Identification and Characterization of a Membrane Protein (y+L Amino Acid Transporter-1) That Associates with 4F2hc to Encode the Amino Acid Transport Activity y+L

doi:10.1074/jbc.273.49.32437

Identification and Characterization of a Membrane Protein (y⁺L Amino Acid Transporter-1) That Associates with 4F2hc to Encode the Amino Acid Transport Activity y⁺L

A CANDIDATE GENE FOR LYSINURIC PROTEIN INTOLERANCE*

From the Departament de Bioquı́mica i Biologia Molecular and the ^‖Departament de Fisiologia (Immunologia), Facultat de Biologia, Universitat de Barcelona, Avda. Diagonal 645, 08028 Barcelona, Spain and the ^**Laboratory of Molecular Embryology NICHD, National Institutes of Health, Bethesda, Maryland 20892-5431

Abstract

We have identified a new human cDNA (y⁺L amino acid transporter-1 (y⁺LAT-1)) that induces system y⁺L transport activity with 4F2hc (the surface antigen 4F2 heavy chain) in oocytes. Human y⁺LAT-1 is a new member of a family of polytopic transmembrane proteins that are homologous to the yeast high affinity methionine permease MUP1. Other members of this family, theXenopus laevis IU12 and the human KIAA0245 cDNAs, also co-express amino acid transport activity with 4F2hc in oocytes, with characteristics that are compatible with those of systems L and y⁺L, respectively. y⁺LAT-1 protein forms a ≈135-kDa, disulfide bond-dependent heterodimer with 4F2hc in oocytes, which upon reduction results in two protein bands of ≈85 kDa (i.e. 4F2hc) and ≈40 kDa (y⁺LAT-1). Mutation of the human 4F2hc residue cysteine 109 (Cys-109) to serine abolishes the formation of this heterodimer and drastically reduces the co-expressed transport activity. These data suggest that y⁺LAT-1 and other members of this family are different 4F2 light chain subunits, which associated with 4F2hc, constitute different amino acid transporters. Human y⁺LAT-1 mRNA is expressed in kidney ≫ peripheral blood leukocytes ≫ lung > placenta = spleen > small intestine. The humany⁺LAT-1 gene localizes at chromosome 14q11.2 (17cR ≈ 374 kb from D14S1350), within the lysinuric protein intolerance (LPI) locus (Lauteala, T., Sistonen, P., Savontaus, M. L., Mykkanen, J., Simell, J., Lukkarinen, M., Simmell, O., and Aula, P. (1997) Am. J. Hum. Genet. 60, 1479–1486). LPI is an inherited autosomal disease characterized by a defective dibasic amino acid transport in kidney, intestine, and other tissues. The pattern of expression of human y⁺LAT-1, its co-expressed transport activity with 4F2hc, and its chromosomal location within the LPI locus, suggest y⁺LAT-1 as a candidate gene for LPI.

Footnotes

↵* This research was supported in part by EU BIOMED 2 Grant PL963514, Dirección General de Investigación Cientı́fica y Técnica Research Grants PM96/0060, and Generalitat de Catalunya (Spain) Grant 1997 SGR 121.The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

The nucleotide sequence(s) reported in this paper has been submitted to the GenBank™/EMBL Data Bank with accession number(s) .
↵‡ These two authors contributed equally to this work.
↵§ Recipients of a grant from the Ministerio de Educación y Cultura.
↵¶ Recipients of a grant from the ComissióInterdepartamental de Recerca i Tecnologia.
↵‡ To whom correspondence should be addressed. Tel.: 34-93-4021543; Fax: 34-93-4021559.
↵1 F. Verrey, personal communication.
↵3 M. Pineda, R. Estévez, and M. Palacı́n, manuscript in preparation.
↵4 R. Estévez and M. Palacı́n, unpublished results.
↵5 M. Pineda, D. Torrents, and M. Palacı́n, unpublished observations.
Abbreviations:

CAT

cationic amino acid transporter

LAT

L amino acid transporter

LPI

lysinuric protein intolerance

IMAGE

Integrated and Molecular Analysis of Genomes and their Expression

SHGC

Stanford Human Genome Center

PCR

polymerase chain reaction

bp

base pair(s).
- Received August 7, 1998.
- Revision received September 18, 1998.
The American Society for Biochemistry and Molecular Biology, Inc.