Medical Sciences Commons^™

Effects Of Hypothyroidism On Cell Proliferation And Neuroblasts In The Hippocampal Dentate Gyrus In A Rat Model Of Type 2 Diabetes, Sun Shin Yi, In Koo Hwang, Ji Won Choi, Moo-Ho Won, Je Kyung Seong, Yeo Sung Yoon

Biomedical Sciences Faculty Research and Publications

We observed how the hypothyroid state affects diabetic states and modifies cell proliferation and neuroblast differentiation in the hippocampal dentate gyrus (DG). For this, 0.03% methimazole, an anti-thyroid drug, was administered to 7-week-old, pre-diabetic Zucker diabetic fatty (ZDF) rats by drinking water for 5 weeks, and the animals were sacrificed at 12 weeks of age. At this age, corticosterone levels were significantly increased in the ZDF rats compared to those in the control (Zucker lean control, ZLC) rats. Methimazole (methi) treatment in the ZDF rats (ZDF-methi rats) significantly decreased corticosterone levels and diabetes-induced hypertrophy of adrenal glands. In the DG, …

Molecular Requirements For Ethanol Differential Allosteric Modulation Of Ligand-Gated Ion Channels Based On Selective Gβγ Modulation, Gonzalo E. Yevenes, Gustavo Moraga-Cid, Ariel Avila, Leonardo Guzman, Maximiliano Figueroa, Robert W. Peoples, Luis G. Aguayo

Biomedical Sciences Faculty Research and Publications

It is now believed that the allosteric modulation produced by ethanol in glycine receptors (GlyRs) depends on alcohol binding to discrete sites within the protein structure. Thus, the differential ethanol sensitivity of diverse GlyR isoforms and mutants was explained by the presence of specific residues in putative alcohol pockets. Here, we demonstrate that ethanol sensitivity in two LGIC members, the GlyR adult α₁ and embryonic α₂ subunits, can be modified through selective mutations that rescued or impaired Gβγ modulation. Even though that both isoforms were able to physically interact with Gβγ, only the α₁ GlyR was functionally …

Transcriptional Profiles For Glutamate Transporters Reveal Differences Between Organophosphates But Similarities With Unrelated Neurotoxicants, Theodore A. Slotkin, Doug Lobner, Frederic J. Seidler

Biomedical Sciences Faculty Research and Publications

The developmental neurotoxicity of organophosphates involves mechanisms other than their shared property as cholinesterase inhibitors, among which are excitotoxicity and oxidative stress. We used PC12 cells as a neurodevelopmental model to compare the effects of chlorpyrifos and diazinon on the expression of genes encoding glutamate transporters. Chlorpyrifos had a greater effect in cells undergoing nerve growth factor-induced neurodifferentiation as compared to undifferentiated PC12 cells, with peak sensitivity at the initiation of differentiation, reflecting a global upregulation of all the glutamate transporter genes expressed in this cell line. In differentiating cells, chlorpyrifos had a significantly greater effect than did diazinon and …

Involvement Of Noradrenergic Neurotransmission In The Stress- But Not Cocaine-Induced Reinstatement Of Extinguished Cocaine-Induced Conditioned Place Preference In Mice: Role For Β-2 Adrenergic Receptors, John R. Mantsch, Andy Meyer, Oliver Vranjkovic, Chad E. Beyer, David A. Baker, Holly Caretta

Biomedical Sciences Faculty Research and Publications

The responsiveness of central noradrenergic systems to stressors and cocaine poses norepinephrine as a potential common mechanism through which drug re-exposure and stressful stimuli promote relapse. This study investigated the role of noradrenergic systems in the reinstatement of extinguished cocaine-induced conditioned place preference by cocaine and stress in male C57BL/6 mice. Cocaine- (15 mg/kg, i.p.) induced conditioned place preference was extinguished by repeated exposure to the apparatus in the absence of drug and reestablished by a cocaine challenge (15 mg/kg), exposure to a stressor (6-min forced swim (FS); 20–25°C water), or administration of the α-2 adrenergic receptor (AR) antagonists yohimbine …

Toxicity Of Flow Line, Durafill Vs, And Dycal To Dental Pulp Cells: Effects Of Growth Factors, Alyssa Furey, Julie Hjelmhaug, Doug Lobner

Biomedical Sciences Faculty Research and Publications

Introduction

The objective was to determine the effects of growth factor treatment on dental pulp cell sensitivity to toxicity of 2 composite restoration materials, Flow Line and Durafill VS, and a calcium hydroxide pulp capping material, Dycal.

