title: The properties, functions, and pathophysiology of maxi-anion channels.
abstract: The maxi-anion channels (MACs) with a unitary conductance of 200-500 pS are detected in virtually every part of the whole body and found in cells from mammals to amphibia. The channels are normally silent but can be activated by physiologically/pathophysiologically relevant stimuli, such as osmotic, salt, metabolic, oxidative, and mechanical stresses, receptor activation, serum, heat, and intracellular Ca(2+) rise. In some MACs, protein dephosphorylation is associated with channel activation. Among MACs so far studied, around 60 % (designated here as Maxi-Cl) possess, in common, the following phenotypical biophysical properties: (1) unitary conductance of 300-400 pS, (2) a linear current-voltage relationship, (3) high anion-to-cation selectivity with PCl/Pcation of >8, and (4) inactivation at positive and negative potentials over a certain level (usually ±20 mV). The pore configuration of the Maxi-Cl is asymmetrical with extracellular and intracellular radii of ∼1.42 and ∼1.16 nm, respectively, and a medial constriction down to ∼0.55-0.75 nm. The classical function of MACs is control of membrane potential and fluid movement. Permeability to ATP and glutamate turns MACs to signaling channels in purinergic and glutamatergic signal transduction defining them as a perspective target for drug discovery. The molecular identification is an urgent task that would greatly promote the developments in this field. A possible relationship between these channels and some transporters is discussed.
authors.affiliation: Department of Cell Physiology, National Institute for Physiological Sciences, Okazaki, 444-8787, Japan. sabirov@nips.ac.jp.|Laboratory of Molecular Physiology, Institute of Bioorganic Chemistry, Uzbekistan Academy of Sciences, Tashkent, 100125, Uzbekistan. sabirov@nips.ac.jp.
authors.forename: Ravshan Z
authors.initials: RZ
authors.lastname: Sabirov
authors.affiliation: Department of Cell Physiology, National Institute for Physiological Sciences, Okazaki, 444-8787, Japan.|Laboratory of Molecular Physiology, Institute of Bioorganic Chemistry, Uzbekistan Academy of Sciences, Tashkent, 100125, Uzbekistan.
authors.forename: Petr G
authors.initials: PG
authors.lastname: Merzlyak
authors.affiliation: Department of Cell Physiology, National Institute for Physiological Sciences, Okazaki, 444-8787, Japan.
authors.forename: Md Rafiqul
authors.initials: MR
authors.lastname: Islam
authors.affiliation: Department of Cell Physiology, National Institute for Physiological Sciences, Okazaki, 444-8787, Japan.
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Okada
authors.affiliation: Department of Cell Physiology, National Institute for Physiological Sciences, Okazaki, 444-8787, Japan. okada@soken.ac.jp.|SOKENDAI (The Graduate University for Advanced Studies), Shonan Village, Hayama, Kanagawa, 240-0193, Japan. okada@soken.ac.jp.
authors.forename: Yasunobu
authors.initials: Y
authors.lastname: Okada
mesh_terms: D000200:Action Potentials; D000818:Animals; D018118:Chloride Channels / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D017136:Ion Transport; D010641:Phenotype; D015398:Signal Transduction
chemical_list: D018118:Chloride Channels
keywords: ATP release; Biophysical properties; Glutamate release; Maxi-anion channels; Purinergic signaling