title: Peptides inhibitors of acid-sensing ion channels.
abstract: Acid-sensing ion channels (ASICs) channels are proton-gated cationic channels mainly expressed in central and peripheric nervous system and related to the epithelial amiloride-sensitive Na(+) channels and to the degenerin family of ion channels. ASICs comprise four proteins forming functional channel subunits (ASIC1a, ASIC1b, ASIC2a, and ASIC3) and two proteins (ASIC2b and ASIC4) without yet known activators. Functional channels are activated by external pH variations ranging from pH(0.5) 6.8 to 4.0 and currents are characterized by either rapid kinetics of inactivation (ASIC1a, ASIC1b, ASIC3) or slow kinetics of inactivation (ASIC2a) and sometimes the presence of a plateau phase (ASIC3). ASIC1a and ASIC3, which are expressed in nociceptive neurons, have been implicated in inflammation and knockout mice studies support the role of ASIC3 in various pain processes. ASIC1a seems more related to synaptic plasticity, memory, learning and fear conditioning in the CNS. ASIC2a contributes to hearing in the cochlea, sour taste sensation, and visual transduction in the retina. The pharmacology of ASICs is limited to rather nonselective drugs such as amiloride, nonsteroid anti-inflammatory drugs, and neuropeptides. Recently, two peptides, PcTx1 and APETx2, isolated from a spider and a sea anemone, have been characterized as selective and high-affinity inhibitors for ASIC1a and ASIC3 channels, respectively. PcTx1 inhibits ASIC1a homomers with an affinity of 0.7 nM (IC(50)) without any effect on ASIC1a containing heteromers and thus helped to characterize ASIC1a homomeric channels in peripheric and central neurons. PcTx1 acts as a gating modifier since it shifts the channel from the resting to an inactivated state by increasing its affinity for H(+). APETx2 is less selective since it inhibits several ASIC3-containing channels (IC(50) from 63 nM to 2 microM) and to date its mode of action is unknown. Nevertheless, APETx2 structure is related to other sea anemone peptides, which act as gating modifiers on Nav and Kv channels.
authors.affiliation: Institut de Pharmacologie Moléculaire et Cellulaire, Centre National de la Recherche Scientifique, Sophia-Antipolis, 660 Route des Lucioles, 06560 Valbonne, France.
authors.forename: S
authors.initials: S
authors.lastname: Diochot
authors.forename: M
authors.initials: M
authors.lastname: Salinas
authors.forename: A
authors.initials: A
authors.lastname: Baron
authors.forename: P
authors.initials: P
authors.lastname: Escoubas
authors.forename: M
authors.initials: M
authors.lastname: Lazdunski
mesh_terms: D062565:Acid Sensing Ion Channels; D000595:Amino Acid Sequence; D000818:Animals; D003064:Cnidarian Venoms / Q000235:genetics / Q000494:pharmacology*; D006801:Humans; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology; D008565:Membrane Proteins / Q000187:drug effects*; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000187:drug effects*; D012615:Sea Anemones; D016415:Sequence Alignment; D015222:Sodium Channels / Q000187:drug effects*; D013111:Spider Venoms / Q000235:genetics / Q000494:pharmacology*
chemical_list: C568266:ASIC1 protein, human; C568267:ASIC1 protein, mouse; C568270:ASIC4 protein, human; D062565:Acid Sensing Ion Channels; D003064:Cnidarian Venoms; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D015222:Sodium Channels; D013111:Spider Venoms