Methods

Toxicity of the dental materials to cultures of primary dental pulp cells was determined by the MTT metabolism assay. The ability of 6 different growth factors to influence the toxicity was tested.

Results

A 24-hour exposure to either Flow Line or Durafill VS caused approximately 40% cell death, whereas Dycal exposure caused approximately 80% cell death. The toxicity of Flow Line and …

Synaptotoxicity Of Alzheimer Beta Amyloid Can Be Explained By Its Membrane Perforating Property, Fernando Sepulveda, Jorge Parodi, Robert W. Peoples, Carlos Opazo, Luis G. Aguayo

Biomedical Sciences Faculty Research and Publications

The mechanisms that induce Alzheimer’s disease (AD) are largely unknown thereby deterring the development of disease-modifying therapies. One working hypothesis of AD is that Aβ excess disrupts membranes causing pore formation leading to alterations in ionic homeostasis. However, it is largely unknown if this also occurs in native brain neuronal membranes. Here we show that similar to other pore forming toxins, Aβ induces perforation of neuronal membranes causing an increase in membrane conductance, intracellular calcium and ethidium bromide influx. These data reveal that the target of Aβ is not another membrane protein, but that Aβ itself is the cellular target …

Pathologically Activated Neuroprotection Via Uncompetitive Blockade Of N-Methyl-D-Aspartate Receptors With Fast Off-Rate By Novel Multifunctional Dimer Bis(Propyl)-Cognitin, Jialie Luo, Wenming Li, Yuming Zhao, Hongjun Fu, Dik-Lung Ma, Jing Tang, Chaoying Li, Robert W. Peoples, Fushun Li, Qinwen Wang, Pingbo Huang, Jun Xia, Yuanping Pang, Yifan Han

Biomedical Sciences Faculty Research and Publications

Uncompetitive N-methyl-d-aspartate (NMDA) receptor antagonists with fast off-rate (UFO) may represent promising drug candidates for various neurodegenerative disorders. In this study, we report that bis(propyl)-cognitin, a novel dimeric acetylcholinesterase inhibitor and γ-aminobutyric acid subtype A receptor antagonist, is such an antagonist of NMDA receptors. In cultured rat hippocampal neurons, we demonstrated that bis(propyl)-cognitin voltage-dependently, selectively, and moderately inhibited NMDA-activated currents. The inhibitory effects of bis(propyl)-cognitin increased with the rise in NMDA and glycine concentrations. Kinetics analysis showed that the inhibition was of fast onset and offset with an off-rate time constant of 1.9 s. Molecular docking simulations showed moderate …

Drug-Induced Plasticity Contributing To Heightened Relapse Susceptibility: Neurochemical Changes And Augmented Reinstatement In High-Intake Rats, Aric Madayag, Kristen S. Kau, Doug Lobner, John R. Mantsch, Samantha Wisniewski, David A. Baker

Biomedical Sciences Faculty Research and Publications

A key in understanding the neurobiology of addiction and developing effective pharmacotherapies is revealing drug-induced plasticity that results in heightened relapse susceptibility. Previous studies have demonstrated that increased extracellular glutamate, but not dopamine, in the nucleus accumbens core (NAcc) is necessary for cocaine-induced reinstatement. In this report, we examined whether drug-induced adaptations that are necessary to generate cocaine-induced reinstatement also determine relapse vulnerability. To do this, rats were assigned to self-administer cocaine under conditions resulting in low (2 h/d; 0.5 mg/kg/infusion, i.v.) or high (6 h/d; 1.0 mg/kg/infusion, i.v.) levels of drug intake since these manipulations produce groups of rats …

