: smooth muscle cells around blood vessels and postsynaptic sites. In the postsynaptic area the highest concentration of actin occurs in postsynaptic densities and there also is intense staining in the surrounding cytoplasm, especially within dendritic spines. Antiactin staining was much weaker in other parts of neurons and in glial cells. The high concentration of actin in dendritic spines may be related to shape changes that these structures have been found to undergo in response to prolonged afferent stimulation.

Actins↗
PubMed1982

Monoclonal antibodies identify novel neural antigens.

Monoclonal antibodies (Mabs) were raised against synaptic plasma membranes from rat cerebellum. The hybridomas were screened with a solid-phase immunoassay, the positive lines were characterized by their immunoperoxidase staining pattern on cerebellum, and the specific polypeptide antigens were identified on protein blots. Among the Mabs described are some that stain only neurons or only glia and others that react with specific parts of cells, such as axons, dendrites, and synapses. Many Mabs reveal novel relationships between antigens and the cells in which they occur. For example, a Mab designated 7D5 reacts with a family of greater than 30 proteins but stains only glial cells. Several Mabs stain punctate sites of synaptic size and distribution in the cerebellar cortex but each reacts with a different subset of polypeptides. One of the most restricted cytological staining patterns is given by 12D5, which stains punctate sites in the granular layer of the cerebellar cortex and reacts with a single polypeptide band of apparent Mr 270,000. These results illustrate the feasibility of raising Mabs that can be used to follow the expression of specific gene products during brain development.

Animals↗
PubMed1982

Initial phase of dendrite growth: evidence for the involvement of high molecular weight microtubule-associated proteins (HMWP) before the appearance of tubulin.

It has recently been shown that high molecular weight microtubule-associated proteins (HMWP) in the brain are present in dendrites and are absent from axons (Matus et al., 1981, Proc. Natl. Acad. Sci. U. S. A. 78:3010-3014). In this study we followed the appearance of both HMWP and tubulin in the neonatal rat cerebellum by immunoperoxidase staining, concentrating particularly on comparing Purkinje cell dendrites with adjacent granule cell axons. In the axons both immunohistochemically demonstrable tubulin and structurally distinct microtubules are present at all stages of development. By contrast the Purkinje cell dendrites contain better neither tubulin nor microtubules at early stages of their growth. However, immunoperoxidase staining showed that these developing dendrites are rich in HMWP which are particularly concentrated in the dendritic distal regions. HMWP are also present as patches beneath the surface membrane of the cell body before the emergence of dendrites. Based on this data and the well-documented ability of HMWP to promote microtubule assembly, we propose the hypothesis that during the initial phase of Purkinje neuron differentiation HMWP form part of a specialized cytoskeletal structure which acts as a specifier for the development of dendrites as opposed to axons.

Axons↗
PubMed1981

gamma-Aminobutyric acid receptors in brain postsynaptic densities.

Rat brain synaptic plasma membranes contain two receptorlike binding sites for the inhibitory transmitter gamma-aminobutyric acid. Postsynaptic junctional structures (postsynaptic densities) isolated from these membranes contain only the higher affinity site enriched more than sixfold compared to the membranes. The results provide the first direct evidence for the association of transmitter receptors with postsynaptic junctional sites in the brain.

Animals↗