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Weidner P, Saar D, Söhn M, Schroeder T, Yu Y, Zöllner FG, Ponelies N, Zhou X, Zwicky A, Rohrbacher FN, Pattabiraman VR, Tanriver M, Bauer A, Ahmed H, Ametamey SM, Riffel P, Seger R, Bode JW, Wade RC, Ebert MPA, Kragelund BB, Burgermeister E. Myotubularin-related-protein-7 inhibits mutant (G12V) K-RAS by direct interaction. Cancer Lett 2024; 588:216783. [PMID: 38462034 DOI: 10.1016/j.canlet.2024.216783] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2023] [Revised: 02/19/2024] [Accepted: 03/03/2024] [Indexed: 03/12/2024]
Abstract
Inhibition of K-RAS effectors like B-RAF or MEK1/2 is accompanied by treatment resistance in cancer patients via re-activation of PI3K and Wnt signaling. We hypothesized that myotubularin-related-protein-7 (MTMR7), which inhibits PI3K and ERK1/2 signaling downstream of RAS, directly targets RAS and thereby prevents resistance. Using cell and structural biology combined with animal studies, we show that MTMR7 binds and inhibits RAS at cellular membranes. Overexpression of MTMR7 reduced RAS GTPase activities and protein levels, ERK1/2 phosphorylation, c-FOS transcription and cancer cell proliferation in vitro. We located the RAS-inhibitory activity of MTMR7 to its charged coiled coil (CC) region and demonstrate direct interaction with the gastrointestinal cancer-relevant K-RASG12V mutant, favouring its GDP-bound state. In mouse models of gastric and intestinal cancer, a cell-permeable MTMR7-CC mimicry peptide decreased tumour growth, Ki67 proliferation index and ERK1/2 nuclear positivity. Thus, MTMR7 mimicry peptide(s) could provide a novel strategy for targeting mutant K-RAS in cancers.
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Affiliation(s)
- Philip Weidner
- Department of Medicine II, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
| | - Daniel Saar
- Structural Biology and NMR Laboratory (SBiNLab) and the Linderstrøm-Lang Centre for Protein Science, Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Michaela Söhn
- Department of Medicine II, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
| | - Torsten Schroeder
- Department of Medicine II, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
| | - Yanxiong Yu
- Department of Medicine II, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
| | - Frank G Zöllner
- Computer Assisted Clinical Medicine, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany; Mannheim Institute for Intelligent Systems in Medicine, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany; Cooperative Core Facility Animal Scanner ZI, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
| | - Norbert Ponelies
- Orthopaedics & Trauma Surgery, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
| | - Xiaobo Zhou
- Department of Medicine I, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
| | - André Zwicky
- Laboratory of Organic Chemistry, Department of Chemistry and Applied Bioscience of ETH, Zurich, Switzerland
| | - Florian N Rohrbacher
- Laboratory of Organic Chemistry, Department of Chemistry and Applied Bioscience of ETH, Zurich, Switzerland
| | - Vijaya R Pattabiraman
- Laboratory of Organic Chemistry, Department of Chemistry and Applied Bioscience of ETH, Zurich, Switzerland
| | - Matthias Tanriver
- Laboratory of Organic Chemistry, Department of Chemistry and Applied Bioscience of ETH, Zurich, Switzerland
| | - Alexander Bauer
- Structural Biology and NMR Laboratory (SBiNLab) and the Linderstrøm-Lang Centre for Protein Science, Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Hazem Ahmed
- Institute of Pharmaceutical Sciences, Department of Chemistry and Applied Biosciences of ETH, Zurich, Switzerland
| | - Simon M Ametamey
- Institute of Pharmaceutical Sciences, Department of Chemistry and Applied Biosciences of ETH, Zurich, Switzerland
| | - Philipp Riffel
- Clinic of Radiology and Nuclear Medicine, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
| | - Rony Seger
- Department of Immunology and Regenerative Biology, Weizmann Institute of Science, Rehovot, Israel
| | - Jeffrey W Bode
- Laboratory of Organic Chemistry, Department of Chemistry and Applied Bioscience of ETH, Zurich, Switzerland
| | - Rebecca C Wade
- Heidelberg Institute for Theoretical Studies (HITS), Heidelberg, Germany; Heidelberg University, Zentrum für Molekulare Biologie (ZMBH), DKFZ-ZMBH Alliance, and Interdisciplinary Center for Scientific Computing (IWR), Heidelberg, Germany
| | - Matthias P A Ebert
- Department of Medicine II, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany; DKFZ-Hector Institute at the University Medical Center, Mannheim, Germany
| | - Birthe B Kragelund
- Structural Biology and NMR Laboratory (SBiNLab) and the Linderstrøm-Lang Centre for Protein Science, Department of Biology, University of Copenhagen, Copenhagen, Denmark.
| | - Elke Burgermeister
- Department of Medicine II, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany.
