Identification of lactate as a driving force for prostanoid transport by prostaglandin transporter PGT.
We previously characterized the prostaglandin (PG) transporter PGT as an exchanger in which [(3)H]PGE(2) influx is coupled to the efflux of a countersubstrate. Here, we cultured HeLa cells that stably expressed human PGT under conditions known to favor glycolysis (glucose as a carbon source) or oxidative phosphorylation (glutamine as a carbon source) and studied the effect on PGT-mediated [(3)H]PGE(2) influx. PGT-expressing cells grown in glutamine exhibited a 2- to 4-fold increase in [(3)H]PGE(2) influx compared with the antisense control, whereas cells grown in glucose exhibited a 14-fold increase. In the presence of 10 vs. 25 mM glucose during the uptake, there was a dose-dependent increment in [(3)H]PGE(2) influx. Cis inhibition of [(3)H]PGE(2) influx occurred with lactate at physiological concentrations (apparent K(m) = 48 +/- 12 mM). Preloading with lactate caused a dose-dependent trans stimulation of PGT-mediated [(3)H]PGE(2) uptake, and external lactate caused trans stimulation of PGT-mediated [(3)H]PGE(2) release. Together, these data are consistent with PGT-mediated PG-lactate exchange. Cells engaged in glycolysis would then be poised energetically for prostanoid uptake by means of PGT.
Chan
Brenda S
BS
Department of Medicine, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
Endo
Shinichi
S
Kanai
Naoaki
N
Schuster
Victor L
VL
D017920:Antiporters / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D003847:Deoxyglucose / Q000494:pharmacology; D015232:Dinoprostone / Q000378:metabolism / Q000493:pharmacokinetics; D004305:Dose-Response Relationship, Drug; D015870:Gene Expression; D005947:Glucose / Q000378:metabolism / Q000494:pharmacology; D005973:Glutamine / Q000378:metabolism; D006019:Glycolysis / Q000502:physiology; D006367:HeLa Cells; D006801:Humans; D019344:Lactic Acid / Q000378:metabolism* / Q000494:pharmacology; D027361:Organic Anion Transporters; D010085:Oxidative Phosphorylation; D011453:Prostaglandins / Q000378:metabolism* / Q000493:pharmacokinetics; D014162:Transfection
D017920:Antiporters; D004268:DNA-Binding Proteins; D027361:Organic Anion Transporters; D011453:Prostaglandins; C503526:SLCO2A1 protein, human; D005973:Glutamine; D019344:Lactic Acid; D003847:Deoxyglucose; D005947:Glucose; D015232:Dinoprostone