The Experts below are selected from a list of 9174 Experts worldwide ranked by ideXlab platform
Adam Sapirstein - One of the best experts on this subject based on the ideXlab platform.
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Astrocyte Inositol Triphosphate Receptor Type 2 and Cytosolic Phospholipase A2 Alpha Regulate Arteriole Responses in Mouse Neocortical Brain Slices
2016Co-Authors: David J Linden, Adam SapirsteinAbstract:Functional hyperemia of the cerebral vascular system matches regional blood flow to the metabolic demands of the brain. One current model of neurovascular control holds that glutamate released by neurons activates group I metabotropic glutamate Receptors (mGluRs) on astrocytes, resulting in the production of diffusible messengers that act to regulate smooth muscle cells surrounding cerebral arterioles. The acute mouse brain slice is an experimental system in which changes in arteriole diameter can precisely measured with light microscopy. Stimulation of the brain slice triggers specific cellular responses that can be correlated to changes in arteriole diameter. Here we used Inositol Trisphosphate Receptor type 2 (IP3R2) and cytosolic phospholipase A2 alpha (cPLA2a) deficient mice to determine if astrocyte mGluR activation coupled to IP3R2-mediated Ca 2+ release and subsequent cPLA2a activation is required for arteriole regulation. We measured changes in astrocyte cytosolic free Ca2+ and arteriole diameters in response to mGluR agonist or electrical field stimulation in acute neocortical mouse brain slices maintained in 95 % or 20 % O2. Astrocyte Ca 2+ and arteriole responses to mGluR activation were absent in IP3R2 2/2 slices. Astrocyte Ca2+ responses to mGluR activation were unchanged by deletion of cPLA2a bu
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astrocyte Inositol triphosphate Receptor type 2 and cytosolic phospholipase a2 alpha regulate arteriole responses in mouse neocortical brain slices
PLOS ONE, 2012Co-Authors: Lihua He, David J Linden, Adam SapirsteinAbstract:Functional hyperemia of the cerebral vascular system matches regional blood flow to the metabolic demands of the brain. One current model of neurovascular control holds that glutamate released by neurons activates group I metabotropic glutamate Receptors (mGluRs) on astrocytes, resulting in the production of diffusible messengers that act to regulate smooth muscle cells surrounding cerebral arterioles. The acute mouse brain slice is an experimental system in which changes in arteriole diameter can precisely measured with light microscopy. Stimulation of the brain slice triggers specific cellular responses that can be correlated to changes in arteriole diameter. Here we used Inositol Trisphosphate Receptor type 2 (IP3R2) and cytosolic phospholipase A2 alpha (cPLA2α) deficient mice to determine if astrocyte mGluR activation coupled to IP3R2-mediated Ca2+ release and subsequent cPLA2α activation is required for arteriole regulation. We measured changes in astrocyte cytosolic free Ca2+ and arteriole diameters in response to mGluR agonist or electrical field stimulation in acute neocortical mouse brain slices maintained in 95% or 20% O2. Astrocyte Ca2+ and arteriole responses to mGluR activation were absent in IP3R2−/− slices. Astrocyte Ca2+ responses to mGluR activation were unchanged by deletion of cPLA2α but arteriole responses to either mGluR agonist or electrical stimulation were ablated. The valence of changes in arteriole diameter (dilation/constriction) was dependent upon both stimulus and O2 concentration. Neuron-derived NO and activation of the group I mGluRs are required for responses to electrical stimulation. These findings indicate that an mGluR/IP3R2/cPLA2α signaling cascade in astrocytes is required to transduce neuronal glutamate release into arteriole responses.
Alan T Nurden - One of the best experts on this subject based on the ideXlab platform.