Differential Actions Of Ethanol And Trichloroethanol At Sites In The M3 And M4 Domains Of The Nmda Receptor Glun2a (Nr2a) Subunit, Ak Salous, H Ren, Ka Lamb, Xiang-Qun Hu, Rh Lipsky, Robert W. Peoples

Biomedical Sciences Faculty Research and Publications

Background and purpose:  Alcohol produces its behavioural effects in part due to inhibition of N-methyl-d-aspartate (NMDA) receptors in the CNS. Previous studies have identified amino acid residues in membrane-associated domains 3 (M3) and 4 (M4) of the NMDA receptor that influence ethanol sensitivity. In addition, in other alcohol-sensitive ion channels, sedative-hypnotic agents have in some cases been shown to act at sites distinct from the sites of ethanol action. In this study, we compared the influence of mutations at these sites on sensitivity to ethanol and trichloroethanol, a sedative-hypnotic agent that is a structural analogue of ethanol.

Experimental approach: …

Neuroadaptations In The Cellular And Postsynaptic Group 1 Metabotropic Glutamate Receptor Mglur5 And Homer Proteins Following Extinction Of Cocaine Self-Administration, M. Behnam Ghasemzadeh, Preethi Vasudevan, Christopher Mueller, Chad Seubert, John R. Mantsch

Biomedical Sciences Faculty Research and Publications

This study examined the role of group1 metabotropic glutamate receptor mGluR5 and associated postsynaptic scaffolding protein Homer1b/c in behavioral plasticity after three withdrawal treatments from cocaine self-administration. Rats self-administered cocaine or saline for 14 days followed by a withdrawal period during which rats underwent extinction training, remained in their home cages, or were placed in the self-administration chambers in the absence of extinction. Subsequently, the tissue level and distribution of proteins in the synaptosomal fraction associated with the postsynaptic density were examined. Cocaine self-administration followed by home cage exposure reduced the mGluR5 protein in nucleus accumbens (NA) shell and dorsolateral …

A Selective Gβγ-Linked Intracellular Mechanism For Modulation Of A Ligand-Gated Ion Channel By Ethanol, Gonzalo E. Yevenes, Gustavo Moraga-Cid, Robert W. Peoples, Günther Schmalzing, Luis G. Aguayo

Biomedical Sciences Faculty Research and Publications

The current understanding about ethanol effects on the ligand-gated ion channel (LGIC) superfamily has been restricted to identify potential binding sites within transmembrane (TM) domains in the Cys-loop family. Here, we demonstrate a key role of the TM3–4 intracellular loop and Gβγ signaling for potentiation of glycine receptors (GlyRs) by ethanol. We discovered 2 motifs within the large intracellular loop of the GlyR α₁ subunit that are critical for the actions of pharmacological concentrations of ethanol. Significantly, the sites were ethanol-specific because they did not alter the sensitivity to general anesthetics, neurosteroids, or longer n-alcohols. Furthermore, Gβγ scavengers …

Evidence That Α2-Antiplasmin Becomes Covalently Ligated To Plasma Fibrinogen In The Circulation: A New Role For Plasma Factor Xiii In Fibrinolysis Regulation, Michael W. Mosesson, Kevin R. Siebenlist, Irene Hernandez, K. N. Lee, V. J. Christiansen, P. A. Mckee

Biomedical Sciences Faculty Research and Publications

Background:

Plasma alpha₂-antiplasmin (α₂AP) is a rapid and effective inhibitor of the fibrinolytic enzyme plasmin. Congenital α₂AP deficiency results in a severe hemorrhagic disorder due to accelerated fibrinolysis. It is well established that in the presence of thrombin-activated factor XIII (FXIIIa), α₂AP becomes covalently ligated to the distal α chains of fibrin or fibrinogen at lysine 303 (two potential sites per molecule). Some time ago we showed that α₂AP is covalently linked to plasma fibrinogen . That singular observation led to our hypothesis that native plasma factor XIII (FXIII), …

