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I Hermans-Borgmeyer

Publications and source records attributed to I Hermans-Borgmeyer.

49 records · Page 3Linked to original sources
PubMed1991

The nicotinic receptor genes.

The causative factor(s) of Alzheimer's disease (AD) are presently unknown. However, it has been shown that the number as well as the fraction of high- to low-affinity nicotine binding sites is altered in patients suffering from this disease. This finding, along with the identification of seven genes which code for nicotinic receptors expressed in the mammalian brain, has led to the idea that one nicotinic receptor subtype may be specifically altered in AD. The present article reviews how, through a molecular genetic approach, a family of genes coding for nicotinic acetylcholine receptor subtypes was uncovered. Also discussed is the use of in situ hybridization to determine the distribution of expression of the mRNA encoding for each receptor subtype and the patch clamp technique to characterize their biophysical properties. Determination of the promoters of these genes, as well as the properties of the expressed receptor subtypes, may make it possible to design new specific nicotinic receptor subtype drugs that will treat not only the symptoms of AD but the progression of the disease process as well.

Alzheimer Disease↗
PubMed1990

Cloning of a novel glutamate receptor subunit, GluR5: expression in the nervous system during development.

We have isolated cDNAs encoding a glutamate receptor subunit, designated GluR5, displaying 40%-41% amino acid identity with the kainate/AMPA receptor subunits GluR1, GluR2, GluR3, and GluR4. This level of sequence similarity is significantly below the approximately 70% intersubunit identity characteristic of kainate/AMPA receptors. The GluR5 protein forms homomeric ion channels in Xenopus oocytes that are weakly responsive to L-glutamate. The GluR5 gene is expressed in subsets of neurons throughout the developing and adult central and peripheral nervous systems. During embryogenesis, GluR5 transcripts are detected in areas of neuronal differentiation and synapse formation.

Aging↗
PubMed1989

Neuraxin, a novel putative structural protein of the rat central nervous system that is immunologically related to microtubule-associated protein 5.

During screening of a rat spinal cord lambda gt11 cDNA library with poly- and monoclonal antibodies against the postsynaptic glycine receptor a cDNA was isolated which covers an open reading frame encoding a protein of calculated mol. wt 94 kd. Sequence analysis identified a novel type of neuron-specific protein (named neuraxin) which is characterized by an unusual amino acid composition, 12 central heptadecarepeats and putative protein and/or membrane interaction sites. The gene encoding neuraxin appears to be unique in the haploid rat genome and conserved in higher vertebrates. Northern blot and in situ hybridization revealed neuraxin mRNA to be expressed throughout the rodent central nervous system (CNS). In spinal cord, neuraxin transcripts were abundant in motoneurons which also expressed glycine receptor subunit mRNA. A bacterial fusion protein containing approximately 90% of the neuraxin sequence was found to specifically bind tubulin. Polyclonal neuraxin antibodies cross-reacted with microtubule-associated protein 5 (MAP5), and a monoclonal antibody against MAP5 recognized the neuraxin fusion construct. Based on these data we suggest that neuraxin is related to MAP5 and may be implicated in neuronal membrane-microtubule interactions.

Amino Acid Sequence↗
PubMed1989

Central nicotinic acetylcholine receptors in the chicken and Drosophila CNS: biochemical and molecular biology approaches.

Putative neuronal nicotinic acetylcholine receptors (nAChRs) were investigated using biochemical and molecular biology approaches. In the chick visual system, a nicotinic cholinergic binding site was localized on a polypeptide of Mr 57,000 using the potent antagonist, alpha-bungarotoxin (alpha-Btx). Ion flux experiments indicate that this membrane protein is different from the toxin-insensitive nAChR present in vertebrate neurons. Crosshybridization with a Torpedo nAChR cDNA probe allowed isolation of a cholinergic receptor cDNA (ARD) from the Drosophila CNS. Analysis of the corresponding gene, its transcripts and the ARD protein are presented here.

Animals↗
PubMed1989

Neuronal acetylcholine receptors in Drosophila: mature and immature transcripts of the ard gene in the developing central nervous system.

The ARD protein is a Drosophila homolog of vertebrate nicotinic acetylcholine receptor (AChR) polypeptides. Here, an analysis of transcripts of the corresponding ard gene is presented. In situ hybridization experiments revealed ard gene expression in nervous tissue only. During development, ard transcripts are prevalent in late embryos, pupae, and newly eclosed flies. Both the spatial and the temporal pattern of ard gene expression is consistent with the ARD protein being part of a neuronal AChR that is produced in large amounts during major periods of neuronal differentiation. In situ hybridization with an intron-specific probe indicated codistribution of immature and mature ard RNAs in pupae and adult flies. In addition to the mature 3.2 kb RNA species, two large immature transcripts are found in newly eclosed flies but not in embryos, suggesting a developmentally regulated processing of ard RNA.

Animals↗
PubMed1988

Characterization of an invertebrate nicotinic acetylcholine receptor gene: the ard gene of Drosophila melanogaster.

