4F2 (CD98) Heavy Chain Is Associated Covalently with an Amino Acid Transporter and Controls Intracellular Trafficking and Membrane Topology of 4F2 Heterodimer*
- Eijiro Nakamura‡§,
- Masaki Sato‡§,
- Hailin Yang‡,
- Fumi Miyagawa‡,
- Masashi Harasaki‡,
- Koichi Tomita‡,
- Satoshi Matsuoka¶,
- Akinori Noma¶,
- Kazuhiro Iwai‡ and
- Nagahiro Minato‡‖
- From the Departments of ‡Immunology and Cell Biology and ¶Physiology, Graduate School of Medicine, Kyoto University, Kyoto 606-8501, Japan
Abstract
4F2, also termed CD98, is an integral membrane protein consisting of a heavy chain linked to a light chain by disulfide bond. We have generated a monoclonal antibody to the mouse 4F2 light chain and cloned the cDNA. It encodes a mouse counterpart of rat L-type amino acid transporter-1, and induces system L amino acid transport in Xenopus oocytes in the presence of 4F2 heavy chain. Transfection studies in mammalian cells have indicated that the 4F2 heavy chain is expressed on the plasma membrane on its own, whereas the 4F2 light chain can be transported to the surface only in the presence of 4F2 heavy chain. 4F2 heavy chain is expressed diffusely on the surface of fibroblastic L cells, whereas it is localized selectively to the cell-cell adhesion sites in L cells expressing cadherins. These results indicate that the 4F2 heavy chain is associated covalently with an amino acid transporter and controls the cell surface expression as well as the membrane topology of the 4F2 heterodimer. Although 4F2 heavy and light chains are expressed coordinately in most tissues, the light chain is barely detected by the antibody in kidney and intestine, despite the presence of heavy chain in a complex form. The results predict the presence of multiple 4F2 light chains.
Footnotes
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↵* This work was supported by grants from the Ministry of Education and Science, Japanese Government.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) AB17189.
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↵§ The first two authors equally contributed to the work.
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↵‖ To whom correspondence should be addressed: Dept. of Immunology and Cell Biology, Faculty of Medicine, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan. Tel.: 81-75-753-4659; Fax: 81-75-753-4403; E-mail: minato{at}med.kyoto-u.ac.jp.
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↵2 K. Iwai, unpublished data.
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↵3 H. Yang and N. Minato, unpublished observations.
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↵4 K. Suga and N. Minato, unpublished observations.
- Abbreviations:
- H-chain
-
heavy chain
- L-chain
-
light chain
- ABC
-
avidin-biotin complex
- BAT
-
broad specificity amino acid transporter
- ER
-
endoplasmic reticulum
- FITC
-
fluorescein isothiocyanate
- LAT1
-
L-type amino acid transporter 1
- mAb
-
monoclonal antibody
- EL
-
L cells stably transfected with E-cadherin
- NL
-
L cells transfected with N-cadherin
- PAGE
-
polyacrylamide gel electrophoresis
- TBS
-
Tris-buffered saline.
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- Received September 21, 1998.
- Revision received October 27, 1998.
- The American Society for Biochemistry and Molecular Biology, Inc.
