Human Na+-coupled citrate transporter: primary structure, genomic organization, and transport function

Species-Specific Influence of Lithium on the Activity of SLC13A5 (NaCT): Lithium-Induced Activation Is Specific for the Transporter in Primates

“…The difference in substrate affinity for human NaCT between the mammalian cell expression system and the oocyte expression system is interesting. We have shown previously a similar difference between HepG2 cells and the mammalian cell expression system (Inoue et al, 2002b;Gopal et al, 2007). The human NaCT cDNA was isolated from a HepG2 cell cDNA library (Inoue et al, 2002b).…”

“…We have shown previously a similar difference between HepG2 cells and the mammalian cell expression system (Inoue et al, 2002b;Gopal et al, 2007). The human NaCT cDNA was isolated from a HepG2 cell cDNA library (Inoue et al, 2002b). When this cDNA was expressed in HRPE cells, the affinity for citrate was ∼650 mM (Inoue et al, 2002b).…”

“…NaCT is identified as SLC13A5 according to the Human Genome Organization nomenclature (Markovich and Murer, 2004;Pajor, 2006). In humans, SLC13A5 mRNA is expressed abundantly in the liver and to a much lesser extent in the brain and testes (Inoue et al, 2002b). In the rat, however, the transporter mRNA is expressed in the liver and testes with comparable abundance and at relatively much lower levels in the brain (Inoue et al, 2002a).…”

“…The rat and mouse NaCTs recognize citrate with high affinity (K t : rat, ∼20 mM; mouse, ∼40 mM), but these transporters also interact with succinate with appreciable affinity (K t : rat, ∼170 mM; mouse, ∼40 mM) (Inoue et al, 2002a. In contrast, human NaCT exhibits relatively lower affinity for citrate (K t , ∼600 mM) but is relatively more selective for citrate (Inoue et al, 2002b). Based on substrate specificity, NaCT is the mammalian functional ortholog of Indy (I am not dead yet) in Drosophila (Rogina et al, 2000) even though the mammalian NaCT is Na 1 dependent, whereas the Drosophila Indy is Na 1 independent (Inoue et al, 2002c;Knauf et al, 2002Knauf et al, , 2006.…”

“…The human NaCT cDNA was isolated from a HepG2 cell cDNA library (Inoue et al, 2002b). When this cDNA was expressed in HRPE cells, the affinity for citrate was ∼650 mM (Inoue et al, 2002b). But when the activity of the constitutively expressed NaCT was monitored in HepG2 cells, the affinity for citrate was ∼5 mM (Gopal et al, 2007).…”