Blunted Cystine–Glutamate Antiporter Function In The Nucleus Accumbens Promotes Cocaine-Induced Drug Seeking, Kristen S. Kau, Aric Madayag, John R. Mantsch, Mark D. Grier, Omer Abdulhameed, David A. Baker

Biomedical Sciences Faculty Research and Publications

Repeated cocaine alters glutamate neurotransmission, in part, by reducing cystine–glutamate exchange via system x_c−, which maintains glutamate levels and receptor stimulation in the extrasynaptic compartment. In the present study, we undertook two approaches to determine the significance of plasticity involving system x_c−. First, we examined whether the cysteine prodrug N-acetylcysteine attenuates cocaine-primed reinstatement by targeting system x_c−. Rats were trained to self-administer cocaine (1 mg/kg/200 μl, i.v.) under extended access conditions (6 h/day). After extinction training, cocaine (10 mg/kg, i.p.) primed reinstatement was assessed in rats pretreated with N-acetylcysteine (0–60 mg/kg, i.p.) in the …

Functional Interactions Of Alcohol-Sensitive Sites In The N-Methyl-D-Aspartate Receptor M3 And M4 Domains, Hong Ren, Abdelghaffar K. Salous, Jaclyn M. Paul, Kaitlin A. Lamb, Donard S. Dwyer, Robert W. Peoples

Biomedical Sciences Faculty Research and Publications

The N-methyl-d-aspartate receptor is an important mediator of the behavioral effects of ethanol in the central nervous system. Previous studies have demonstrated sites in the third and fourth membrane-associated (M) domains of the N-methyl-d-aspartate receptor NR2A subunit that influence alcohol sensitivity and ion channel gating. We investigated whether two of these sites, Phe-637 in M3 and Met-823 in M4, interactively regulate the ethanol sensitivity of the receptor by testing dual substitution mutants at these positions. A majority of the mutations decreased steady-state glutamate EC₅₀ values and maximal steady-state to peak current ratios (I_ss/I …

Stressor- And Corticotropin Releasing Factor-Induced Reinstatement And Active Stress-Related Behavioral Responses Are Augmented Following Long-Access Cocaine Self-Administration By Rats, John R. Mantsch, David A. Baker, David M. Francis, Eric S. Katz, Michael A. Hoks, Joseph P. Serge

Biomedical Sciences Faculty Research and Publications

Rationale Stressful events during periods of drug abstinence likely contribute to relapse in cocaine-dependent individuals. Excessive cocaine use may increase susceptibility to stressor-induced relapse through alterations in brain corticotropin-releasing factor (CRF) responsiveness.

Objectives This study examined stressor- and CRF-induced cocaine seeking and other stress-related behaviors in rats with different histories of cocaine self-administration (SA).

Materials and methods Rats self-administered cocaine under short-access (ShA; 2 h daily) or long-access (LgA; 6 h daily) conditions for 14 days or were provided access to saline and were tested for reinstatement by a stressor (electric footshock), cocaine or an icv injection of CRF and …

Repeated N-Acetylcysteine Administration Alters Plasticity-Dependent Effects Of Cocaine, Aric Madayag, Doug Lobner, Kristen S. Kau, John R. Mantsch, Omer Abdulhameed, Matthew Hearing, Mark D. Grier, David A. Baker

Biomedical Sciences Faculty Research and Publications

Cocaine produces a persistent reduction in cystine–glutamate exchange via system x_c− in the nucleus accumbens that may contribute to pathological glutamate signaling linked to addiction. System x_c− influences glutamate neurotransmission by maintaining basal, extracellular glutamate in the nucleus accumbens, which, in turn, shapes synaptic activity by stimulating group II metabotropic glutamate autoreceptors. In the present study, we tested the hypothesis that a long-term reduction in system x_c− activity is part of the plasticity produced by repeated cocaine that results in the establishment of compulsive drug seeking. To test this, the cysteine prodrug N-acetylcysteine …