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Ardenkjær-Skinnerup J, Saar D, Petersen PSS, Pedersen M, Svingen T, Kragelund BB, Hadrup N, Ravn-Haren G, Emanuelli B, Brown KA, Vogel U. PPARγ antagonists induce aromatase transcription in adipose tissue cultures. Biochem Pharmacol 2024; 222:116095. [PMID: 38423186 DOI: 10.1016/j.bcp.2024.116095] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Revised: 01/11/2024] [Accepted: 02/26/2024] [Indexed: 03/02/2024]
Abstract
Aromatase is the rate-limiting enzyme in the biosynthesis of estrogens and a key risk factor for hormone receptor-positive breast cancer. In postmenopausal women, estrogens synthesized in adipose tissue promotes the growth of estrogen receptor positive breast cancers. Activation of peroxisome proliferator-activated receptor gamma (PPARγ) in adipose stromal cells (ASCs) leads to decreased expression of aromatase and differentiation of ASCs into adipocytes. Environmental chemicals can act as antagonists of PPARγ and disrupt its function. This study aimed to test the hypothesis that PPARγ antagonists can promote breast cancer by stimulating aromatase expression in human adipose tissue. Primary cells and explants from human adipose tissue as well as A41hWAT, C3H10T1/2, and H295R cell lines were used to investigate PPARγ antagonist-stimulated effects on adipogenesis, aromatase expression, and estrogen biosynthesis. Selected antagonists inhibited adipocyte differentiation, preventing the adipogenesis-associated downregulation of aromatase. NMR spectroscopy confirmed direct interaction between the potent antagonist DEHPA and PPARγ, inhibiting agonist binding. Short-term exposure of ASCs to PPARγ antagonists upregulated aromatase only in differentiated cells, and a similar effect could be observed in human breast adipose tissue explants. Overexpression of PPARG with or without agonist treatment reduced aromatase expression in ASCs. The data suggest that environmental PPARγ antagonists regulate aromatase expression in adipose tissue through two mechanisms. The first is indirect and involves inhibition of adipogenesis, while the second occurs more acutely.
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Affiliation(s)
- Jacob Ardenkjær-Skinnerup
- The National Food Institute, Technical University of Denmark, Kongens Lyngby, Denmark; The National Research Centre for the Working Environment, Copenhagen Ø, Denmark
| | - Daniel Saar
- REPIN and Structural Biology and NMR Laboratory, Department of Biology, University of Copenhagen, Copenhagen N, Denmark
| | - Patricia S S Petersen
- The Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, Copenhagen N, Denmark
| | - Mikael Pedersen
- The National Food Institute, Technical University of Denmark, Kongens Lyngby, Denmark
| | - Terje Svingen
- The National Food Institute, Technical University of Denmark, Kongens Lyngby, Denmark
| | - Birthe B Kragelund
- REPIN and Structural Biology and NMR Laboratory, Department of Biology, University of Copenhagen, Copenhagen N, Denmark
| | - Niels Hadrup
- The National Food Institute, Technical University of Denmark, Kongens Lyngby, Denmark; The National Research Centre for the Working Environment, Copenhagen Ø, Denmark
| | - Gitte Ravn-Haren
- The National Food Institute, Technical University of Denmark, Kongens Lyngby, Denmark
| | - Brice Emanuelli
- The Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, Copenhagen N, Denmark
| | - Kristy A Brown
- Department of Medicine, Weill Cornell Medicine, New York, NY, USA; Department of Cell Biology and Physiology, University of Kansas Medical Center, Kansas City, KS, USA.
| | - Ulla Vogel
- The National Food Institute, Technical University of Denmark, Kongens Lyngby, Denmark; The National Research Centre for the Working Environment, Copenhagen Ø, Denmark.
