scholarly journals Chemical Approaches for Studying the Biology and Pharmacology of Membrane Transporters: The Histidine/Large Amino Acid Transporter SLC7A5 as a Benchmark

Molecules ◽  
2021 ◽  
Vol 26 (21) ◽  
pp. 6562
Author(s):  
Mariafrancesca Scalise ◽  
Raffaella Scanga ◽  
Lara Console ◽  
Michele Galluccio ◽  
Lorena Pochini ◽  
...  
Keyword(s):  
Amino Acid ◽  
Essential Amino Acids ◽  
Amino Acid Transporter ◽  
Membrane Transporters ◽  
Site Directed Mutagenesis ◽  
General Applicability ◽  
Regulatory Domains ◽  
Acid Transporter ◽  
Function Relationship ◽  
Basic Features

The localization of membrane transporters at the forefront of natural barriers makes these proteins very interesting due to their involvement in the absorption and distribution of nutrients and xenobiotics, including drugs. Over the years, structure/function relationship studies have been performed employing several strategies, including chemical modification of exposed amino acid residues. These approaches are very meaningful when applied to membrane transporters, given that these proteins are characterized by both hydrophobic and hydrophilic domains with a different degree of accessibility to employed chemicals. Besides basic features, the chemical targeting approaches can disclose information useful for pharmacological applications as well. An eminent example of this picture is the histidine/large amino acid transporter SLC7A5, known as LAT1 (Large Amino Acid Transporter 1). This protein is crucial in cell life because it is responsible for mediating the absorption and distribution of essential amino acids in peculiar body districts, such as the blood brain barrier and placenta. Furthermore, LAT1 can recognize a large variety of molecules of pharmacological interest and is also considered a hot target for drugs due to its over-expression in virtually all human cancers. Therefore, it is not surprising that the chemical targeting approach, coupled with bioinformatics, site-directed mutagenesis and transport assays, proved fundamental in describing features of LAT1 such as the substrate binding site, regulatory domains and interactions with drugs that will be discussed in this review. The results on LAT1 can be considered to have general applicability to other transporters linked with human diseases.

scholarly journals The L-Type Amino Acid Transporter LAT1—An Emerging Target in Cancer

2019 ◽  
Vol 20 (10) ◽  
pp. 2428 ◽  
Author(s):  
Pascal Häfliger ◽  
Roch-Philippe Charles
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Cancer Cells ◽  
Cell Mass ◽  
Essential Amino Acids ◽  
Amino Acid Transporter ◽  
Membrane Transporters ◽  
Preclinical Studies ◽  
Acid Transporter

Chronic proliferation is a major hallmark of tumor cells. Rapidly proliferating cancer cells are highly dependent on nutrients in order to duplicate their cell mass during each cell division. In particular, essential amino acids are indispensable for proliferating cancer cells. Their uptake across the cell membrane is tightly controlled by membrane transporters. Among those, the L-type amino acid transporter LAT1 (SLC7A5) has been repeatedly found overexpressed in a vast variety of cancers. In this review, we summarize the most recent advances in our understanding of the role of LAT1 in cancer and highlight preclinical studies and drug developments underlying the potential of LAT1 as therapeutic target.

scholarly journals Intestinal peptidases form functional complexes with the neutral amino acid transporter B0AT1

2012 ◽  
Vol 446 (1) ◽  
pp. 135-148 ◽  
Author(s):  
Stephen J. Fairweather ◽  
Angelika Bröer ◽  
Megan L. O'Mara ◽  
Stefan Bröer
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Amino Acid Transporter ◽  
The Body ◽  
Site Directed Mutagenesis ◽  
Substrate Affinity ◽  
Xenopus Laevis Oocytes ◽  
Acid Transporter

The brush-border membrane of the small intestine and kidney proximal tubule are the major sites for the absorption and re-absorption of nutrients in the body respectively. Transport of amino acids is mediated through the action of numerous secondary active transporters. In the mouse, neutral amino acids are transported by B0AT1 [broad neutral (0) amino acid transporter 1; SLC6A19 (solute carrier family 6 member 19)] in the intestine and by B0AT1 and B0AT3 (SLC6A18) in the kidney. Immunoprecipitation and Blue native electrophoresis of intestinal brush-border membrane proteins revealed that B0AT1 forms complexes with two peptidases, APN (aminopeptidase N/CD13) and ACE2 (angiotensin-converting enzyme 2). Physiological characterization of B0AT1 expressed together with these peptidases in Xenopus laevis oocytes revealed that APN increased the substrate affinity of the transporter up to 2.5-fold and also increased its surface expression (Vmax). Peptide competition experiments, in silico modelling and site-directed mutagenesis of APN suggest that the catalytic site of the peptidase is involved in the observed changes of B0AT1 apparent substrate affinity, possibly by increasing the local substrate concentration. These results provide evidence for the existence of B0AT1-containing digestive complexes in the brush-border membrane, interacting differentially with various peptidases, and responding to the dynamic needs of nutrient absorption in the intestine and kidney.

