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M G Erlander

Publications and source records attributed to M G Erlander.

34 records · Page 2Linked to original sources
PubMed1993

Two members of a distinct subfamily of 5-hydroxytryptamine receptors differentially expressed in rat brain.

We report two serotonin (5-hydroxytryptamine, 5-HT) receptors, MR22 and REC17, that belong to the G-protein-associated receptor superfamily. MR22 and REC17 are 371 and 357 amino acids long, respectively, as deduced from nucleotide sequence and share 68% mutual amino acid identity and 30-35% identity with known catecholamine and 5-HT receptors. Saturable binding of 125I-labeled (+)-lysergic acid diethylamide to transiently expressed MR22 in COS-M6 cells was inhibited by ergotamine > methiothepin > 5-carboxamidotryptamine > 5-HT. For REC17, the rank of potency was ergotamine > 5-carboxamidotryptamine > methiothepin > methysergide > 5-HT. Both were insensitive to 5-HT1A, 5-HT1D or 5-HT2 serotonergic ligands [8-hydroxy-2-(di-n-propylamino)tetralin, sumatriptan, and 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane]. The mRNAs encoding MR22 were detected in the CA1 region of hippocampus, the medial habenula, and raphe nuclei. In contrast, mRNAs encoding REC17 were found throughout the rat central nervous system. We propose that REC17 and MR22, designated as 5-HT5 alpha and 5-HT5 beta, represent a distinct subfamily of 5-HT receptors.

Amino Acid Sequence↗
PubMed1993

Molecular cloning and functional expression of 5-HT1E-like rat and human 5-hydroxytryptamine receptor genes.

Sequential polymerase chain reaction experiments were performed to amplify a unique sequence representing a guanine nucleotide-binding protein (G-protein)-coupled receptor from rat hypothalamic cDNA. Degenerate oligonucleotides corresponding to conserved amino acids from transmembrane domains III, V, and VI of known receptors [5-HT1A, 5-HT1C, and 5-HT2; 5-HT is serotonin (5-hydroxytryptamine)] were used as primers for the sequential reactions. The resulting product was subcloned and used to screen a rat genomic library to identify a full-length clone (MR77) containing an intronless open reading frame encoding a 366-amino acid seven-transmembrane domain protein. The human homolog was isolated, and its encoded protein had 93% overall amino acid identity with the rat sequence. Within the conserved transmembrane domains, the sequences exhibit approximately 52%, 59%, 65%, and 68% amino acid identity with the known rat 5-HT1A, rat 5-HT1B, rat 5-HT1D, and human 5-HT1E receptors, respectively. MR77 was subcloned into a eukaryotic expression vector system and expressed in CosM6 cells. Studies on broken cell preparations indicate that the expressed receptor exhibits 125I-labeled d-lysergic acid diethylamide (LSD) binding that can be displaced by serotonin but not by other biogenic amines. The specific binding is displaced by the selective 5-HT1D agonist sumatriptan but not by the mixed 5-HT1A/1D agonist 5-carboxyamidotryptamine. 125I-labeled LSD binding was competitively antagonized by the ergot alkaloids methysergide and ergotamine. HeLa cells transfected with the MR77 gene exhibited inhibition of adenylate cyclase in response to serotonin. MR77 is expressed at low levels throughout the brain, with the greatest expression in the cortex, hippocampus, and striatum. MR77 thus represents a 5-HT receptor of the 5-HT1 class, and we propose that, based on the pharmacological characterization, MR77 represents an additional 5-HT1E-like receptor.

Amino Acid Sequence↗
PubMed1993

Molecular approach to hypothalamic rhythms: isolation of novel indoleamine receptor genes.

We have utilized polymerase chain reaction with primers corresponding to conserved amino acid sequences within membrane-spanning regions of known serotonin receptors to identify clones of four putative new indoleamine receptors. We have determined complete amino acid sequences of these four receptors, which fall into three subfamilies; two of these subfamilies are novel. The sites of expression within the brain have been determined for each of the genes. Expression in mammalian cells demonstrates that each new protein is a receptor for serotonin and that each has a distinct pharmacology when compared to known receptors. Two of the new receptors are coupled to cyclic adenosine monophosphate, one negatively (Gi) and one positively (Gs). The latter is a candidate for the serotonin receptor that mediates phase advances in circadian rhythms of the suprachiasmatic nucleus.

