Alanine serine cysteine transporter (ASCT) substrate binding site properties probed with hydroxyhomoserine esters

Design strategies and recent development of bioactive modulators for glutamine transporters

Glutamine transporters are integral to the metabolism of glutamine in both healthy tissues and cancerous cells, playing a pivotal role in maintaining amino acid balance, synthesizing biomolecules, and regulating redox equilibrium. Their critical functions in cellular metabolism make them promising targets for oncological therapies. Recent years have witnessed substantial progress in the field of glutamine transporters, marked by breakthroughs in understanding of their protein structures and the discovery of novel inhibitors, prodrugs, and radiotracers. This review provides a comprehensive update on the latest advancements in modulators targeting the glutamine transporter, with special attention given to LAT1 and ASCT2. It also discusses innovative approaches in drug design aimed at these transporters.

Exploring Amino Acid Transporters as Therapeutic Targets for Cancer: An Examination of Inhibitor Structures, Selectivity Issues, and Discovery Approaches

Amino acid transporters are abundant amongst the solute carrier family and have an important role in facilitating the transfer of amino acids across cell membranes. Because of their impact on cell nutrient distribution, they also appear to have an important role in the growth and development of cancer. Naturally, this has made amino acid transporters a novel target of interest for the development of new anticancer drugs. Many attempts have been made to develop inhibitors of amino acid transporters to slow down cancer cell growth, and some have even reached clinical trials. The purpose of this review is to help organize the available information on the efforts to discover amino acid transporter inhibitors by focusing on the amino acid transporters ASCT2 (SLC1A5), LAT1 (SLC7A5), xCT (SLC7A11), SNAT1 (SLC38A1), SNAT2 (SLC38A2), and PAT1 (SLC36A1). We discuss the function of the transporters, their implication in cancer, their known inhibitors, issues regarding selective inhibitors, and the efforts and strategies of discovering inhibitors. The goal is to encourage researchers to continue the search and development within the field of cancer treatment research targeting amino acid transporters.

Investigations of potential non-amino acid SNAT2 inhibitors

The sodium-coupled neutral amino acid transporter 2 (SNAT2, SLC38A2) has been implicated in cancer for its ability to supply cancer cells with glutamine and sarcosine. A recent high-throughput screen published by Gauthier-Coles et al. identified the non-amino acid 3-(N-methyl (4-methylphenyl)sulfonamido)-N-(2-trifluoromethylbenzyl)thiophene-2-carboxamide (MMTC or 57E) as a potent and selective SNAT2 inhibitor. Here we have investigated the ability of MMTC and four other compounds selected from the screen by Gauthier-Coles et al. to decrease 3H-Gly uptake in hyperosmotically treated human prostate cancer PC-3 cells. In these cells, SNAT2 is highly upregulated when the cells are hyperosmotically stressed for 24 h and is the primary contributor to glycine uptake. The five compounds were investigated at concentrations of 1-50 µM based on their equilibrium solubility. At 37°C the equilibrium solubility in HEPES buffered HBSS at pH 7.4 was measured to be 24.9 (53B), 56.1 (54F), 13.3 (55B), and 27.5 (57B) µM, respectively. The equilibrium solubility of MMTC was below the detection limit of the HPLC-UV method, thus less than 1.8 µM. However, a kinetic solubility of approximately 2.5-10 µM could be achieved during the course of the uptake study. In contrast to the previous publication, MMTC showed no inhibition of SNAT2-mediated 3H-Gly uptake in PC-3 cells at a concentration of 1 or 5 μM, despite a published IC50 of 0.8 µM. Similarly, 53B, 55B, and 57B showed no inhibition at soluble conditions, whereas 54F showed approximately 20% inhibition at 50 µM. In our experimental setup, the investigated compounds showed limited potential as SNAT2 inhibitors.

d-Amino acids: new clinical pathways for brain diseases

Free d-amino acids (d-AAs) are emerging as a novel and important class of signaling molecules in many organs, including the brain and endocrine systems. There has been considerable progress in our understanding of the fundamental roles of these atypical messengers, with increasingly recognized implications in a wide range of neuropathologies, including schizophrenia (SCZ), epilepsy, Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS), substance abuse, and chronic pain, among others. Research has enabled the discovery that d-serine, d-aspartate and more recently d-cysteine are essential for the healthy development and function of the central nervous system (CNS). We discuss recent progress that has profoundly transformed our vision of numerous physiological processes but has also shown how d-AAs are now offering therapeutic promise in clinical settings for several human diseases.