scholarly journals Ubiquitylation and endocytosis of the human LAT1/SLC7A5 amino acid transporter

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Céline Barthelemy ◽  
Bruno André
Keyword(s):  
Amino Acids ◽  
Plasma Membrane ◽  
Protein Kinase C ◽  
Amino Acid ◽  
Ubiquitin Ligase ◽  
Essential Amino Acids ◽  
Amino Acid Transporter ◽  
Kinase C ◽  
Acid Transporter ◽  
Mtorc1 Activation

AbstractThe human L-type amino acid transporter 1 (LAT1), also known as SLC7A5, catalyzes the transport of large neutral amino acids across the plasma membrane. As the main transporter of several essential amino acids, notably leucine, LAT1 plays an important role in mTORC1 activation. Furthermore, it is overexpressed in various types of cancer cells, where it contributes importantly to sustained growth. Despite the importance of LAT1 in normal and tumor cells, little is known about the mechanisms that might control its activity, for example by promoting its downregulation via endocytosis. Here we report that in HeLa cells, activation of protein kinase C by phorbol 12-myristate 13-acetate (PMA) triggers efficient endocytosis and degradation of LAT1. Under these conditions we found LAT1 downregulation to correlate with increased LAT1 ubiquitylation. This modification was considerably reduced in cells depleted of the Nedd4-2 ubiquitin ligase. By systematically mutagenizing the residues of the LAT1 cytosolic tails, we identified a group of three close lysines (K19, K25, K30) in the N-terminal tail that are important for PMA-induced ubiquitylation and downregulation. Our study thus unravels a mechanism of induced endocytosis of LAT1 elicited by Nedd4-2-mediated ubiquitylation of the transporter’s N-terminal tail.

A novel role of the C-terminus of b0,+AT in the ER–Golgi trafficking of the rBAT–b0,+AT heterodimeric amino acid transporter

2008 ◽  
Vol 417 (2) ◽  
pp. 441-448 ◽  
Author(s):  
Shinichi Sakamoto ◽  
Arthit Chairoungdua ◽  
Shushi Nagamori ◽  
Pattama Wiriyasermkul ◽  
Kanyarat Promchan ◽  
...  
Keyword(s):  
Amino Acid ◽  
Light Chain ◽  
Amino Acid Transporter ◽  
Site Directed Mutagenesis ◽  
Amino Acid Transporters ◽  
Hek 293 ◽  
C Terminus ◽  
Heterodimeric Complex ◽  
Acid Transporter ◽  
Membrane Spanning

The heterodimeric complex composed of rBAT (related to b0,+ amino acid transporter), a single-membrane-spanning glycosylated heavy chain, and b0,+AT, a putative 12-membrane-spanning non-glycosylated light chain, is an amino acid transporter that mediates the activity of system b0,+, a major apical transport system for cystine and dibasic amino acids in renal proximal tubule and small intestine. The C-terminus of b0,+AT has been proposed to play an important role in the functional expression of the heterodimeric transporters. In the present study, to reveal the roles of the C-terminus, we analysed b0,+AT mutants whose C-termini were sequentially deleted or replaced by site-directed mutagenesis in polarized MDCKII (Madin–Darby canine kidney II), non-polarized HEK-293 (human embryonic kidney-293) and HeLa cells. Although the deletion of C-terminus of b0,+AT did not affect the formation of a heterodimer with rBAT, it resulted in the loss of apparent transport function, owing to the failure of the plasma-membrane targeting of rBAT–b0,+AT heterodimeric complex associated with incomplete glycosylation of rBAT. A motif-like sequence Val480-Pro481-Pro482 was identified in the C-terminus of b0,+AT to be responsible for the C-terminus action in promoting the trafficking of rBAT–b0,+AT heterodimeric complex from the ER (endoplasmic reticulum) to Golgi apparatus. This is, to our knowledge, the first demonstration of the active contribution of the C-terminus of a light-chain subunit to the intracellular trafficking of heterodimeric transporters. Because the motif-like sequence Val480-Pro481-Pro482 is well conserved among the C-termini of light-chain subunits, common regulatory mechanisms could be proposed among heterodimeric amino acid transporters.

scholarly journals Proximal-type epithelioid sarcoma in pubic region expressing L-type amino acid transporter 1: A case report

2022 ◽  
Vol 10 ◽  
pp. 2050313X2110679
Author(s):  
Shunsuke Yahiro ◽  
Takuya Fujimoto ◽  
Ikuo Fujita ◽  
Toshihiro Takai ◽  
Toshiko Sakuma ◽  
...  
Keyword(s):  
Amino Acid ◽  
Malignant Tumors ◽  
Epithelioid Sarcoma ◽  
Essential Amino Acids ◽  
Amino Acid Transporter ◽  
Soft Tissue Neoplasm ◽  
Boron Neutron Capture ◽  
Acid Transporter ◽  
Early Tumor ◽  
The Right