Animals↗
PubMed1992

Comparative distribution of messenger RNAs encoding glutamic acid decarboxylases (Mr 65,000 and Mr 67,000) in the basal ganglia of the rat.

Glutamic acid decarboxylase, the enzyme required for GABA synthesis, exists as distinct isoforms, which have recently been found to be encoded by different genes. The relative expression of messenger RNAs encoding two isoforms of glutamic acid decarboxylase (Mr 67,000 and Mr 65,000) was measured at the single-cell level in neurons of the rat basal ganglia with in situ hybridization histochemistry. Both messenger RNAs were expressed in neurons of the striatum, pallidum, and substantia nigra pars reticulata, but marked differences in the relative level of labelling were observed with the two probes. In striatum, efferent neurons were more densely labelled for the messenger RNA encoding glutamic acid decarboxylase (Mr 65,000) than for the messenger RNA encoding glutamic acid decarboxylase (Mr 67,000), whereas the reverse was observed for GABA-ergic interneurons. Neurons of the entopeduncular nucleus were much more densely labelled for messenger RNA encoding glutamic acid decarboxylase (Mr 65,000) than for messenger RNA encoding glutamic acid decarboxylase (Mr 67,000). In addition, labelling for messenger RNA encoding glutamic acid decarboxylase (Mr 65,000) was higher in the entopeduncular nucleus (internal pallidum) than in the globus pallidus (external pallidum), a structure which expressed similar levels of both mRNAs. In contrast to neurons of the internal pallidum, efferent neurons of the substantia nigra pars reticulata expressed slightly more messenger RNA encoding glutamic acid decarboxylase (Mr 67,000) than that encoding the other isoform of the enzyme. The results suggest a differential expression of the messenger RNAs encoding the two isoforms of glutamic acid decarboxylase in subpopulations of basal ganglia neurons in rats.

Animals↗
PubMed1992

Two human glutamate decarboxylases, 65-kDa GAD and 67-kDa GAD, are each encoded by a single gene.

We report the isolation and sequencing of cDNAs encoding two human glutamate decarboxylases (GADs; L-glutamate 1-carboxy-lyase, EC 4.1.1.15), GAD65 and GAD67. Human GAD65 cDNA encodes a Mr 65,000 polypeptide, with 585 amino acid residues, whereas human GAD67 encodes a Mr 67,000 polypeptide, with 594 amino acid residues. Both cDNAs direct the synthesis of enzymatically active GADs in bacterial expression systems. Each cDNA hybridizes to a single species of brain mRNA and to a specific set of restriction fragments in human genomic DNA. In situ hybridization of fluorescently labeled GAD probes to human chromosomes localizes the human GAD65 gene to chromosome 10p11.23 and the human GAD67 gene to chromosome 2q31. We conclude that GAD65 and GAD67 each derive from a single separate gene. The cDNAs we describe should allow the bacterial production of test antigens for the diagnosis and prediction of insulin-dependent diabetes mellitus.

Amino Acid Sequence↗
PubMed1992

Response of peripheral-blood mononuclear cells to glutamate decarboxylase in insulin-dependent diabetes.

Insulin-dependent diabetes is characterised by autoantibodies to several pancreatic-islet-cell antigens, including glutamate decarboxylase. We measured the proliferative responses to this antigen of peripheral-blood mononuclear cells from patients with newly diagnosed insulin-dependent diabetes, relatives of diabetic patients, and healthy controls. The likelihood of a positive response was substantially greater among the diabetic patients and relatives positive for islet-cell autoantibodies (ICA) than among subjects at low risk of diabetes (controls and ICA-negative relatives). Glutamate decarboxylase may have a pathogenetic role in insulin-dependent diabetes.

Autoantibodies↗
PubMed1992

Transient increase in expression of a glutamate decarboxylase (GAD) mRNA during the postnatal development of the rat striatum.

