Author
Harald Sontheimer
Other affiliations: Civitan International, University of Alabama at Birmingham, Veterans Health Administration ...read more
Bio: Harald Sontheimer is an academic researcher from Virginia Tech. The author has contributed to research in topics: Glioma & Astrocyte. The author has an hindex of 76, co-authored 232 publications receiving 17704 citations. Previous affiliations of Harald Sontheimer include Civitan International & University of Alabama at Birmingham.
Topics: Glioma, Astrocyte, Neuroglia, Glutamate receptor, Patch clamp
Papers published on a yearly basis
Papers
More filters
TL;DR: The isolation of a cloned cDNA encoding a new GABAA receptor subunit, termed γ2, which shares approximately 40% sequence identity with α-and β-subunits and whose messenger RNA is prominently localized in neuronal subpopulations throughout the CNS.
Abstract: NEUROTRANSMISSION effected by GABA (γ-aminobutyric acid) is predominantly mediated by a gated chloride channel intrinsic to the GABAA receptor. This heterooligomeric receptor1 exists in most inhibitory synapses in the vertebrate central nervous system (CNS) and can be regulated by clinically important compounds such as benzodiazepines and barbiturates2. The primary structures of GABAA receptor α- and β-subunits have been deduced from cloned complementary DNAs3,4. Co-expression of these subunits in heterologous systems generates receptors which display much of the pharmacology of their neural counterparts, including potentiation by barbiturates3–5. Conspicuously, however, they lack binding sites for, and consistent electrophysiological responses to, benzodiazepines4,5. We now report the isolation of a cloned cDNA encoding a new GABAA receptor subunit, termed γ2, which shares approximately 40% sequence identity with α-and β-subunits and whose messenger RNA is prominently localized in neuronal subpopulations throughout the CNS. Importantly, coexpression of the γ2 subunit with α1 and β1 subunits produces GABAA receptors displaying high-affinity binding for central benzodiazepine receptor ligands.
1,334 citations
Université Paris-Saclay1, Autonomous University of Barcelona2, University of Cambridge3, National Institute for Occupational Safety and Health4, University of Bonn5, German Center for Neurodegenerative Diseases6, Harvard University7, University of Lausanne8, National Research Council9, University of Padua10, Heidelberg University11, Salk Institute for Biological Studies12, University of Minnesota13, Pasteur Institute14, Tel Aviv University15, Johns Hopkins University16, University of Portsmouth17, Katholieke Universiteit Leuven18, PSL Research University19, Trinity College, Dublin20, Baylor College of Medicine21, University College London22, University of Edinburgh23, Oregon Health & Science University24, National Institutes of Health25, Columbia University26, University of Rochester27, University of Copenhagen28, Ludwig Maximilian University of Munich29, University of Málaga30, Tufts University31, University of Freiburg32, Utrecht University33, Nihon University34, Max Delbrück Center for Molecular Medicine35, University of California, Los Angeles36, University of Yamanashi37, New York University38, University of British Columbia39, King Abdullah University of Science and Technology40, University of Wisconsin-Madison41, University of California, San Francisco42, McGill University43, University of Kentucky44, Kyushu University45, University of Bordeaux46, Polytechnic Institute of Cávado and Ave47, University of Minho48, University of Alabama at Birmingham49, University of Gothenburg50, University of Poitiers51, Cajal Institute52, King's College London53, University of Strasbourg54, Virginia Tech55, University of Düsseldorf56, I.M. Sechenov First Moscow State Medical University57, Russian Academy of Sciences58, University of Seville59, Georgia Institute of Technology60, University of Texas Health Science Center at Houston61, University of California, San Diego62, Universidade Federal do Rio Grande do Sul63, University of Ljubljana64, Ikerbasque65, University of Manchester66
TL;DR: In this article, the authors point out the shortcomings of binary divisions of reactive astrocytes into good-vs-bad, neurotoxic vs-neuroprotective or A1-vs.A2.
