2004 — 2007 |
Fisher, Janet L |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Structural Determinants of Gaba-a Receptor Function @ University of South Carolina At Columbia
DESCRIPTION (provided by applicant): Gamma-aminobutyric acid (GABA) is the primary inhibitory neurotransmitter in the mammalian central nervous system, and most fast inhibitory neurotransmission in the brain is mediated by the GABAA receptors (GABARs). There are many families of GABAR subunits with multiple subtypes. The alpha subunit family is the largest, with six different subtypes (alpha1-alpha6). The expression of the subtypes is regulated regionally and developmentally and it is likely that each alpha subtype performs a unique physiological role. Subtype expression is also altered by pathological conditions, such as epilepsy. The subunit composition of the receptor affects many characteristics of the GABAR, but little is known about the effect of the identity of the alpha subtype on the channel's kinetic properties. The long-term goal of this work is to understand the functional significance of the structural heterogeneity of the GABAR and to determine which structural differences among the subunits underlie their different functional properties. The proposed work will examine this question by comparing the properties of recombinant receptors containing different alpha subtypes at the single channel, macropatch and whole-cell levels. The combination of these results will allow a complete description of the kinetic properties associated with each alpha subtype and may predict the behavior of synaptic receptors containing these subtypes. The structural differences responsible for distinct kinetic properties will be examined in detail for the alpha1and alpha 6 subtypes, which are the most functionally diverse in the alpha subunit family. To isolate the general structural domains responsible for the functional characteristics associated with each subtype, six chimeric alpha1 - alpha6 subunits will be examined. These chimeras were designed to isolate the functional contribution made from each of the four transmembrane domains. Once the general structural domains are isolated, the specific residues responsible for these characteristics will be identified through site-directed mutagenesis. The GABARs play an integral role in regulating neuronal activity. GABARs are important targets for drugs commonly used as sedatives, anxiolytics and anti-epileptics as well as for drugs of addiction, including barbiturates and alcohol. The activity of many of these modulators depends upon the alpha subtype composition of the receptor. The projects described will address the question of how structural differences among the alpha subtypes contribute to the functional properties of the channel. The results of this work will help us to understand how variations in the alpha subunit composition of native GABARs can affect the properties of neurons and their responses to GABA.
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0.94 |
2009 — 2013 |
Fisher, Janet L Mott, David D [⬀] |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Subunit Dependent Properties of Kainate Receptors @ University of South Carolina At Columbia
DESCRIPTION (provided by applicant): Kainate receptors are glutamate-gated ion channels that mediate synaptic transmission and regulate cellular excitability in the central nervous system. They contribute to cognitive processing by participating in the generation of rhythmic oscillations of hippocampal neurons at behaviorally relevant frequencies. Kainate receptors have also been implicated in a number of neurological disorders including temporal lobe epilepsy, schizophrenia, autism, and neuropathic pain. Rational development of novel therapies targeting these receptors depends upon a better understanding of their function. Kainate receptors are tetrameric and comprised of low affinity GluR5-7 and high affinity KA1 and KA2 subunits. Functional properties of kainite receptors depend upon their subunit composition. In particular, KA2-containing kainate receptors play a distinctive role in neuronal excitation. Current at KA2-containing kainate receptors exhibits a higher conductance and slower decay than that at KA2-lacking kainate receptors. In addition, KA2-containing kainate receptors enhance intrinsic neuronal excitability through a noncanonical metabotropic action. Perhaps because of their importance in neuronal excitation, receptors containing the KA2 subunit exhibit significantly increased sensitivity to modulation by a variety of endogenous agents, including protons, polyamines and zinc. While recent studies have shed light on the roles of KA2-containing kainate receptors in physiological conditions, little is known about how the expression of kainate receptor subunits or the functional role of these receptors changes in disease. Kainate receptors have long been implicated in mechanisms underlying temporal lobe epilepsy. A better understanding of how the properties and regulation of kainate receptors change in temporal lobe epilepsy would provide valuable information in the design of novel therapies for this disease. This project will examine the role of the KA2 subunit in kainate receptors in physiological conditions and in epilepsy. Aim 1 will use recombinant receptors to define the functional contribution of KA2 subunits to kainate receptors. Aim 2 will use lentiviral vectors and pharmacological agents to determine the effect of changes in KA2 subunit expression on KAR-mediated neurotransmission. Aim 3 will use quantitative real time qRT-PCR and immunohistochemistry to determine the time course of changes in KAR subunit RNA and protein in the hippocampus during the development of epilepsy after pilocarpine-induced status epilepticus (SE). Hippocampal slice electrophysiology combined with pharmacological agents and lentiviral vectors will then define how SE-induced alterations in subunit expression change functional properties of kainate receptors at these same time points. PUBLIC HEALTH RELEVANCE: Kainate receptors are glutamate-gated ion channels that are critical for synaptic transmission and can contribute to neurological diseases, such as temporal lobe epilepsy, schizophrenia, autism, and neuropathic pain. The goals of this study are to examine subunit dependent properties of these receptors and the impact of changes in subunit composition on hippocampal function. A better understanding of kainate receptor properties is essential in the rational development of novel therapeutic agents targeted at these receptors.
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0.94 |
2015 — 2016 |
Fisher, Janet L |
R03Activity Code Description: To provide research support specifically limited in time and amount for studies in categorical program areas. Small grants provide flexibility for initiating studies which are generally for preliminary short-term projects and are non-renewable. |
Regulation of Kainate-Type Glutamate Receptors by Auxiliary Subunits @ University of South Carolina At Columbia
? DESCRIPTION (provided by applicant): The ionotropic glutamate receptors are responsible for fast excitatory neurotransmission in the mammalian brain. There are three types of ionotropic glutamate receptors, named the AMPA, NMDA and kainate receptors. Kainate-type glutamate receptors are found in both pre- and post-synaptic locations, where they regulate neurotransmitter release and increase neuronal excitability. Dysregulation of kainate receptors has been linked to a variety of neurological disorders. In particular, abnormal expression patterns of these receptors may contribute to hyperexcitability of the hippocampus in temporal lobe epilepsy. The kainate receptors are tetrameric in structure, composed from a combination of five different pore-forming subunits (GluK1-GluK5). In addition, the kainate receptors can be regulated by co-assembly with the auxiliary subunits Neto1 and Neto2. Both the pore-forming and auxiliary subunits show distinct patterns of expression throughout the brain and may be regulated throughout development and in response to pathological conditions. The goal of this work is to determine the functional impact of subunit-specific interactions between pore-forming and auxiliary subunits, in order to predict the characteristics of neuronal receptors. In addition, we will use chimeric subunits and site-directed mutagenesis to determine the structural differences between the Neto1 and Neto2 subunits that give rise to their distinct functional effects. The results of this work will illuminate the roles that auxiliary subunits play in the regulation of excitatory neurotransmission and will suggest novel approaches for the treatment of neurological disorders through the targeted regulation of specific receptor populations.
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0.94 |