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McDowell MA, Heimes M, Enkavi G, Farkas Á, Saar D, Wild K, Schwappach B, Vattulainen I, Sinning I. The GET insertase exhibits conformational plasticity and induces membrane thinning. Nat Commun 2023; 14:7355. [PMID: 37963916 PMCID: PMC10646013 DOI: 10.1038/s41467-023-42867-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2023] [Accepted: 10/24/2023] [Indexed: 11/16/2023] Open
Abstract
The eukaryotic guided entry of tail-anchored proteins (GET) pathway mediates the biogenesis of tail-anchored (TA) membrane proteins at the endoplasmic reticulum. In the cytosol, the Get3 chaperone captures the TA protein substrate and delivers it to the Get1/Get2 membrane protein complex (GET insertase), which then inserts the substrate via a membrane-embedded hydrophilic groove. Here, we present structures, atomistic simulations and functional data of human and Chaetomium thermophilum Get1/Get2/Get3. The core fold of the GET insertase is conserved throughout eukaryotes, whilst thinning of the lipid bilayer occurs in the vicinity of the hydrophilic groove to presumably lower the energetic barrier of membrane insertion. We show that the gating interaction between Get2 helix α3' and Get3 drives conformational changes in both Get3 and the Get1/Get2 membrane heterotetramer. Thus, we provide a framework to understand the conformational plasticity of the GET insertase and how it remodels its membrane environment to promote substrate insertion.
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Affiliation(s)
- Melanie A McDowell
- Heidelberg University Biochemistry Center (BZH), Im Neuenheimer Feld 328, 69120, Heidelberg, Germany.
- Max Planck Institute of Biophysics, Max-von-Laue Strasse 3, 60438, Frankfurt am Main, Germany.
| | - Michael Heimes
- Heidelberg University Biochemistry Center (BZH), Im Neuenheimer Feld 328, 69120, Heidelberg, Germany
| | - Giray Enkavi
- Department of Physics, University of Helsinki, P. O. Box 64, FI-00014, Helsinki, Finland
| | - Ákos Farkas
- Department of Molecular Biology, University Medical Center Göttingen, 37073, Göttingen, Germany
| | - Daniel Saar
- Heidelberg University Biochemistry Center (BZH), Im Neuenheimer Feld 328, 69120, Heidelberg, Germany
| | - Klemens Wild
- Heidelberg University Biochemistry Center (BZH), Im Neuenheimer Feld 328, 69120, Heidelberg, Germany
| | - Blanche Schwappach
- Department of Molecular Biology, University Medical Center Göttingen, 37073, Göttingen, Germany
| | - Ilpo Vattulainen
- Department of Physics, University of Helsinki, P. O. Box 64, FI-00014, Helsinki, Finland
| | - Irmgard Sinning
- Heidelberg University Biochemistry Center (BZH), Im Neuenheimer Feld 328, 69120, Heidelberg, Germany.
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Martinsen JH, Saar D, Fernandes CB, Schuler B, Bugge K, Kragelund BB. Structure, Dynamics and Stability of the Globular Domain of Human Linker Histone H1.0 and the Role of Positive Charges. Protein Sci 2022; 31:918-932. [PMID: 35066947 PMCID: PMC8927875 DOI: 10.1002/pro.4281] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2021] [Revised: 01/14/2022] [Accepted: 01/20/2022] [Indexed: 11/25/2022]
Abstract
Linker histone H1 (H1) is an abundant chromatin‐binding protein that acts as an epigenetic regulator binding to nucleosomes and altering chromatin structures and dynamics. Nonetheless, the mechanistic details of its function remain poorly understood. Recent work suggest that the number and position of charged side chains on the globular domain (GD) of H1 influence chromatin structure and hence gene repression. Here, we solved the solution structure of the unbound GD of human H1.0, revealing that the structure is almost completely unperturbed by complex formation, except for a loop connecting two antiparallel β‐strands. We further quantified the role of the many positive charges of the GD for its structure and conformational stability through the analysis of 11 charge variants. We find that modulating the number of charges has little effect on the structure, but the stability is affected, resulting in a difference in melting temperature of 26 K between GD of net charge +5 versus +13. This result suggests that the large number of positive charges on H1‐GDs have evolved for function rather than structure and high stability. The stabilization of the GD upon binding to DNA can thus be expected to have a pronounced electrostatic component, a contribution that is amenable to modulation by posttranslational modifications, especially acetylation and phosphorylation. PDB Code(s): 6hq1;
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Affiliation(s)
- Jacob H Martinsen
- REPIN and the Structural Biology and NMR Laboratory, The Linderstrøm-Lang Centre for Protein Science, Department of Biology, University of Copenhagen, Copenhagen, Ole Maaloes Vej 5, DK-.2200, Copenhagen N, Denmark
| | - Daniel Saar