We recently reported that the mammalian brain has two forms of the GABA synthetic enzyme glutamate decarboxylase (GAD, E.C. 4.1.1.15), which are the products of two genes. The two forms, which we call GAD65 and GAD67, differ from each other in sequence, molecular size, subcellular distribution, and interactions with the cofactor pyridoxal phosphate (PLP), with GAD65 activity more dependent than that of GAD67 on the continued presence of exogenous PLP. The existence of two GAD genes suggests that individual GABA neurons may be subject to differential regulation of GABA production. We have examined the expression of these two forms of GAD during postnatal development of the rat striatum to determine whether different classes of GABA neurons selectively express different amounts of the two GAD mRNAs. Here we present evidence for a dramatic developmental difference in the expression of the two mRNAs during postnatal development of the rat striatum. Using in situ hybridization to the two GAD mRNAs, we observed a selective increase in GAD65 mRNA during the second postnatal week, at the time when striatal matrix neurons innervate the substantia nigra (SN). PLP-dependent enzyme activity in the midbrain increases in parallel with increased expression of GAD65 mRNA in the striatum. We hypothesize that the innervation of the SN by striatal neurons triggers an increase in GAD65. The changing ratios of GAD65 and GAD67 in the striatum may contribute to the well-documented changes in seizure susceptibility that occur in early life.

Animals↗
PubMed1992

Glutamate decarboxylases in nonneural cells of rat testis and oviduct: differential expression of GAD65 and GAD67.

gamma-Aminobutyric acid (GABA) and its synthetic enzyme, glutamate decarboxylase (GAD), are not limited to the nervous system but are also found in nonneural tissues. The mammalian brain contains at least two forms of GAD (GAD67 and GAD65), which differ from each other in size, sequence, immunoreactivity, and their interaction with the cofactor pyridoxal 5'-phosphate (PLP). We used cDNAs and antibodies specific to GAD65 and GAD67 to study the molecular identity of GADs in peripheral tissues. We detected GAD and GAD mRNAs in rat oviduct and testis. In oviduct, the size of GAD, its response to PLP, its immunoreactivity, and its hybridization to specific RNA and DNA probes all indicate the specific expression of the GAD65 gene. In contrast, rat testis expresses the GAD67 gene. The GAD in these two reproductive tissues is not in neurons but in nonneural cells. The localization of brain GAD and GAD mRNAs in the mucosal epithelial cells of the oviduct and in spermatocytes and spermatids of the testis shows that GAD is not limited to neurons and that GABA may have functions other than neurotransmission.

Animals↗
PubMed1992

A transcriptional regulatory element of the gene encoding the 67,000-M(r) form of human glutamate decarboxylase is similar to a Drosophila regulatory element.

We have isolated the 5' flanking DNA sequences of the human gene encoding the 67,000-M(r) form of glutamate decarboxylase (GAD67), the gamma-aminobutyric acid synthetic enzyme. Transcription begins at a single promoter (P1) in adult brain but at two tandem promoters, P1 and P2, in fetal brain. P1, which is 3' to P2, resembles the promoter regions of many constitutively expressed genes, whereas P2 resembles a tissue-specific promoter. P1 contains a 10-base sequence (dec-1) that closely matches the element I cis-regulatory sequence identified in the promoter region of Drosophila 3,4-dihydroxyphenylalanine decarboxylase. Gel shift and transient expression assays demonstrate that the dec-1 sequence plays a role in the transcription of the human GAD67 gene.

Animals↗
PubMed1992

Autoimmunity to two forms of glutamate decarboxylase in insulin-dependent diabetes mellitus.

Insulin-dependent diabetes mellitus (IDDM) is thought to result from the autoimmune destruction of the insulin-producing beta cells of the pancreas. Years before IDDM symptoms appear, we can detect autoantibodies to one or both forms of glutamate decarboxylase (GAD65 and GAD67), synthesized from their respective cDNAs in a bacterial expression system. Individual IDDM sera show distinctive profiles of epitope recognition, suggesting different humoral immune responses. Although the level of GAD autoantibodies generally decline after IDDM onset, patients with IDDM-associated neuropathies have high levels of antibodies to GAD, years after the appearance of clinical IDDM. We note a striking sequence similarity between the two GADs and Coxsackievirus, a virus that has been associated with IDDM both in humans and in experimental animals. This similarity suggests that molecular mimicry may play a role in the pathogenesis of IDDM.

