Energy-driven uptake of the neurotoxin 1-methyl-4-phenylpyridinium into chromaffin granules via the catecholamine transporter.
Chromaffin granules take up and concentrate 1-methyl-4-phenylpyridinium (MPP+) through a temperature-sensitive and saturable mechanism. The uptake displays an apparent Km of 51.2 microM and a Vmax of 7.1 nmol/min/mg of protein. MPP+ uptake is markedly depressed in the absence of ATP or by inhibition of the membrane Mg2+-dependent ATPase, and it is completely blocked by reserpine. Reversal of the membrane potential by carbonyl cyanide m-chlorophenylhydrazone or dissipation of the pH gradient in the presence of nigericin plus potassium ions produces a marked inhibition of MPP+ uptake indicating that the process is dependent upon the integrity of the transmembrane proton electrochemical gradient generated and maintained by the membrane Mg2+-dependent ATPase. Furthermore, the data shows that a permanently charged compound is capable of entering the granule through the catecholamine carrier.
Daniels
A J
AJ
Department of Medicinal Biochemistry, Wellcome Research Laboratories, Research Triangle Park, North Carolina 27709.
Reinhard
J F
JF
D015655:1-Methyl-4-phenylpyridinium; D000313:Adrenal Medulla / Q000166:cytology / Q000187:drug effects; D000643:Ammonium Chloride / Q000494:pharmacology; D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D002352:Carrier Proteins / Q000378:metabolism*; D050482:Catecholamine Plasma Membrane Transport Proteins; D002417:Cattle; D002837:Chromaffin Granules / Q000187:drug effects / Q000378:metabolism*; D002838:Chromaffin System / Q000378:metabolism*; D004298:Dopamine / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D026901:Membrane Transport Proteins; D009498:Neurotoxins / Q000378:metabolism*; D009550:Nigericin / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D011726:Pyridinium Compounds / Q000378:metabolism*; D012701:Serotonin / Q000494:pharmacology
D002352:Carrier Proteins; D050482:Catecholamine Plasma Membrane Transport Proteins; D026901:Membrane Transport Proteins; D009498:Neurotoxins; D011726:Pyridinium Compounds; D000643:Ammonium Chloride; D012701:Serotonin; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D015655:1-Methyl-4-phenylpyridinium; D009550:Nigericin; D011188:Potassium; D004298:Dopamine