- REPIN and the Structural Biology and NMR Laboratory, The Linderstrøm-Lang Centre for Protein Science, Department of Biology, University of Copenhagen, Copenhagen, Ole Maaloes Vej 5, DK-.2200, Copenhagen N, Denmark
| | - Catarina B Fernandes
- REPIN and the Structural Biology and NMR Laboratory, The Linderstrøm-Lang Centre for Protein Science, Department of Biology, University of Copenhagen, Copenhagen, Ole Maaloes Vej 5, DK-.2200, Copenhagen N, Denmark
| | - Benjamin Schuler
- Department of Biochemistry, University of Zurich, Zurich, Switzerland.,Department of Physics, Winterthurerstrasse 190, 8057 University of Zurich, Zurich, Switzerland
| | - Katrine Bugge
- REPIN and the Structural Biology and NMR Laboratory, The Linderstrøm-Lang Centre for Protein Science, Department of Biology, University of Copenhagen, Copenhagen, Ole Maaloes Vej 5, DK-.2200, Copenhagen N, Denmark
| | - Birthe B Kragelund
- REPIN and the Structural Biology and NMR Laboratory, The Linderstrøm-Lang Centre for Protein Science, Department of Biology, University of Copenhagen, Copenhagen, Ole Maaloes Vej 5, DK-.2200, Copenhagen N, Denmark
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Almeyda CV, Eid SG, Saar D, Samuitiene M, Pappu HR. Comparative analysis of endogenous plant pararetroviruses in cultivated and wild Dahlia spp. Virus Genes 2013; 48:140-52. [PMID: 24353027 DOI: 10.1007/s11262-013-0997-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2013] [Accepted: 10/16/2013] [Indexed: 11/28/2022]
Abstract
Two distinct caulimoviruses, Dahlia mosaic virus (DMV) and Dahlia common mosaic virus, and an endogenous plant pararetroviral sequence (DvEPRS) were reported in Dahlia spp. DvEPRS, previously referred to as DMV-D10, was originally identified in the US from the cultivated Dahlia variabilis, and has also been found in New Zealand, Lithuania and Egypt, as well as in wild dahlia species growing in their natural habitats in Mexico. Sequence analysis of three new EPRSs from cultivated dahlias from Lithuania [D10-LT; 7,159 nucleotide level (nt)], New Zealand (D10-NZ, 7,156 nt), and the wild species, Dahlia rupicola, from Mexico (D10-DR, 7,133 nt) is reported in this study. The three EPRSs have the structure and organization typical of a caulimovirus species and showed identities among various open reading frames (ORFs) ranging between 71 and 97 % at the nt when compared to those or the known DvEPRS from the US. Examination of a dataset of seven full-length EPRSs obtained to date from cultivated and wild Dahlia spp. provided clues into genetic diversity of these EPRSs from diverse sources of dahlia. Phylogenetic analyses, mutation frequencies, potential recombination events, selection, and fitness were evaluated as evolutionary evidences for genetic variation. Assessment of all ORFs using phylogenomic and population genetics approaches suggests a wide genetic diversity of EPRSs occurring in dahlias. Phylogenetic analyses show that the EPRSs from various sources form one clade indicating a lack of clustering by geographical origin. Grouping of various EPRSs into two host taxa (cultivated vs. wild) shows little divergence with respect to their origin. Population genetic parameters demonstrate negative selection for all ORFs, with the reverse transcriptase region more variable than other ORFs. Recombination events were found which provide evolutionary evidence for genetic diversity among dahlia-associated EPRSs. This study contributes to an increased understanding of molecular population genetics and evolutionary pathways of these reverse transcribing viral elements.
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Affiliation(s)
- C V Almeyda
- Department of Plant Pathology, Washington State University, Pullman, WA, 99164, USA
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Saar D, Brauner J, Farber H, Petrucci S. Dielectric relaxation of some 1:1 electrolytes in tetrahydrofuran and diethyl carbonate. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100506a018] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Abstract
This review describes research that combines cellular physiology with behavioral neuroscience, to study the cellular mechanisms underlying learning and memory in the mammalian brain. Rats were trained with an olfactory conditioning paradigm, in which they had to memorize odors in order to be rewarded with drinking water. Such training results in rule learning, which enables enhanced acquisition of odor memory. Training results in the following learning-related physiological modifications in intrinsic and synaptic properties in olfactory (piriform) cortex pyramidal neurons: 1. increased neuronal excitability, indicated by reduced afterhyperpolarization, and 2. increased synaptic transmission, indicated by reduced paired-pulse facilitation. These modifications are correlated to enhanced learning capability rather than to storage of memory for specific odors. In addition, using a different paradigm of odor-training, it is shown that NMDA and betra-adrenergic receptors are involved at different stages of long-term memory consolidation.
