Effects of ecotropic murine retroviruses on the dual-function cell surface receptor/basic amino acid transporter.

ABSTRACT The type D simian retroviruses cause immunosuppression in macaques and have been reported as a presumptive opportunistic infection in a patient with AIDS. Previous evidence based on viral interference has strongly suggested that the type D simian viruses share a common but unknown cell surface receptor with three type C viruses: feline endogenous virus (RD114), baboon endogenous virus, and avian reticuloendotheliosis virus. Furthermore, the receptor gene for these viruses has been mapped to human chromosome 19q13.1–13.2. We now report the isolation and characterization of a cell surface receptor for this group of retroviruses by using a human T-lymphocyte cDNA library in a retroviral vector. Swiss mouse fibroblasts (NIH 3T3), which are naturally resistant to RD114, were transduced with the retroviral library and then challenged with an RD114-pseudotyped virus containing a dominant selectable gene for puromycin resistance. Puromycin selection yielded 12 cellular clones that were highly susceptible to a β-galactosidase-encoding lacZ(RD114) pseudotype virus. Using PCR primers specific for vector sequences, we amplified a common 2.9-kb product from 10 positive clones. Expression of the 2.9-kb cDNA in Chinese hamster ovary cells conferred susceptibility to RD114, baboon endogenous virus, and the type D simian retroviruses. The 2.9-kb cDNA predicted a protein of 541 amino acids that had 98% identity with the previously cloned human Na+-dependent neutral-amino-acid transporter Bo. Accordingly, expression of the RD114 receptor in NIH 3T3 cells resulted in enhanced cellular uptake of l-[3H]alanine andl-[3H]glutamine. RNA blot (Northern) analysis suggested that the RD114 receptor is widely expressed in human tissues and cell lines, including hematopoietic cells. The human Botransporter gene has been previously mapped to 19q13.3, which is closely linked to the gene locus of the RD114 receptor.

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Multiple components of arginine and phenylalanine transport induced in neutral and basic amino acid transporter-cRNA-injected Xenopus oocytes

Biochemical Journal ◽

10.1042/bj3180915 ◽

1996 ◽

Vol 318 (3) ◽

pp. 915-922 ◽

Cited By ~ 13

Author(s):

George J PETER ◽

Iain G. DAVIDSON ◽

Aamir AHMED ◽

Lynn McILROY ◽

Alexander R. FORRESTER ◽

...

Keyword(s):

Amino Acid ◽

Xenopus Oocytes ◽

Competitive Inhibition ◽

Protein Complexes ◽

Basic Amino Acid ◽

Amino Acid Transporter ◽

Transport Processes ◽

Arginine Transport ◽

Acid Transporter ◽

Phenylalanine Transport

The induced uptakes of l-[3H]phenylalanine and l-[3H]arginine in oocytes injected with clonal NBAT (neutral and basic amino acid transporter) cRNA show differential inactivation by pre-treatment with N-ethylmaleimide (NEM), revealing at least two distinct transport processes. NEM-resistant arginine transport is inhibited by leucine and phenylalanine but not by alanine or valine; mutual competitive inhibition of NEM-resistant uptake of arginine and phenylalanine indicates that the two amino acids share a single transporter. NEM-senstive arginine transport is inhibited by leucine, phenylalanine, alanine and valine. At least two NEM-sensitive transporters may be expressed because we have been unable to confirm mutual competitive inhibition between arginine and phenylalanine transport. The NEM-resistant transport mechanism appears to involve distinct but overlapping binding sites for cationic and zwitterionic substrates. NBAT is known to form oligomeric protein complexes in cell membranes, and its functional roles when expressed in Xenopus oocytes may include interaction with oocyte proteins, leading to increased native amino acid transport activities; these resemble NBAT-expressed activities in terms of NEM-sensitivity and apparent substrate range (including an unusual inhibition by β-phenylalanine).

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Characterization of the rat neutral and basic amino acid transporter utilizing anti-peptide antibodies.

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.90.9.4022 ◽

1993 ◽

Vol 90 (9) ◽

pp. 4022-4026 ◽

Cited By ~ 18

Author(s):

R. Mosckovitz ◽

N. Yan ◽

E. Heimer ◽

A. Felix ◽

S. S. Tate ◽

...

Keyword(s):

Amino Acid ◽

Basic Amino Acid ◽

Amino Acid Transporter ◽

Acid Transporter ◽

Peptide Antibodies

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Galectin-lattice sustains function of cationic amino acid transporter and insulin secretion of pancreatic β cells

The Journal of Biochemistry ◽

10.1093/jb/mvaa007 ◽

2020 ◽

Vol 167 (6) ◽

pp. 587-596 ◽

Cited By ~ 1

Author(s):

Kento Maeda ◽

Masayoshi Tasaki ◽

Yukio Ando ◽

Kazuaki Ohtsubo

Keyword(s):

Insulin Secretion ◽

Amino Acid ◽

Cell Surface ◽

Amino Acid Transporter ◽

Cell Surface Expression ◽

Cationic Amino Acid Transporter ◽

Β Cells ◽

Pancreatic Β Cells ◽

Cationic Amino Acid ◽

Acid Transporter

Abstract Maintenance of cell surface residency and function of glycoproteins by lectins are essential for regulating cellular functions. Galectins are β-galactoside-binding lectins and form a galectin-lattice, which regulates stability, clustering, membrane sub-domain localization and endocytosis of plasmalemmal glycoproteins. We have previously reported that galectin-2 (Gal-2) forms a complex with cationic amino acid transporter 3 (CAT3) in pancreatic β cells, although the biological significance of the molecular interaction between Gal-2 and CAT3 has not been elucidated. In this study, we demonstrated that the structure of N-glycan of CAT3 was either tetra- or tri-antennary branch structure carrying β-galactosides, which works as galectin-ligands. Indeed, CAT3 bound to Gal-2 using β-galactoside epitope. Moreover, the disruption of the glycan-mediated bindings between galectins and CAT3 significantly reduced cell surface expression levels of CAT3. The reduced cell surface residency of CAT3 attenuated the cellular arginine uptake activities and subsequently reduced nitric oxide production, and thus impaired the arginine-stimulated insulin secretion of pancreatic β cells. These results indicate that galectin-lattice stabilizes CAT3 by preventing endocytosis to sustain the arginine-stimulated insulin secretion of pancreatic β cells. This provides a novel cell biological insight into the endocrinological mechanism of nutrition metabolism and homeostasis.

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