An asymmetric contribution to gamma-aminobutyric type a receptor function of a conserved lysine within TM2-3 of alpha 1, beta 2, and gamma 2 subunits

Tim G. Hales, Terek Z. Deeb, Haiyan Tang, Karen A. Bollan, Dale P. King, Sara J. Johnson, Christopher N Connolly

    Research output: Contribution to journalArticle

    26 Citations (Scopus)

    Abstract

    Mutations that impair the expression and/or function of gamma-aminobutyric acid type A (GABA(A)) receptors can lead to epilepsy. The familial epilepsy gamma 2(K289M) mutation affects a basic residue conserved in the TM2-3 linker of most GABA(A) subunits. We investigated the effect on expression and function of the Lys -> Met mutation in mouse alpha 1(K278M), beta 2(K274M), and gamma 2( K289M) subunits. Compared with cells expressing wild-type and alpha 1 beta 2 gamma 2(K289M) receptors, cells expressing alpha 1(K278M)beta 2 gamma 2 and alpha 1 beta 2(K274M)gamma 2 receptors exhibited reduced agonist-evoked current density and reduced GABA potency, with no change in single channel conductance. The low current density of alpha 1 beta 2(K274M)gamma 2 receptors coincided with reduced surface expression. By contrast the surface expression of alpha 1(K278M)beta 2 gamma 2 receptors was similar to wild-type and alpha 1 beta 2 gamma 2(K289M) receptors suggesting that the alpha 1(K278M) impairs function. In keeping with this interpretation GABA-activated channels mediated by alpha 1(K278M)gamma 2 receptors had brief open times. To a lesser extent gamma 2(K289M) also reduced mean open time, whereas beta 2(K274M) had no effect. We used propofol as an alternative GABA(A) receptor agonist to test whether the functional deficits of mutant subunits were specific to GABA activation. Propofol was less potent as an activator of alpha 1(K278M)beta 2 gamma 2 receptors. By contrast, neither beta 2(K274M) nor gamma 2(K289M) affected the potency of propofol. The beta 2(K274M) construct was unique in that it reduced the efficacy of propofol activation relative to GABA. These data suggest that the alpha 1 subunit Lys-278 residue plays a pivotal role in channel gating that is not dependent on occupancy of the GABA binding site. Moreover, the conserved TM2-3 loop lysine has an asymmetric function in different GABAA subunits.

    Original languageEnglish
    Pages (from-to)17034-17043
    Number of pages10
    JournalJournal of Biological Chemistry
    Volume281
    Issue number25
    DOIs
    Publication statusPublished - 23 Jun 2006

    Cite this

    @article{e7d5c63c32834c8ea9dd99fa52cf0dd1,
    title = "An asymmetric contribution to gamma-aminobutyric type a receptor function of a conserved lysine within TM2-3 of alpha 1, beta 2, and gamma 2 subunits",
    abstract = "Mutations that impair the expression and/or function of gamma-aminobutyric acid type A (GABA(A)) receptors can lead to epilepsy. The familial epilepsy gamma 2(K289M) mutation affects a basic residue conserved in the TM2-3 linker of most GABA(A) subunits. We investigated the effect on expression and function of the Lys -> Met mutation in mouse alpha 1(K278M), beta 2(K274M), and gamma 2( K289M) subunits. Compared with cells expressing wild-type and alpha 1 beta 2 gamma 2(K289M) receptors, cells expressing alpha 1(K278M)beta 2 gamma 2 and alpha 1 beta 2(K274M)gamma 2 receptors exhibited reduced agonist-evoked current density and reduced GABA potency, with no change in single channel conductance. The low current density of alpha 1 beta 2(K274M)gamma 2 receptors coincided with reduced surface expression. By contrast the surface expression of alpha 1(K278M)beta 2 gamma 2 receptors was similar to wild-type and alpha 1 beta 2 gamma 2(K289M) receptors suggesting that the alpha 1(K278M) impairs function. In keeping with this interpretation GABA-activated channels mediated by alpha 1(K278M)gamma 2 receptors had brief open times. To a lesser extent gamma 2(K289M) also reduced mean open time, whereas beta 2(K274M) had no effect. We used propofol as an alternative GABA(A) receptor agonist to test whether the functional deficits of mutant subunits were specific to GABA activation. Propofol was less potent as an activator of alpha 1(K278M)beta 2 gamma 2 receptors. By contrast, neither beta 2(K274M) nor gamma 2(K289M) affected the potency of propofol. The beta 2(K274M) construct was unique in that it reduced the efficacy of propofol activation relative to GABA. These data suggest that the alpha 1 subunit Lys-278 residue plays a pivotal role in channel gating that is not dependent on occupancy of the GABA binding site. Moreover, the conserved TM2-3 loop lysine has an asymmetric function in different GABAA subunits.",
    author = "Hales, {Tim G.} and Deeb, {Terek Z.} and Haiyan Tang and Bollan, {Karen A.} and King, {Dale P.} and Johnson, {Sara J.} and Connolly, {Christopher N}",
    year = "2006",
    month = "6",
    day = "23",
    doi = "10.1074/jbc.M603599200",
    language = "English",
    volume = "281",
    pages = "17034--17043",
    journal = "Journal of Biological Chemistry",
    issn = "0021-9258",
    publisher = "American Society for Biochemistry and Molecular Biology",
    number = "25",

    }

    An asymmetric contribution to gamma-aminobutyric type a receptor function of a conserved lysine within TM2-3 of alpha 1, beta 2, and gamma 2 subunits. / Hales, Tim G. ; Deeb, Terek Z. ; Tang, Haiyan; Bollan, Karen A. ; King, Dale P. ; Johnson, Sara J. ; Connolly, Christopher N .