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impaired megakaryocytopoiesis in type 2b von willebrand disease with severe thrombocytopenia
Blood, 2006Co-Authors: Paquita Nurden, William Vainchenker, Najet Debili, D. Meyer, Regis Bobe, Raymonde Bredoux, Elisabeth Corvazier, Robert Combrie, Edith Fressinaud, Alan T NurdenAbstract:In type 2B von Willebrand disease, there is spontaneous binding of mutated von Willebrand factor (VWF) multimers to platelets. Here we report a family in which severe thrombocytopenia may also be linked to abnormal megakaryocytopoiesis. A heterozygous mutation in the VWF A1 domain gave a R1308P substitution in an interactive site for glycoprotein Ibα (GPIbα). Electron microscopy showed clusters of platelets in close contact. Binding of antibodies to the GPIbα N-terminal domain was decreased, whereas GPIX and GPV were normally detected. In Western blotting (WB), GPIbα, αIIb, and β3 were normally present. Proteins involved in Ca 2+ homeostasis were analyzed by quantitating platelet mRNA or by WB. Plasma membrane Ca 2+ ATPase (PMCA)-4b and type III Inositol Trisphosphate Receptor (InsP 3 -R3) were selectively increased. The presence of degradation products of polyadenosine diphosphate (ADP)-ribose polymerase protein (PARP) suggested ongoing caspase-3 activity. These were findings typical of immature normal megakaryocytes cultured from peripheral blood CD34 + cells with TPO. Significantly, megakaryocytes from the patients in culture produced self-associated and interwoven proplatelets. Immunolocalization showed VWF not only associated with platelets, but already on the megakaryocyte surface and within internal channels. In this family, type 2B VWD is clearly associated with abnormal platelet production.
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impaired megakaryocytopoiesis in type 2b von willebrand disease with severe thrombocytopenia
Blood, 2006Co-Authors: Paquita Nurden, William Vainchenker, Najet Debili, D. Meyer, Regis Bobe, Raymonde Bredoux, Elisabeth Corvazier, Robert Combrie, Edith Fressinaud, Alan T NurdenAbstract:In type 2B von Willebrand disease, there is spontaneous binding of mutated von Willebrand factor (VWF) multimers to platelets. Here we report a family in which severe thrombocytopenia may also be linked to abnormal megakaryocytopoiesis. A heterozygous mutation in the VWF A1 domain gave a R1308P substitution in an interactive site for glycoprotein Ibα (GPIbα). Electron microscopy showed clusters of platelets in close contact. Binding of antibodies to the GPIbα N-terminal domain was decreased, whereas GPIX and GPV were normally detected. In Western blotting (WB), GPIbα, αIIb, and β3 were normally present. Proteins involved in Ca 2+ homeostasis were analyzed by quantitating platelet mRNA or by WB. Plasma membrane Ca 2+ ATPase (PMCA)-4b and type III Inositol Trisphosphate Receptor (InsP 3 -R3) were selectively increased. The presence of degradation products of polyadenosine diphosphate (ADP)-ribose polymerase protein (PARP) suggested ongoing caspase-3 activity. These were findings typical of immature normal megakaryocytes cultured from peripheral blood CD34 + cells with TPO. Significantly, megakaryocytes from the patients in culture produced self-associated and interwoven proplatelets. Immunolocalization showed VWF not only associated with platelets, but already on the megakaryocyte surface and within internal channels. In this family, type 2B VWD is clearly associated with abnormal platelet production.
Ken Mackie - One of the best experts on this subject based on the ideXlab platform.
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the cannabinoid agonist win55 212 2 increases intracellular calcium via cb1 Receptor coupling to gq 11 g proteins
Proceedings of the National Academy of Sciences of the United States of America, 2005Co-Authors: Jane E Lauckner, Bertil Hille, Ken MackieAbstract:Central nervous system responses to cannabis are primarily mediated by CB1 Receptors, which couple preferentially to Gi/o G proteins. Here, we used calcium photometry to monitor the effect of CB1 activation on intracellular calcium concentration. Perfusion with 5 μM CB1 aminoalkylindole agonist, WIN55,212-2 (WIN), increased intracellular calcium by several hundred nanomolar in human embryonic kidney 293 cells stably expressing CB1 and in cultured hippocampal neurons. The increase was blocked by coincubation with the CB1 antagonist, SR141716A, and was absent in nontransfected human embryonic kidney 293 cells. The calcium rise was WIN-specific, being essentially absent in cells treated with other classes of cannabinoid agonists, including Δ9-tetrahydrocannabinol, HU-210, CP55,940, 2-arachidonoylglycerol, methanandamide, and cannabidiol. The increase in calcium elicited by WIN was independent of Gi/o, because it was present in pertussis toxin-treated cells. Indeed, pertussis toxin pretreatment enhanced the potency and efficacy of WIN to increase intracellular calcium. The calcium increases appeared to be mediated by Gq G proteins and phospholipase C, because they were markedly attenuated in cells expressing dominant-negative Gq or treated with the phospholipase C inhibitors U73122 and ET-18-OCH3 and were accompanied by an increase in Inositol phosphates. The calcium increase was blocked by the sarco/endoplasmic reticulum Ca2+ pump inhibitor thapsigargin, the Inositol Trisphosphate Receptor inhibitor xestospongin D, and the ryanodine Receptor inhibitors dantrolene and 1,1′-diheptyl-4,4′-bipyridinium dibromide, but not by removal of extracellular calcium, showing that WIN releases calcium from intracellular stores. In summary, these results suggest that WIN stabilizes CB1 Receptors in a conformation that enables Gq signaling, thus shifting the G protein specificity of the Receptor.