Proximal-type epithelioid sarcoma is an aggressive malignant soft-tissue neoplasm, a “proximal” variant of epithelioid sarcoma, resistant to multimodal therapy and involved in early tumor-related death. Pertinent treatments are, therefore, continually being explored. A 24-year-old woman with nonmetastatic proximal-type epithelioid sarcoma, originating subcutaneously on the right side of the vulva, underwent surgical resection; the lesion recurred, however, leading to death 3 months after the second surgery. Here described is a case of proximal-type epithelioid sarcoma expressing L-type amino acid transporter 1 (LAT1) that transports essential amino acids and p-borono-L-phenylalanine (BPA)—the chemical compound used in boron neutron capture therapy (BNCT)—and is highly expressed in many malignant tumors. Recently, LAT1 has drawn attention, and relevant treatments have been studied—LAT1 inhibitor and BNCT. LAT1 expression in proximal-type epithelioid sarcoma may lead to cogent treatments for the disease.

scholarly journals The Regulation and Function of the L-Type Amino Acid Transporter 1 (LAT1) in Cancer

2018 ◽  
Vol 19 (8) ◽  
pp. 2373 ◽  
Author(s):  
Travis Salisbury ◽  
Subha Arthur
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Cancer Cells ◽  
Amino Acid Uptake ◽  
Essential Amino Acids ◽  
Amino Acid Transporter ◽  
Amino Acid Transporters ◽  
Acid Uptake ◽  
Cancer Pathways ◽  
Acid Transporter

The progression of cancer is associated with increases in amino acid uptake by cancer cells. Upon their entry into cells through specific transporters, exogenous amino acids are used to synthesize proteins, nucleic acids and lipids and to generate ATP. The essential amino acid leucine is also important for maintaining cancer-associated signaling pathways. By upregulating amino acid transporters, cancer cells gain greater access to exogenous amino acids to support chronic proliferation, maintain metabolic pathways, and to enhance certain signal transduction pathways. Suppressing cancer growth by targeting amino acid transporters will require an in-depth understanding of how cancer cells acquire amino acids, in particular, the transporters involved and which cancer pathways are most sensitive to amino acid deprivation. L-Type Amino Acid Transporter 1 (LAT1) mediates the uptake of essential amino acids and its expression is upregulated during the progression of several cancers. We will review the upstream regulators of LAT1 and the downstream effects caused by the overexpression of LAT1 in cancer cells.

scholarly journals Bed rest impairs skeletal muscle amino acid transporter expression, mTORC1 signaling, and protein synthesis in response to essential amino acids in older adults

2012 ◽  
Vol 302 (9) ◽  
pp. E1113-E1122 ◽  
Author(s):  
Micah J. Drummond ◽  
Jared M. Dickinson ◽  
Christopher S. Fry ◽  
Dillon K. Walker ◽  
David M. Gundermann ◽  
...  
Keyword(s):  
Older Adults ◽  
Amino Acid ◽  
Protein Content ◽  
Bed Rest ◽  
Essential Amino Acids ◽  
Amino Acid Transporter ◽  
Transporter Protein ◽  
Mtorc1 Signaling ◽  
Acid Transporter ◽  
Transporter Expression

Skeletal muscle atrophy during bed rest is attributed, at least in part, to slower basal muscle protein synthesis (MPS). Essential amino acids (EAA) stimulate mammalian target of rapamycin (mTORC1) signaling, amino acid transporter expression, and MPS and are necessary for muscle mass maintenance, but there are no data on the effect of inactivity on this anabolic mechanism. We hypothesized that bed rest decreases muscle mass in older adults by blunting the EAA stimulation of MPS through reduced mTORC1 signaling and amino acid transporter expression in older adults. Six healthy older adults (67 ± 2 yr) participated in a 7-day bed rest study. We used stable isotope tracers, Western blotting, and real-time qPCR to determine the effect of bed rest on MPS, muscle mTORC1 signaling, and amino acid transporter expression and content in the postabsorptive state and after acute EAA ingestion. Bed rest decreased leg lean mass by ∼4% ( P < 0.05) and increased postabsorptive mTOR protein ( P < 0.05) levels while postabsorptive MPS was unchanged ( P > 0.05). Before bed rest acute EAA ingestion increased MPS, mTOR (Ser2448), S6 kinase 1 (Thr389, Thr421/Ser424), and ribosomal protein S6 (Ser240/244) phosphorylation, activating transcription factor 4, L-type amino acid transporter 1 and sodium-coupled amino acid transporter 2 protein content ( P < 0.05). However, bed rest blunted the EAA-induced increase in MPS, mTORC1 signaling, and amino acid transporter protein content. We conclude that bed rest in older adults significantly attenuated the EAA-induced increase in MPS with a mechanism involving reduced mTORC1 signaling and amino acid transporter protein content. Together, our data suggest that a blunted EAA stimulation of MPS may contribute to muscle loss with inactivity in older persons.

Sign in / Sign up

Export Citation Format

Share Document