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Affiliation(s)
- E Barkai
- Department of Morphology, Faculty of Health Sciences and Zlotowski Center for Neuroscience, Ben-Gurion University of the Negev, Beer-Sheva, Israel.
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Saar D, Grossman Y, Barkai E. Long-lasting cholinergic modulation underlies rule learning in rats. J Neurosci 2001; 21:1385-92. [PMID: 11160410 PMCID: PMC6762243] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/18/2023] Open
Abstract
We studied the role of acetylcholine (ACh) in creating learning-related long-lasting modifications in the rat cortex. Rats were trained to discriminate positive and negative cues in pairs of odors, until they demonstrated rule learning and entered a mode of high capability for learning of additional odors. We have previously reported that pyramidal neurons in olfactory (piriform) cortex from trained rats had reduced spike afterhyperpolarization (AHP) for 3 d after rule learning. In the present study we examined the mechanism underlying this long-lasting modification. The cholinergic agonist carbachol reduced both slow AHP and firing adaptation in neurons from pseudotrained rats, but had no effect on neurons from trained rats, suggesting pre-existing cholinergic effect. Intracellular application of the calcium chelator BAPTA abolished the difference in slow AHP and in adaptation between groups, suggesting that the difference resulted from reduction in the ACh-sensitive, Ca(2+)-dependent potassium current, I(AHP). At the behavioral level, application of the muscarinic blocker scopolamine before each training session delayed rule learning but had no effect on further acquisition of odor memory. We suggest that intense ACh activity during rule learning enhances neuronal excitability in the piriform cortex by reducing I(AHP) and that the effect outlasts the stage of rule learning, so that ACh activity is not crucial for further odor learning.
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Affiliation(s)
- D Saar
- Departments of Physiology and Morphology, Faculty of Health Sciences and Zlotowski Center for Neuroscience, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel
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Saar D, Grossman Y, Barkai E. Reduced synaptic facilitation between pyramidal neurons in the piriform cortex after odor learning. J Neurosci 1999; 19:8616-22. [PMID: 10493761 PMCID: PMC6783041] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/1999] [Revised: 07/14/1999] [Accepted: 07/14/1999] [Indexed: 02/14/2023] Open
Abstract
Learning-related cellular modifications were studied in the rat piriform cortex after operand conditioning. Rats were trained to discriminate positive cues in pairs of odors. In one experimental paradigm, rats were trained to memorize 35-50 pairs of odors ("extensive training"). In another paradigm, training was continued only until rats acquired the rule of the task, usually after learning the first two pairs of odors ("short training"). "Pseudotrained" and "naive" rats served as controls. We have previously shown that "rule learning" of this task was accompanied by reduced spike afterhyperpolarization in pyramidal neurons in brain slices of the piriform cortex. In the present study, synaptic inputs to the same cells were examined. Pairs of electrical stimuli applied to the intrinsic fibers that interconnect layer II pyramidal neurons revealed significant reduction in paired-pulse facilitation (PPF) in this pathway even after short training. PPF in shortly trained rats was reduced to the same extent as in extensively trained rats. PPF reduction did not result from modification of membrane properties in the postsynaptic cells, change in postsynaptic inhibition, or impairment of the facilitation mechanism. Extracellular field potential recordings showed enhanced synaptic transmission in these synapses. The reduction in PPF became apparent only 3 d after task acquisition and returned to control value 5 d later. PPF evoked by stimulating the afferent fibers to the same neurons was increased 1 d after training for 2 d. We suggest that the transient enhancement in connectivity in the intrinsic pathway is related to the enhanced learning capability and not to memory for specific odors, which lasts for weeks.