Carl White - One of the best experts on this subject based on the ideXlab platform.
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apoptosis protection by mcl 1 and bcl 2 modulation of Inositol 1 4 5 Trisphosphate Receptor dependent ca2 signaling
Journal of Biological Chemistry, 2010Co-Authors: Emily F Eckenrode, Kevin J Foskett, Jun Yang, G V Velmurugan, Carl WhiteAbstract:Members of the Bcl-2 protein family play a central role in the regulation of apoptosis. An interaction between anti-apoptotic Bcl-xL and the endoplasmic reticulum (ER)-localized Inositol Trisphosphate Receptor Ca2+ release channel (InsP3R) enables Bcl-xL to be fully efficacious as an anti-apoptotic mediator (White, C., Li, C., Yang, J., Petrenko, N. B., Madesh, M., Thompson, C. B., and Foskett, J. K. (2005) Nat. Cell Biol. 7, 1021–1028). Physiologically, Bcl-xL binds to the InsP3R to enhance its gating and Ca2+ signaling. Here we have discovered that structurally related proteins Bcl-2 and Mcl-1 function similarly. Bcl-2, Mcl-1 and Bcl-xL bind with comparable affinity to the carboxyl termini of all three mammalian InsP3R isoforms with important functional consequences. Stable expression of Bcl-2 or Mcl-1 lowered ER Ca2+ content and enhanced the rate of InsP3-mediated Ca2+ release in response to submaximal InsP3 stimulation in permeabilized wild-type DT40 cells but not in cells lacking InsP3R. In addition, expression of either Bcl-2 or Mcl-1 enhanced spontaneous InsP3R-dependent Ca2+ oscillations and spiking in intact cells in the absence of agonist stimulation. Bcl-2- and Mcl-1-mediated protection from apoptosis induced by staurosporine or etoposide was enhanced in cells expressing InsP3R, demonstrating that their interactions with InsP3R enable Bcl-2 and Mcl-1 to be fully efficacious anti-apoptotic mediators. Our data suggest a molecular mechanism that is shared by several anti-apoptotic Bcl-2 proteins that provides apoptosis resistance by direct interactions at the ER with the InsP3R that impinges on cellular Ca2+ homeostasis.
