Modulation of succinate transport in Hep G2 cell line by PKC.
The cellular uptake of the tricarboxylic acid cycle (TCA) intermediates is very important for cellular metabolism. However, the transport pathways for these intermediates in liver cells are not well characterized. We have examined the transport of succinate and citrate in the human hepatoma cell line Hep G2 and found that it exhibited a higher rate of succinate compared to citrate transport, which was sodium dependent. Comparison of the transport properties of Hep G2 to that of human retinal pigment epithelial (HRPE) cells transfected with human sodium dicarboxylate transporters, hNaDC-1, hNaDC-3, and hNaCT indicated that Hep G2 cells express a combination of hNaDC-3 and hNaCT. Short period activation of protein kinase C (PKC) by phorbol 12-myristate, 13-acetate (PMA) and alpha-adrenergic receptor agonist, phenylephrine (PE), downregulated sodium-dependent succinate transport presumably via hNaDC-3. The inhibition by PMA was partially prevented by cytochalasin D, suggesting that PKC reduces the hNaDC-3 activity, at least in part, by increased endocytosis. In contrast, activation of PKA by both forskolin and epidermal growth factor (EGF) had no effect on succinate transport. Our results suggest that Hep G2 cells provide a useful model for studies of di- and tricarboxylate regulation of human liver.
Srisawang
Piyarat
P
Department of Physiology, Faculty of Science, Mahidol University, Bangkok 10400, Thailand.
Chatsudthipong
Atip
A
Chatsudthipong
Varanuj
V
D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D045744:Cell Line, Tumor; D002952:Citric Acid Cycle / Q000502:physiology*; D015638:Cytochalasin D; D017931:DNA Primers; D029382:Dicarboxylic Acid Transporters / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008099:Liver / Q000378:metabolism*; D029363:Organic Anion Transporters, Sodium-Dependent / Q000378:metabolism; D010656:Phenylephrine / Q000494:pharmacology; D010703:Phorbol Esters / Q000494:pharmacology; D010857:Pigment Epithelium of Eye / Q000166:cytology / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019802:Succinic Acid / Q000378:metabolism*; D027981:Symporters / Q000378:metabolism
D017931:DNA Primers; D029382:Dicarboxylic Acid Transporters; D029363:Organic Anion Transporters, Sodium-Dependent; D010703:Phorbol Esters; C092524:SLC13A2 protein, human; C470492:SLC13A5 protein, human; D027981:Symporters; D010656:Phenylephrine; D015638:Cytochalasin D; D019802:Succinic Acid; D011493:Protein Kinase C