Augmented Hypothalamic Corticotrophin-Releasing Hormone Mrna And Corticosterone Responses To Stress In Adult Rats Exposed To Perinatal Hypoxia, Hershel Raff, Lauren Jacobson, William E. Cullinan

Biomedical Sciences Faculty Research and Publications

Stressful events before or just after parturition alter the subsequent phenotypical response to stress in a general process termed programming. Hypoxia during the period before and during parturition, and in the postnatal period, is one of the most common causes of perinatal distress, morbidity, and mortality. We have found that perinatal hypoxia (prenatal day 19 to postnatal day 14) augmented the corticosterone response to stress and increased basal corticotrophin-releasing hormone (CRH) mRNA levels in the parvocellular portion of the paraventricular nucleus (PVN) in 6-month-old rats. There was no effect on the levels of hypothalamic parvocellular PVN vasopressin mRNA, anterior pituitary …

Mutations At F637 In The Nmda Receptor Nr2a Subunit M3 Domain Influence Agonist Potency, Ion Channel Gating And Alcohol Action, H. Ren, Ak Salous, J. M. Paul, Rh Lipsky, Robert W. Peoples

Biomedical Sciences Faculty Research and Publications

Background and purpose:

NMDA receptors are important molecular targets of ethanol action in the CNS. Previous studies have identified a site in membrane-associated domain 3 (M3) of the NR1 subunit and two sites in M4 of the NR2A subunit that influence alcohol action; the sites in NR2A M4 also regulate ion channel gating. The purpose of this study was to determine whether mutations at the site in the NR2A subunit corresponding to the NR1 M3 site influence alcohol action and ion channel gating.

Experimental approach:

We investigated the effects of mutations at phenylalanine (F) 637 of the NR2A subunit using …

Restraint-Induced Corticosterone Secretion And Hypothalamic Crh Mrna Expression Are Augmented During Acute Withdrawal From Chronic Cocaine Administration, John R. Mantsch, Sarah Taves, Tayyiba Khan, Eric S. Katz, Tanveer Sajan, Lee C. Tang, William E. Cullinan, Dana R. Ziegler

Biomedical Sciences Faculty Research and Publications

Stress responses during cocaine withdrawal likely contribute to drug relapse and may be intensified as a consequence of prior cocaine use. The present study examined changes in stressor-induced activation of the hypothalamic–pituitary–adrenal (HPA) axis during acute withdrawal from chronic cocaine administration. Adult male Sprague–Dawley rats received daily administration of cocaine (30 mg/kg, i.p.) or saline for 14 days. Twenty-four hours after the last injection, rats in each group were sacrificed under stress-free conditions or following 30 min of immobilization. Plasma corticosterone (CORT) was measured in trunk-blood using radioimmunoassay, corticotropin-releasing hormone (CRH) mRNA levels in the paraventricularnucleus (PVN) of the hypothalamus …

Β-N-Methylamino-L-Alanine Enhances Neurotoxicity Through Multiple Mechanisms, Doug Lobner, Peachy Mae T. Piana, Abed K. Salous, Robert W. Peoples

Biomedical Sciences Faculty Research and Publications

The idea that the environmental toxin β-N-methylamino-l-alanine (BMAA) is involved in neurodegenerative diseases on Guam has risen and fallen over the years. The theory has gained greater interest with recent reports that BMAA is biomagnified, is widely distributed around the planet, and is present in the brains of Alzheimer's patients in Canada. We provide two important new findings. First, we show that BMAA at concentrations as low as 10 μM can potentiate neuronal injury induced by other insults. This is the first evidence that BMAA at concentrations below the mM range can enhance death of cortical neurons and …

Fibrinogen-Containing Y Chains; Is The Assay Measuring What Farrell's Group Expects?, Kevin R. Siebenlist

Biomedical Sciences Faculty Research and Publications

No abstract provided.