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apoptosis regulation by bcl xl modulation of mammalian Inositol 1 4 5 Trisphosphate Receptor channel isoform gating
Proceedings of the National Academy of Sciences of the United States of America, 2007Co-Authors: Xiaoli Wang, Kevin J Foskett, Horia Vais, Craig B Thompson, Carl WhiteAbstract:Members of the Bcl-2 family of proteins regulate apoptosis, with some of their physiological effects mediated by their modulation of endoplasmic reticulum (ER) Ca2+ homeostasis. Antiapoptotic Bcl-xL binds to the Inositol Trisphosphate Receptor (InsP3R) Ca2+ release channel to enhance Ca2+- and InsP3-dependent regulation of channel gating, resulting in reduced ER [Ca2+], increased oscillations of cytoplasmic Ca2+ concentration ([Ca2+]i), and apoptosis resistance. However, it is controversial which InsP3R isoforms mediate these effects and whether reduced ER [Ca2+] or enhanced [Ca2+]i signaling is most relevant for apoptosis protection. DT40 cell lines engineered to express each of the three mammalian InsP3R isoforms individually displayed enhanced apoptosis sensitivity compared with cells lacking InsP3R. In contrast, coexpression of each isoform with Bcl-xL conferred enhanced apoptosis resistance. In single-channel recordings of channel gating in native ER membranes, Bcl-xL increased the apparent sensitivity of all three InsP3R isoforms to subsaturating levels of InsP3. Expression of Bcl-xL reduced ER [Ca2+] in type 3 but not type 1 or 2 InsP3R-expressing cells. In contrast, Bcl-xL enhanced spontaneous [Ca2+]i signaling in all three InsP3R isoform-expressing cell lines. These results demonstrate a redundancy among InsP3R isoforms in their ability to sensitize cells to apoptotic insults and to interact with Bcl-xL to modulate their activities that result in enhanced apoptosis resistance. Furthermore, these data suggest that modulation of ER [Ca2+] is not a specific requirement for ER-dependent antiapoptotic effects of Bcl-xL. Rather, apoptosis protection is conferred by enhanced spontaneous [Ca2+]i signaling by Bcl-xL interaction with all isoforms of the InsP3R.
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Inositol Trisphosphate Receptor ca2 release channels
Physical Review, 2007Co-Authors: Kevi J Foske, Carl White, Kingho Cheung, Donon Daniel MakAbstract:The Inositol 1,4,5-Trisphosphate (InsP3) Receptors (InsP3Rs) are a family of Ca2+ release channels localized predominately in the endoplasmic reticulum of all cell types. They function to release Ca2+ into the cytoplasm in response to InsP3 produced by diverse stimuli, generating complex local and global Ca2+ signals that regulate numerous cell physiological processes ranging from gene transcription to secretion to learning and memory. The InsP3R is a calcium-selective cation channel whose gating is regulated not only by InsP3, but by other ligands as well, in particular cytoplasmic Ca2+. Over the last decade, detailed quantitative studies of InsP3R channel function and its regulation by ligands and interacting proteins have provided new insights into a remarkable richness of channel regulation and of the structural aspects that underlie signal transduction and permeation. Here, we focus on these developments and review and synthesize the literature regarding the structure and single-channel properties of the InsP3R.
Lihua He - One of the best experts on this subject based on the ideXlab platform.
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astrocyte Inositol triphosphate Receptor type 2 and cytosolic phospholipase a2 alpha regulate arteriole responses in mouse neocortical brain slices
PLOS ONE, 2012Co-Authors: Lihua He, David J Linden, Adam SapirsteinAbstract:Functional hyperemia of the cerebral vascular system matches regional blood flow to the metabolic demands of the brain. One current model of neurovascular control holds that glutamate released by neurons activates group I metabotropic glutamate Receptors (mGluRs) on astrocytes, resulting in the production of diffusible messengers that act to regulate smooth muscle cells surrounding cerebral arterioles. The acute mouse brain slice is an experimental system in which changes in arteriole diameter can precisely measured with light microscopy. Stimulation of the brain slice triggers specific cellular responses that can be correlated to changes in arteriole diameter. Here we used Inositol Trisphosphate Receptor type 2 (IP3R2) and cytosolic phospholipase A2 alpha (cPLA2α) deficient mice to determine if astrocyte mGluR activation coupled to IP3R2-mediated Ca2+ release and subsequent cPLA2α activation is required for arteriole regulation. We measured changes in astrocyte cytosolic free Ca2+ and arteriole diameters in response to mGluR agonist or electrical field stimulation in acute neocortical mouse brain slices maintained in 95% or 20% O2. Astrocyte Ca2+ and arteriole responses to mGluR activation were absent in IP3R2−/− slices. Astrocyte Ca2+ responses to mGluR activation were unchanged by deletion of cPLA2α but arteriole responses to either mGluR agonist or electrical stimulation were ablated. The valence of changes in arteriole diameter (dilation/constriction) was dependent upon both stimulus and O2 concentration. Neuron-derived NO and activation of the group I mGluRs are required for responses to electrical stimulation. These findings indicate that an mGluR/IP3R2/cPLA2α signaling cascade in astrocytes is required to transduce neuronal glutamate release into arteriole responses.