Nagamune H, Fukushima Y, Takada J, Yoshida K, Unami A, Shimooka T, Terada H. The lipophilic weak base (Z)-5-methyl-2-[2-(1-naphthyl)ethenyl]-4-piperidinopyridine (AU-1421) is a potent protonophore type cationic uncoupler of oxidative phosphorylation in mitochondria.
BIOCHIMICA ET BIOPHYSICA ACTA 1993;
1141:231-7. [PMID:
8382953 DOI:
10.1016/0005-2728(93)90047-j]
[Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The lipophilic weak base AU-1421 acts as a simple protonophoric uncoupler of oxidative phosphorylation in rat liver mitochondria judging from the following observations. In the absence of any carrier lipophilic anions or P(i), AU-1421 stimulated the rate of state 4 respiration maximally about 7-fold at a concentration of 30 nmol/mg mitochondrial protein. At the same maximum effective concentration, it also inhibited ATP synthesis, released oligomycin-inhibited state 3 respiration, dissipated the proton motive force in the energized state, and activated latent H(+)-ATPase. AU-1421 also allowed proton conduction in both mitochondrial membranes and liposomes. These actions of AU-1421 resemble those of the typical anionic uncoupler SF6847. A marked difference between the two was, however, that ATPase activation by AU-1421 was not suppressed at higher concentrations of AU-1421, whereas ATPase activated by SF6847 was suppressed on increase of the SF6847 concentration. The finding that this simple protonophoric cation acts as an uncoupler at a micromolar concentration is significant, because all true (i.e., protonophore type) uncouplers known so far are anionic not cationic. Thus, AU-1421 is a unique uncoupler of the protonophore type.
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