Involvement of Histidine Residue His382 in pH Regulation of MCT4 Activity.
Monocarboxylate transporter 4 (MCT4) is a pH-dependent bi-directional lactate transporter. Transport of lactate via MCT4 is increased by extracellular acidification. We investigated the critical histidine residue involved in pH regulation of MCT4 function. Transport of lactate via MCT4 was measured by using a Xenopus laevis oocyte expression system. MCT4-mediated lactate transport was inhibited by Zn2+ in a pH physiological condition but not in an acidic condition. The histidine modifier DEPC (diethyl pyrocarbonate) reduced MCT4 activity but did not completely inactivate MCT4. After treatment with DEPC, pH regulation of MCT4 function was completely knocked out. Inhibitory effects of DEPC were reversed by hydroxylamine and suppressed in the presence of excess lactate and Zn2+. Therefore, we performed an experiment in which the extracellular histidine residue was replaced with alanine. Consequently, the pH regulation of MCT4-H382A function was also knocked out. Our findings demonstrate that the histidine residue His382 in the extracellular loop of the transporter is essential for pH regulation of MCT4-mediated substrate transport activity.
Laboratory of Clinical Pharmaceutics & Therapeutics, Division of Pharmasciences, Faculty of Pharmaceutical Sciences, Hokkaido University, Kita-12-jo, Nishi-6-chome, Kita-ku, Sapporo 060-0812, Japan.
Shotaro
S
Sasaki
Laboratory of Clinical Pharmaceutics & Therapeutics, Division of Pharmasciences, Faculty of Pharmaceutical Sciences, Hokkaido University, Kita-12-jo, Nishi-6-chome, Kita-ku, Sapporo 060-0812, Japan.
Masaki
M
Kobayashi
Laboratory of Clinical Pharmaceutics & Therapeutics, Division of Pharmasciences, Faculty of Pharmaceutical Sciences, Hokkaido University, Kita-12-jo, Nishi-6-chome, Kita-ku, Sapporo 060-0812, Japan.
Yuya
Y
Futagi
Laboratory of Clinical Pharmaceutics & Therapeutics, Division of Pharmasciences, Faculty of Pharmaceutical Sciences, Hokkaido University, Kita-12-jo, Nishi-6-chome, Kita-ku, Sapporo 060-0812, Japan.
Jiro
J
Ogura
Laboratory of Clinical Pharmaceutics & Therapeutics, Division of Pharmasciences, Faculty of Pharmaceutical Sciences, Hokkaido University, Kita-12-jo, Nishi-6-chome, Kita-ku, Sapporo 060-0812, Japan.
Hiroaki
H
Yamaguchi
Laboratory of Clinical Pharmaceutics & Therapeutics, Division of Pharmasciences, Faculty of Pharmaceutical Sciences, Hokkaido University, Kita-12-jo, Nishi-6-chome, Kita-ku, Sapporo 060-0812, Japan; Department of Pharmacy, Hokkaido University Hospital, Sapporo 060-8648, Japan.
Ken
K
Iseki
D000818:Animals; D004047:Diethyl Pyrocarbonate / Q000494:pharmacology; D005260:Female; D006639:Histidine / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D019344:Lactic Acid / Q000378:metabolism; D027501:Monocarboxylic Acid Transporters / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D009124:Muscle Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D009865:Oocytes / Q000378:metabolism; D030781:Organisms, Genetically Modified / Q000235:genetics / Q000378:metabolism; D014982:Xenopus laevis / Q000235:genetics* / Q000378:metabolism; D015032:Zinc / Q000494:pharmacology
D027501:Monocarboxylic Acid Transporters; D009124:Muscle Proteins; C406962:SLC16A4 protein, human; D019344:Lactic Acid; D006639:Histidine; D015032:Zinc; D004047:Diethyl Pyrocarbonate