    In: Journal of Biological Chemistry, Vol. 281, No. 25, 23.06.2006, p. 17034-17043.

    Research output: Contribution to journalArticle

    TY - JOUR

    T1 - An asymmetric contribution to gamma-aminobutyric type a receptor function of a conserved lysine within TM2-3 of alpha 1, beta 2, and gamma 2 subunits

    AU - Hales, Tim G.

    AU - Deeb, Terek Z.

    AU - Tang, Haiyan

    AU - Bollan, Karen A.

    AU - King, Dale P.

    AU - Johnson, Sara J.

    AU - Connolly, Christopher N

    PY - 2006/6/23

    Y1 - 2006/6/23

    N2 - Mutations that impair the expression and/or function of gamma-aminobutyric acid type A (GABA(A)) receptors can lead to epilepsy. The familial epilepsy gamma 2(K289M) mutation affects a basic residue conserved in the TM2-3 linker of most GABA(A) subunits. We investigated the effect on expression and function of the Lys -> Met mutation in mouse alpha 1(K278M), beta 2(K274M), and gamma 2( K289M) subunits. Compared with cells expressing wild-type and alpha 1 beta 2 gamma 2(K289M) receptors, cells expressing alpha 1(K278M)beta 2 gamma 2 and alpha 1 beta 2(K274M)gamma 2 receptors exhibited reduced agonist-evoked current density and reduced GABA potency, with no change in single channel conductance. The low current density of alpha 1 beta 2(K274M)gamma 2 receptors coincided with reduced surface expression. By contrast the surface expression of alpha 1(K278M)beta 2 gamma 2 receptors was similar to wild-type and alpha 1 beta 2 gamma 2(K289M) receptors suggesting that the alpha 1(K278M) impairs function. In keeping with this interpretation GABA-activated channels mediated by alpha 1(K278M)gamma 2 receptors had brief open times. To a lesser extent gamma 2(K289M) also reduced mean open time, whereas beta 2(K274M) had no effect. We used propofol as an alternative GABA(A) receptor agonist to test whether the functional deficits of mutant subunits were specific to GABA activation. Propofol was less potent as an activator of alpha 1(K278M)beta 2 gamma 2 receptors. By contrast, neither beta 2(K274M) nor gamma 2(K289M) affected the potency of propofol. The beta 2(K274M) construct was unique in that it reduced the efficacy of propofol activation relative to GABA. These data suggest that the alpha 1 subunit Lys-278 residue plays a pivotal role in channel gating that is not dependent on occupancy of the GABA binding site. Moreover, the conserved TM2-3 loop lysine has an asymmetric function in different GABAA subunits.

    AB - Mutations that impair the expression and/or function of gamma-aminobutyric acid type A (GABA(A)) receptors can lead to epilepsy. The familial epilepsy gamma 2(K289M) mutation affects a basic residue conserved in the TM2-3 linker of most GABA(A) subunits. We investigated the effect on expression and function of the Lys -> Met mutation in mouse alpha 1(K278M), beta 2(K274M), and gamma 2( K289M) subunits. Compared with cells expressing wild-type and alpha 1 beta 2 gamma 2(K289M) receptors, cells expressing alpha 1(K278M)beta 2 gamma 2 and alpha 1 beta 2(K274M)gamma 2 receptors exhibited reduced agonist-evoked current density and reduced GABA potency, with no change in single channel conductance. The low current density of alpha 1 beta 2(K274M)gamma 2 receptors coincided with reduced surface expression. By contrast the surface expression of alpha 1(K278M)beta 2 gamma 2 receptors was similar to wild-type and alpha 1 beta 2 gamma 2(K289M) receptors suggesting that the alpha 1(K278M) impairs function. In keeping with this interpretation GABA-activated channels mediated by alpha 1(K278M)gamma 2 receptors had brief open times. To a lesser extent gamma 2(K289M) also reduced mean open time, whereas beta 2(K274M) had no effect. We used propofol as an alternative GABA(A) receptor agonist to test whether the functional deficits of mutant subunits were specific to GABA activation. Propofol was less potent as an activator of alpha 1(K278M)beta 2 gamma 2 receptors. By contrast, neither beta 2(K274M) nor gamma 2(K289M) affected the potency of propofol. The beta 2(K274M) construct was unique in that it reduced the efficacy of propofol activation relative to GABA. These data suggest that the alpha 1 subunit Lys-278 residue plays a pivotal role in channel gating that is not dependent on occupancy of the GABA binding site. Moreover, the conserved TM2-3 loop lysine has an asymmetric function in different GABAA subunits.

    U2 - 10.1074/jbc.M603599200

    DO - 10.1074/jbc.M603599200

    M3 - Article

    VL - 281

    SP - 17034

    EP - 17043

    JO - Journal of Biological Chemistry

    JF - Journal of Biological Chemistry

    SN - 0021-9258

    IS - 25

    ER -