Studies On The Basis For The Properties Of Fibrin Produced From Fibrinogen-Containing Γ′ Chains, Kevin R. Siebenlist, Michael W. Mosesson, Irene Hernandez, Leslie A. Bush, Enrico Di Cera, John R. Shainoff, James P. Diorio, Laurie Stajanovic

Biomedical Sciences Faculty Research and Publications

Human fibrinogen 1 is homodimeric with respect to its γ chains (`γ_A-γ_A'), whereas fibrinogen 2 molecules each contain one γ_A (γ_A1-411V) and one γ' chain, which differ by containing a unique C-terminal sequence from γ'408 to 427L that binds thrombin and factor XIII. We investigated the structural and functional features of these fibrins and made several observations. First, thrombin-treated fibrinogen 2 produced finer, more branched clot networks than did fibrin 1. These known differences in network structure were attributable to delayed release of fibrinopeptide (FP) A from fibrinogen 2 by thrombin, which in …

Do Inhalation General Anesthetic Drugs Induce The Neuronal Release Of Endogenous Opioid Peptides?, Raymond M. Quock, Linda K. Vaughn

Biomedical Sciences Faculty Research and Publications

The antagonism of some effects of inhalation general anesthetic agents by naloxone suggests that there may be an opioid component to anesthetic action. There is evidence that this opioid action component is due to neuronal release of endogenous opioid peptides. The strongest evidence is provided by studies that monitor changes in the concentration of opioid peptides in the perfused brain following inhalation of the anesthetic. Indirect or circumstantial evidence also comes from studies of anesthetic effects on regional brain levels of opioid peptides, antagonism of selected anesthetic effects by antisera to opioid peptides and anesthetic-induced changes radioligand binding to opioid …

Evidence That Catalytically-Inactivated Thrombin Forms Dimers That Bridge Between Fibrin/Fibrinogen Fibers And Enhance Polymerization, Michael W. Mosesson, Irene Hernandez, Kevin R. Siebenlist

Biomedical Sciences Faculty Research and Publications

Phe-pro-arg-chloromethyl ketone-inhibited α-thrombin [FPRα-thr] retains its fibrinogen recognition site (exosite 1), augments fibrin/fibrinogen [fibrin(ogen)] polymerization, and increases the incorporation of fibrin into clots. There are two ‘low-affinity’ thrombin-binding sites in each central E domain of fibrin, plus a non-substrate ‘high affinity’ γ′ chain thrombin-binding site on heterodimeric ‘fibrin(ogen) 2’ molecules (γ_A,γ′). ‘Fibrin(ogen) 1’ (γ_A, γ_A) containing only low-affinity thrombin-binding sites, showed concentration-dependent FPRα-thr enhancement of polymerization, thus indicating that low-affinity sites are sufficient for enhancing polymerization. FPRγ-thr, whose exosite 1 is non-functional, did not enhance polymerization of either fibrin(ogen)s 1 or 2 and DNA aptamer …

Detection And Mapping Of Quantitative Trait Loci That Determine Responsiveness, Janet L. Mueller, E. A. Ellenberger, Linda K. Vaughn, John K. Belknap, Raymond M. Quock

Biomedical Sciences Faculty Research and Publications

Exposure to 70% N₂O evokes a robust antinociceptive effect in C57BL/6 (B6) but not in DBA/2 (D2) inbred mice. This study was conducted to identify quantitative trait loci (QTL) in the mouse genome that might determine responsiveness to N₂O. Offspring from the F₂ generation bred from B6 and D2 progenitors exhibited a broad range of responsiveness to N₂O antinociception as determined by the acetic acid-induced abdominal constriction test. QTL analysis was then used to dissect this continuous trait distribution into component loci, and to map them to broad chromosomal regions. To this end, …

The Structure And Biological Features Of Fibrinogen And Fibrin, Michael W. Mosesson, Kevin R. Siebenlist, David A. Meh