Amino Acid Sequence↗
PubMed1991

The structural and functional heterogeneity of glutamic acid decarboxylase: a review.

Studies of the GABA-synthetic enzyme glutamate decarboxylase (glutamic acid decarboxylase; GAD; E.C.4.1.1.15) began in 1951 with the work of Roberts and his colleagues. Since then, many investigators have demonstrated the structural and functional heterogeneity of brain GAD. At least part of this heterogeneity derives from the existence of two GAD genes.

Animals↗
PubMed1991

Postnatal expression of glutamate decarboxylases in developing rat cerebellum.

The recent identification of two genes encoding distinct forms of the GABA synthetic enzyme, glutamate decarboxylase (GAD), raises the possibility that varying expression of the two genes may contribute to the regulation of GABA production in individual neurons. We investigated the postnatal development the two forms of GAD in the rat cerebellum. The mRNA for GAD67, the form which is less dependent on the presence of the cofactor, pyridoxal phosphate (PLP), is present at birth in presumptive Purkinje cells and increases during postnatal development. GAD67 mRNA predominates in the cerebellum. The mRNA for GAD65, which displays marked PLP-dependence for enzyme activity, cannot be detected in cerebellar cortex by in situ hybridization until P7 in Purkinje cells, and later in other GABA neurons. In deep cerebellar nuclei, which mature prenatally, both forms of GAD mRNA can be detected at birth. The amounts of immunoreactice GAD and GAD enzyme activity parallel changes in mRNA levels. We suggest that the delayed appearance of GAD65 is coincident with synapse formation between GABA neurons and their targets during the second postnatal week. GAD67 mRNA may be present prior to synaptogenesis to produce GABA for trophic and metabolic functions.

Aging↗
PubMed1991

Two genes encode distinct glutamate decarboxylases.

gamma-Aminobutyric acid (GABA) is the most widely distributed known inhibitory neurotransmitter in the vertebrate brain. GABA also serves regulatory and trophic roles in several other organs, including the pancreas. The brain contains two forms of the GABA synthetic enzyme glutamate decarboxylase (GAD), which differ in molecular size, amino acid sequence, antigenicity, cellular and subcellular location, and interaction with the GAD cofactor pyridoxal phosphate. These forms, GAD65 and GAD67, derive from two genes. The distinctive properties of the two GADs provide a substrate for understanding not only the multiple roles of GABA in the nervous system, but also the autoimmune response to GAD in insulin-dependent diabetes mellitus.

Amino Acid Sequence↗
PubMed1985

Effects of L-dopa supplementation on concentrations of brain catechols, dopamine receptor binding and the incidence of pale, soft and exudative meat in stress-susceptible pigs.

The purpose of this research was to determine if chronic dietary L-DOPA supplementation will alter differentially the brain catechol concentrations, dopamine receptor binding (KD and Bmax) and the incidence of pale, soft and exudative (PSE) meat in stress-susceptible (SS) and stress-resistant (SR) pigs. Stress-susceptible and SR pigs were assigned randomly to these four groups: SS pigs as controls, SR pigs as controls, SS pigs with L-DOPA supplementation and SR pigs with L-DOPA supplementation. The experiment began when pigs weighed 23 kg and terminated when pigs weighed 95 kg. Anatomical brain structures removed at slaughter included hypothalamus, thalamus, cortex, cerebellum, olfactory bulb, caudate nucleus, putamen and substantia nigra. Concentrations of norepinephrine and dopamine were greater in the hypothalami of SS than of SR control pigs. The L-DOPA supplementation eliminated the strain differences of brain catecholamine concentrations. Pigs fed L-DOPA had greater concentrations of dihydroxyphenylacetic acid in six of the eight brain regions analyzed than the controls. Dopamine receptor binding (Bmax and KD) of spiroperidol was similar in all four groups of pigs. Pale, soft and exudative pork developed to the same extent in SS pigs with or without L-DOPA treatment. The results suggest that L-DOPA supplementation eliminates strain differences in brain catecholamine concentrations but does not alter PSE meat development or striatal dopamine receptor binding.

3,4-Dihydroxyphenylacetic Acid↗