The ard gene encodes a neuronal nicotinic acetylcholine receptor (AChR) protein from Drosophila (ARD protein). Cytogenetically this gene maps at position 64B/C on the left arm of the 3rd chromosome. Five introns interrupt the protein coding region of the gene, and one is found upstream of the translation start site. The ard gene thus contains less introns than vertebrate muscle AChR genes, but, with one exception, the positions of the resident introns are precisely conserved. Implications for the evolution of AChR genes are discussed.

Animals↗
PubMed1988

Neuronal acetylcholine receptors in Drosophila: the ARD protein is a component of a high-affinity alpha-bungarotoxin binding complex.

The ard gene of Drosophila melanogaster encodes a structural homologue of vertebrate nicotinic acetylcholine receptors (AChR) and is expressed exclusively in nervous tissue. To study the nature of the ARD protein, antibodies were raised against fusion constructs containing two regions of this polypeptide. One segment is putatively extracellular (amino acids 65-212), the other domain is exposed to the cytoplasm (amino acids 305-444). The ARD antisera obtained served to investigate the physical relationship between the ARD protein and alpha-bungarotoxin (alpha-Btx) binding sites occurring in Drosophila. Two different high-affinity binding sites for [125I]alpha-Btx, a highly potent antagonist of vertebrate muscle AChR, were detected in fly head membranes. Equilibrium binding and kinetic studies revealed Kd values of approximately 0.1 nM (site 1) and approximately 4 nM (site 2). The estimated maximal binding (Bmax) was approximately 240 and 1080 fmol/mg protein respectively. Both sites exhibited a nicotinic-cholinergic pharmacology. Immunoprecipitation experiments with the ARD antisera indicated that the ARD protein is associated with the [125I]alpha-Btx binding site 1 only. These data support the previously postulated hypothesis that the ARD protein is part of an alpha-Btx binding neuronal AChR of Drosophila. Furthermore, they indicate heterogeneity in nicotinic-cholinergic binding sites in the insect nervous system.

Animals↗
PubMed1987

Identification of gene products expressed in the developing chick visual system: characterization of a middle-molecular-weight neurofilament cDNA.

A cDNA library enriched for transcripts that accumulate from embryonic day 7 until day 1 posthatching was constructed from poly(A)+ RNA of chick optic lobe tissue. From this library, three recombinants were isolated that correspond to neural mRNAs appearing during the major period of synaptogenesis in the retinotectal system. One of these recombinants (OZ 11) was identified as a middle-molecular weight neurofilament (NF-M) cDNA which, together with two overlapping clones, encodes part of the rod and the entire tail region of NF-M. In situ hybridization revealed NF-M mRNA to be highly expressed in regions of the chick central nervous system, which contain multipolar and/or long-projection neurons.

Amino Acid Sequence↗
PubMed1986

Primary structure of a developmentally regulated nicotinic acetylcholine receptor protein from Drosophila.

Acetylcholine is a major excitatory neurotransmitter in the central nervous system of insects. Using DNA probes of the Torpedo nicotinic acetylcholine receptor (AChR) we have isolated two overlapping cDNA clones encoding a putative neuronal AChR protein from the fruitfly, Drosophila melanogaster. The predicted mature protein consists of 497 amino acids, has a calculated mol. wt of 57 340 and shows extensive homology to known AChR subunits from different species along its entire amino acid sequence. Northern analysis revealed a hybridizing mRNA of 3.2 kb in late embryo and in pupae. Expression of the corresponding AChR gene thus characterizes periods of neuronal differentiation in Drosophila.

Journal Article↗
PubMed1986

The glycine receptor deficiency of the mutant mouse spastic: evidence for normal glycine receptor structure and localization.

Homozygotes of the mutant mouse spastic exhibit reduced binding of 3H-strychnine to homogenates from various regions of the CNS compared with unaffected littermates (White and Heller, 1982). Here we report evidence that the spastic mutation coincides with a reduced concentration and an unaltered structure of the glycine receptor in spinal cord. Scatchard analysis of 3H-strychnine binding revealed a single binding site with a Bmax of 267 +/- 62 fmol/mg protein for spastic and of 864 +/- 220 fmol/mg protein for control mice; no difference was found for the corresponding KD values. Also Ki values of glycine for 3H-strychnine binding and displacement of 3H-strychnine by beta-alanine and taurine were indistinguishable for both preparations. Photoaffinity labeling of synaptic membranes with 3H-strychnine identified an Mr = 48,000 polypeptide in both control and spastic mouse membranes. Tryptic digestion of these membranes produced radiolabeled peptide fragments of identical molecular weights, suggesting that the proteolytic cleavage sites around the antagonist binding site are conserved in the mutant glycine receptor protein. Glycine receptors from both control and mutant mice were purified by affinity chromatography on aminostrychnine agarose. SDS/PAGE revealed three polypeptides of Mr = 48,000, 58,000, and 93,000 in both receptor preparations. Monoclonal antibodies directed against different subunits of the glycine receptor were applied to an enzyme-linked immunosorbent assay. The same pattern of immunoreactivity was obtained for glycine receptor from spinal cord of spastic homozygotes, control mice, and rats, suggesting conservation of the antigenic epitopes in the mutant receptor.(ABSTRACT TRUNCATED AT 250 WORDS)

Affinity Labels↗