Biomedical Sciences Faculty Research and Publications

Fibrinogen and fibrin play important, overlapping roles in blood clotting, fibrinolysis, cellular and matrix interactions, inflammation, wound healing, and neoplasia. These events are regulated to a large extent by fibrin formation itself and by complementary interactions between specific binding sites on fibrin(ogen) and extrinsic molecules including proenzymes, clotting factors, enzyme inhibitors, and cell receptors. Fibrinogen is comprised of two sets of three polypeptide chains termed Aα, Bβ, and γ, that are joined by disulfide bridging within the N-terminal E domain. The molecules are elongated 45-nm structures consisting of two outer D domains, each connected to a central E domain by …

Increased Mrna Expression For The Α1 Subunit Of The GabaA Receptor Following Nitrous Oxide Exposure In Mice, Lisa M. Johanek, William E. Cullinan, Linda K. Vaughn

Biomedical Sciences Faculty Research and Publications

The mechanisms by which nitrous oxide (N₂O) produces physical dependence and withdrawal seizures are not well understood, but both N₂O and ethanol exert some of their effects via the GABA_A receptor and several lines of evidence indicate that withdrawal from N₂O and ethanol may be produced through similar mechanisms. Expression levels of mRNA transcripts encoding several GABA_A receptor subunits change with chronic ethanol exposure and, therefore, we hypothesized that N₂O exposure would produce changes in mRNA expression for the α₁ subunit. Male, Swiss–Webster mice, 10–12 weeks of age, were …

Position Of Γ-Chain Carboxy-Terminal Regions In Fibrinogen/Fibrin Cross-Linking Mixtures, Kevin R. Siebenlist, David A. Meh, Michael W. Mosesson

Biomedical Sciences Faculty Research and Publications

There are conflicting ideas regarding the location of the carboxyl-terminal regions of cross-linked γ-chain dimers in double-stranded fibrin fibrils. Some investigators believe that the chains are always oriented longitudinally along each fibril strand and traverse the contacting ends of abutting fibrin D domains (“DD-long” cross-linking). Other investigations have indicated instead that the chains are situated transversely between adjacent D domains in opposing fibril strands (transverse cross-linking). To distinguish between these two possibilities, the γ dimer composition of factor XIIIa-cross-linked fibrin/fibrinogen complexes that had been formed through noncovalent D/E interactions between fibrinogen D domains and fibrin E domains was examined. Two …

The Location Of The Carboxy-Terminal Region Of Γ Chains In Fibrinogen And Fibrin D Domains, Michael W. Mosesson, Kevin R. Siebenlist, David A. Meh, Joseph S. Wall, James F. Hainfeld

Biomedical Sciences Faculty Research and Publications

Elongated fibrinogen molecules are comprised of two outer “D” domains, each connected through a “coiled-coil” region to the central “E” domain. Fibrin forms following thrombin cleavage in the E domain and then undergoes intermolecular end-to-middle D:E domain associations that result in double-stranded fibrils. Factor XIIIa mediates crosslinking of the C-terminal regions of γ chains in each D domain (the γXL site) by incorporating intermolecular ɛ-(γ-glutamyl)lysine bonds between amine donor γ406 lysine of one γ chain and a glutamine acceptor at γ398 or γ399 of another. Several lines of evidence show that crosslinked γ chains extend “transversely” between the strands of …

Identification And Characterization Of The Thrombin Binding Sites On Fibrin, David A. Meh, Kevin R. Siebenlist, Michael W. Mosesson

Biomedical Sciences Faculty Research and Publications

Thrombin binds to fibrin at two classes of non-substrate sites, one of high affinity and the other of low affinity. We investigated the location of these thrombin binding sites by assessing the binding of thrombin to fibrin lacking or containing γ′ chains, which are fibrinogen γ chain variants that contain a highly anionic carboxyl-terminal sequence. We found the high affinity thrombin binding site to be located exclusively in D domains on γ′ chains (K_a, 4.9 × 10⁶⁻¹; n, 1.05 per γ′ chain), whereas the low affinity thrombin binding site was in the fibrin E …