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Affiliation(s)
- D Saar
- Department of Physiology, Faculty of Health Sciences and Zlotowski Center for Neuroscience, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel
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Saar D, Grossman Y, Barkai E. Reduced after-hyperpolarization in rat piriform cortex pyramidal neurons is associated with increased learning capability during operant conditioning. Eur J Neurosci 1998; 10:1518-23. [PMID: 9749805 DOI: 10.1046/j.1460-9568.1998.00149.x] [Citation(s) in RCA: 169] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Learning-related cellular modifications were studied in the rat piriform cortex. Water-deprived rats were divided to three groups: 'trained' rats were trained in a four-arm maze to discriminate positive cues in pairs of odours, 'control' rats were 'pseudo-trained' by random water rewarding, and 'naive' rats were water-deprived only. In one experimental paradigm, the trained group was exposed to extensive training with rats learning to discriminate between 35 and 50 pairs of odours. Piriform cortex pyramidal neurons from 'trained', 'control' and 'naive' rats did not differ in their passive membrane properties and single spike characteristics. However, the after-hyperpolarizations (AHPs) that follow six-spike trains were reduced after 'extensive training' by 43% and 36% compared with 'control' and 'naive', respectively. This effect was not observed in the piriform cortex of another group of rats, in which hyperexcitability was induced by chemical kindling. In another experimental paradigm rats were trained only until they demonstrated 'rule learning', usually after discriminating between one and two pairs of odours ('mild training'). In this experiment, a smaller, yet significant, reduction (20%) in AHPs was observed. AHP reduction was apparent in most of the sampled neurons. AHP remained reduced up to 3 days after the last training session. 5 days or more after the last training session, AHP amplitude recovered to pre-training value and did not differ between 'trained' rats and the others. Accordingly, training suspension for 5 days or more resulted in slower learning of novel odours. We suggest that increased neuronal excitability, manifested as reduced AHP, is related to the ability of the cortical network to enter a 'learning mode' which creates favourable conditions for enhanced learning capability.
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Affiliation(s)
- D Saar
- Department of Physiology, Faculty of Health Sciences and Zlotowski Center for Neuroscience, Ben-Gurion University of the Negev, Beer-Sheva, Israel
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Saar D, Lebel D, Grossman Y, Barkai E. Transient synaptic modifications in piriform cortex pyramidal cells associated with odor learning. Neurosci Lett 1997. [DOI: 10.1016/s0304-3940(97)90176-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Saar D, Grossman Y, Barkai E. Odor discrimination learning is correlated with reduced after-hyperpolarization in piriform cortex pyramidal cells. Neurosci Lett 1997. [DOI: 10.1016/s0304-3940(97)90175-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Yuste R, Gutnick MJ, Saar D, Delaney KR, Tank DW. Ca2+ accumulations in dendrites of neocortical pyramidal neurons: an apical band and evidence for two functional compartments. Neuron 1994; 13:23-43. [PMID: 8043278 DOI: 10.1016/0896-6273(94)90457-x] [Citation(s) in RCA: 241] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Apical dendrites constitute a prominent feature of the microcircuitry in the neocortex, yet their function is poorly understood. Using fura-2 imaging of layer 5 pyramidal neurons from slices of rat somatosensory cortex, we have investigated the Ca2+ influx into dendrites under intracellular, antidromic, synaptic, and receptor-agonist stimulation. We find three spatial patterns of Ca2+ accumulations: an apical band in the apical dendrite approximately 500 microns from the soma, an accumulation restricted to the basal dendrites, soma, and proximal apical dendrite, and a combination of both of these. We show that the apical band can be activated antidromically and synaptically and that, under blocked Na+ and K+ conductances, it generates Ca2+ spikes. Thus, the apical band may serve as a dendritic trigger zone for regenerative Ca2+ spikes or as a current amplifier for distal synaptic events. Our results suggest that the distal apical dendrite should be considered a separate functional compartment from the rest of the cell.
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Affiliation(s)
- R Yuste
- Biological Computation Research Department, AT&T Bell Laboratories, Murray Hill, New Jersey 07974
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Abstract
This study compared changes in movement velocity, force, and work from bilateral quadriceps muscle stimulation during resistive squatting exercise to identical exercise without stimulation. Both the group undergoing resistive training over 24 sessions (N = 9) and the group receiving the same treatment in conjunction with stimulation during the last 12 sessions (N = 9) showed significant improvements in measures of movement velocity, force, total work, power, sprint time, and vertical jump distance when compared to a control group receiving no treatment (N = 9). All subjects were baseline tested and tested at 3, 6, and 7 week intervals. Both experimental groups improved significantly for all measures, but the electrical stimulation group did not produce more significant changes overall than those with resistive training alone. However, when compared to control measures, the effect of electrical stimulation-augmented responses among some measures was more pronounced than the effect of resistive training alone.
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Ariel GB, Saar D, Selinger A, Penny MA, Saar I. COMPUTERIZED FORMATION ANALYSIS FOR TEAM EVENTS. Med Sci Sports Exerc 1983. [DOI: 10.1249/00005768-198315020-00118] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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