title: Endogenous and synthetic neuroactive steroids evoke sustained increases in the efficacy of GABAergic inhibition via a protein kinase C-dependent mechanism.
abstract: The neuroactive steroid (NAS) tetrahydrodeoxycorticosterone (THDOC) increases protein kinase C (PKC) mediated phosphorylation of extrasynaptic GABAAreceptor (GABAAR) subunits leading to increased surface expression of α4/β3 subunit-containing extrasynaptic GABAARs, leading to a sustained increase in GABAAR tonic current density. Whether other naturally occurring and synthetic NASs share both an allosteric and metabotropic action on GABAARs is unknown. Here, we examine the allosteric and metabotropic properties of allopregnanolone (ALLO), and synthetic NASs SGE-516 and ganaxolone. ALLO, SGE-516, and ganaxolone all allosterically enhanced prototypical synaptic and extrasynaptic recombinant GABAARs. In dentate gyrus granule cells (DGGCs) all three NASs, when applied acutely, allosterically enhanced tonic and phasic GABAergic currents. In separate experiments, slices were exposed to NASs for 15 min, and then transferred to a steroid naïve recording chamber followed by ≥ 30 min wash before tonic currents were measured. A sustained increase in tonic current was observed following exposure to ALLO, or SGE-516 and was prevented by inhibiting PKC with GF 109203X. No increase in tonic current was observed with exposure to ganaxolone. In agreement with the observations of an increased tonic current, the NASs ALLO and SGE-516 increased the phosphorylation and surface expression of the β3 subunit-containing GABAARs. Our studies demonstrate that neuroactive steroids have differential abilities to induce sustained increases in the efficacy of tonic inhibition by promoting GABAAR phosphorylation and membrane trafficking dependent on PKC activity.
authors.affiliation: Tufts University School of Medicine, Department of Neuroscience, 136 Harrison Ave, Boston, MA 02111, USA.
authors.forename: Amit
authors.initials: A
authors.lastname: Modgil
authors.affiliation: Tufts University School of Medicine, Department of Neuroscience, 136 Harrison Ave, Boston, MA 02111, USA.
authors.forename: Manasa L
authors.initials: ML
authors.lastname: Parakala
authors.affiliation: Sage Therapeutics, Inc., 215 First St, Cambridge, MA, USA.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Ackley
authors.affiliation: Sage Therapeutics, Inc., 215 First St, Cambridge, MA, USA.
authors.forename: James J
authors.initials: JJ
authors.lastname: Doherty
authors.affiliation: Tufts University School of Medicine, Department of Neuroscience, 136 Harrison Ave, Boston, MA 02111, USA; Department of Neuroscience, Physiology and Pharmacology, University College, London WC1E6BT, United Kingdom.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Moss
authors.affiliation: Tufts University School of Medicine, Department of Neuroscience, 136 Harrison Ave, Boston, MA 02111, USA. Electronic address: paul.davies@tufts.edu.
authors.forename: Paul A
authors.initials: PA
authors.lastname: Davies
mesh_terms: D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D003900:Desoxycorticosterone / Q000031:analogs & derivatives* / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D057809:HEK293 Cells; D006624:Hippocampus; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D008297:Male; D008301:Maleimides / Q000494:pharmacology; D051379:Mice; D008810:Mice, Inbred C57BL; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology*; D009924:Organ Culture Techniques; D011280:Pregnanolone / Q000494:pharmacology*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011963:Receptors, GABA-A / Q000378:metabolism*
chemical_list: D004791:Enzyme Inhibitors; D007211:Indoles; D008301:Maleimides; D011963:Receptors, GABA-A; D003900:Desoxycorticosterone; C009413:tetrahydrodeoxycorticosterone; D011280:Pregnanolone; D011493:Protein Kinase C; C070515:bisindolylmaleimide I
keywords: Dentate gyrus; GABA receptor; Neuroactive steroid; Protein kinase C (PKC); Tonic inhibition