Abstract: Reactive astrocytes are astrocytes undergoing morphological, molecular, and functional remodeling in response to injury, disease, or infection of the CNS. Although this remodeling was first described over a century ago, uncertainties and controversies remain regarding the contribution of reactive astrocytes to CNS diseases, repair, and aging. It is also unclear whether fixed categories of reactive astrocytes exist and, if so, how to identify them. We point out the shortcomings of binary divisions of reactive astrocytes into good-vs-bad, neurotoxic-vs-neuroprotective or A1-vs-A2. We advocate, instead, that research on reactive astrocytes include assessment of multiple molecular and functional parameters-preferably in vivo-plus multivariate statistics and determination of impact on pathological hallmarks in relevant models. These guidelines may spur the discovery of astrocyte-based biomarkers as well as astrocyte-targeting therapies that abrogate detrimental actions of reactive astrocytes, potentiate their neuro- and glioprotective actions, and restore or augment their homeostatic, modulatory, and defensive functions.
797 citations
TL;DR: The unique biology of glioma invasion provides hitherto unexplored brain-specific therapeutic targets for this devastating disease.
Abstract: Malignant gliomas are devastating tumours that frequently kill patients within 1 year of diagnosis. The major obstacle to a cure is diffuse invasion, which enables tumours to escape complete surgical resection and chemo- and radiation therapy. Gliomas use the same tortuous extracellular routes of migration that are travelled by immature neurons and stem cells, frequently using blood vessels as guides. They repurpose ion channels to dynamically adjust their cell volume to accommodate to narrow spaces and breach the blood-brain barrier through disruption of astrocytic endfeet, which envelop blood vessels. The unique biology of glioma invasion provides hitherto unexplored brain-specific therapeutic targets for this devastating disease.
577 citations
TL;DR: Cellular localization of the mRNAs encoding the gamma 2 and delta subunits in rat brain revealed that largely distinct neuronal subpopulations express the two subunits, implications for the composition of two different GABAA receptor subtypes and for information processing in networks using GABA for signaling.
553 citations
Journal Article•
TL;DR: Interestingly, several phenylglycine derivatives including the metabotropic glutamate receptor agonist/antagonist (S)-4-carboxyphenyl glycine (S-4CPG) potently and selectively inhibited glutamate release from glioma cells and prevented neurotoxicity, which suggests that neurotoxic release of glutamate by gliomas may be prevented by phenyl glucose derivatives, which may thus be useful as an adjuvant treatment for brain tumors.
Abstract: Elevated levels of extracellular glutamate ([Glu] o ) cause uncontrolledCa 21 increases in most neurons and are believed to mediate excitotoxicbrain injury following stroke and other nervous system insults. In thenormal brain, [Glu] o is tightly controlled by uptake into astrocytes. Be-cause the vast majority of primary brain tumors (gliomas) are derivedfrom astrocytes, we investigated glutamate uptake in glioma cells surgi-cally isolated from glioma patients (glioblastoma multiforme) and in sevenestablished human glioma cell lines, including STTG-1, D -54 MG, D -65MG, U-373 MG, U-138 MG, U-251 MG, and CH-235 MG. All glioma cellsstudied showed impaired glutamate uptake, with a V max < 10% that ofnormal astrocytes. Moreover, rather than removing glutamate from theextracellular fluid, glioma cells release large amounts of glutamate, re-sulting in elevations of [Glu] o in excess of 100 m M within hours in a spacethat is 1000-fold larger than the cellular volume. Exposure of culturedhippocampal neurons to glioma-conditioned medium elicited sustained[Ca
411 citations
Cited by
More filters
TL;DR: This review describes the members of the matrixin family and discusses substrate specificity, domain structure and function, the activation of proMMPs, the regulation of matrixin activity by tissue inhibitors of metalloproteinases, and their pathophysiological implication.
