ATP modulates SLC7A5 (LAT1) synergistically with cholesterol

Abstract

The plasma membrane transporter hLAT1 is responsible for providing cells with essential amino acids. hLAT1 is over-expressed in virtually all human cancers making the protein a hot-spot in the fields of cancer and pharmacology research. However, regulatory aspects of hLAT1 biology are still poorly understood. A remarkable stimulation of transport activity was observed in the presence of physiological levels of cholesterol together with a selective increase of the affinity for the substrate on the internal site, suggesting a stabilization of the inward open conformation of hLAT1. A synergistic effect by ATP was also observed only in the presence of cholesterol. The same phenomenon was detected with the native protein. Altogether, the biochemical assays suggested that cholesterol and ATP binding sites are close to each other. The computational analysis identified two neighboring regions, one hydrophobic and one hydrophilic, to which cholesterol and ATP were docked, respectively. The computational data predicted interaction of the ϒ-phosphate of ATP with Lys 204, which was confirmed by site-directed mutagenesis. The hLAT1-K204Q mutant showed an impaired function and response to ATP. Interestingly, this residue is conserved in several members of the SLC7 family.

Amino Acid Transporter LAT1 (SLC7A5) Mediates MeHg-Induced Oxidative Stress Defense in the Human Placental Cell Line HTR-8/SVneo

“…However, a recent study found elevated LAT1 levels in FGR and preeclamptic placentas, which the authors interpreted as a compensatory mechanism [41]. This is in line with our results, thus strengthening the notion of a regulating role of LAT1 in these conditions by supplying amino acids for GSH synthesis to ameliorate accompanying oxidative stress [42,43].…”

Metabolism of Amino Acids in Cancer

“…LAT1 ( SLC7A5 ) is the main BCAA transporter, which belongs to the Na + - and pH-independent L-type amino acid transporters (system L/antiporter) SLC7 family and is highly expressed in many cancers, including the most frequently diagnosed cancers, such as lung cancer, prostate cancer, and breast cancer (Kandasamy et al, 2018 ; Singh and Ecker, 2018 ; Hafliger and Charles, 2019 ). Notably, a recent study found that LAT1 was a pH-dependent but not pH-independent transporter, whose maximal transporter activity is at neutral pH but much lower at acidic pH (Cosco et al, 2020 ). LAT1 ( SLC7A5 ) imports BCAAs and several essential amino acids (e.g., phenylalanine, leucine, isoleucine, tryptophan, histidine, and tyrosine) with high affinity in exchange for the efflux of intracellular histidine, tyrosine, and glutamine (Nicklin et al, 2009 ; Puris et al, 2020 ).…”

Yeast Cell-Based Transport Assay for the Functional Characterization of Human 4F2hc-LAT1 and ‐LAT2, and LAT1 and LAT2 Substrates and Inhibitors

“…The methylotrophic yeast Pichia pastoris represents a wellestablished system for the expression of recombinant human membrane proteins (Byrne, 2015). Cholesterol and derivatives thereof were shown to play an important role in function and stability of LATs (Meury et al, 2014;Dickens et al, 2017;Cosco et al, 2020). Yeasts such as P. pastoris produce ergosterol (Nes et al, 1978) providing a valuable cholesterol derivate for interaction with heterologously expressed membrane proteins.…”