Abstract: Matrix metalloproteinases (MMPs), also designated matrixins, hydrolyze components of the extracellular matrix. These proteinases play a central role in many biological processes, such as embryogenesis, normal tissue remodeling, wound healing, and angiogenesis, and in diseases such as atheroma, arthritis, cancer, and tissue ulceration. Currently 23 MMP genes have been identified in humans, and most are multidomain proteins. This review describes the members of the matrixin family and discusses substrate specificity, domain structure and function, the activation of proMMPs, the regulation of matrixin activity by tissue inhibitors of metalloproteinases, and their pathophysiological implication.
4,411 citations
TL;DR: Astrocyte functions in healthy CNS, mechanisms and functions of reactive astrogliosis and glial scar formation, and ways in which reactive astrocytes may cause or contribute to specific CNS disorders and lesions are reviewed.
Abstract: Astrocytes are specialized glial cells that outnumber neurons by over fivefold. They contiguously tile the entire central nervous system (CNS) and exert many essential complex functions in the healthy CNS. Astrocytes respond to all forms of CNS insults through a process referred to as reactive astrogliosis, which has become a pathological hallmark of CNS structural lesions. Substantial progress has been made recently in determining functions and mechanisms of reactive astrogliosis and in identifying roles of astrocytes in CNS disorders and pathologies. A vast molecular arsenal at the disposal of reactive astrocytes is being defined. Transgenic mouse models are dissecting specific aspects of reactive astrocytosis and glial scar formation in vivo. Astrocyte involvement in specific clinicopathological entities is being defined. It is now clear that reactive astrogliosis is not a simple all-or-none phenomenon but is a finely gradated continuum of changes that occur in context-dependent manners regulated by specific signaling events. These changes range from reversible alterations in gene expression and cell hypertrophy with preservation of cellular domains and tissue structure, to long-lasting scar formation with rearrangement of tissue structure. Increasing evidence points towards the potential of reactive astrogliosis to play either primary or contributing roles in CNS disorders via loss of normal astrocyte functions or gain of abnormal effects. This article reviews (1) astrocyte functions in healthy CNS, (2) mechanisms and functions of reactive astrogliosis and glial scar formation, and (3) ways in which reactive astrocytes may cause or contribute to specific CNS disorders and lesions.
4,075 citations
TL;DR: The estimates of energy usage predict the use of distributed codes, with ≤15% of neurons simultaneously active, to reduce energy consumption and allow greater computing power from a fixed number of neurons.
Abstract: Anatomic and physiologic data are used to analyze the energy expenditure on different components of excitatory signaling in the grey matter of rodent brain. Action potentials and postsynaptic effects of glutamate are predicted to consume much of the energy (47% and 34%, respectively), with the resting potential consuming a smaller amount (13%), and glutamate recycling using only 3%. Energy usage depends strongly on action potential rate--an increase in activity of 1 action potential/cortical neuron/s will raise oxygen consumption by 145 mL/100 g grey matter/h. The energy expended on signaling is a large fraction of the total energy used by the brain; this favors the use of energy efficient neural codes and wiring patterns. Our estimates of energy usage predict the use of distributed codes, with
2,912 citations
TL;DR: Cloning of a complementary DNA for brain nitric oxide synthase reveals recognition sites for NADPH, FAD, flavin mononucleotide and calmodulin as well as phosphorylation sites, indicating that the synthase is regulated by many different factors.
Abstract: Nitric oxide is a messenger molecule, mediating the effect of endothelium-derived relaxing factor in blood vessels and the cytotoxic actions of macrophages, and playing a part in neuronal communication in the brain. Cloning of a complementary DNA for brain nitric oxide synthase reveals recognition sites for NADPH, FAD, flavin mononucleotide and calmodulin as well as phosphorylation sites, indicating that the synthase is regulated by many different factors. The only known mammalian enzyme with close homology is cytochrome P-450 reductase.
2,302 citations
TL;DR: A background on applications of MNPs as MR imaging contrast agents and as carriers for drug delivery and an overview of the recent developments in this area of research are provided.
2,295 citations