Key points are not available for this paper at this time.
CD98 is a cell surface heterodimer formed by the covalent linkage of CD98 heavy chain (CD98hc) with several different light chains to form amino acid transporters. CD98hc also binds specifically to the integrin β1A cytoplasmic domain and regulates integrin function. In this study, we examined the relationship between the ability of CD98hc to stimulate amino acid transport and to affect integrin function. By constructing chimeras with CD98hc and a type II transmembrane protein (CD69), we found that the cytoplasmic and transmembrane domains of CD98hc are required for its effects on integrin function, while the extracellular domain is required for stimulation of isoleucine transport. Consequently, the capacity to promote amino acid transport is not required for CD98hc's effect on integrin function. Furthermore, a mutant of CD98hc that lacks its integrin binding site can still promote increased isoleucine transport. Thus, these two functions of CD98hc are separable and require distinct domains of the protein. CD98 is a cell surface heterodimer formed by the covalent linkage of CD98 heavy chain (CD98hc) with several different light chains to form amino acid transporters. CD98hc also binds specifically to the integrin β1A cytoplasmic domain and regulates integrin function. In this study, we examined the relationship between the ability of CD98hc to stimulate amino acid transport and to affect integrin function. By constructing chimeras with CD98hc and a type II transmembrane protein (CD69), we found that the cytoplasmic and transmembrane domains of CD98hc are required for its effects on integrin function, while the extracellular domain is required for stimulation of isoleucine transport. Consequently, the capacity to promote amino acid transport is not required for CD98hc's effect on integrin function. Furthermore, a mutant of CD98hc that lacks its integrin binding site can still promote increased isoleucine transport. Thus, these two functions of CD98hc are separable and require distinct domains of the protein. complement dominant suppression Chinese hamster ovary 1,4-piperazinediethanesulfonic acid polyacrylamide gel electrophoresis activation index Hanks' buffered salt solution CD98hc is a widely distributed transmembrane protein that was originally discovered as a T-cell activation antigen (1Haynes B.F. Hemler M.E. Mann D.L. Eisenbarth G.S. Shelhamer J. Mostowski H.S. Thomas C.A. Strominger J.L. Fauci A.S. J. Immunol. 1981; 126: 1409-1414PubMed Google Scholar). CD98hc expression is tightly linked to cell proliferation, and antibodies against CD98hc can inhibit cell growth or induce apoptosis in specific cell types (2Yagita H. Masuko T. Hashimoto Y. Cancer Res. 1986; 46: 1478-1484PubMed Google Scholar, 3Warren A.P. Patel K. McConkey D.J. Palacios R. Blood. 1996; 87: 3676-3687Crossref PubMed Google Scholar). A compelling body of evidence implicates CD98hc in the transport of amino acids. CD98hc overexpression stimulates multiple amino acid transport systems including L, y+L, and xc− (4Verrey F. Meier C. Rossier G. Kuhn L.C. Pfluegers Arch. 2000; 440: 503-512Crossref PubMed Google Scholar). Furthermore, mutations in its closest paralogue, D2 (r-BAT), lead to a disorder of cysteine transport (5Calonge M.J. Gasparini P. Chillaron J. Chillon M. Gallucci M. Rousaud F. Zelante L. Testar X. Dallapiccola B. Di Silverio F. Nat. Genet. 1994; 6: 420-425Crossref PubMed Scopus (344) Google Scholar). Structurally, CD98 is a disulfide-bonded heterodimer of a common ∼80-kDa heavy chain (CD98hc) with one of several ∼40-kDa light chains. Because these light chains have multiple membrane-spanning domains, they resemble permeases and are believed to provide the amino acid transport activity of CD98 (6Mastroberardino L. Spindler B. Pfeiffer R. Skelly P.J. Loffing J. Shoemaker C.B. Verrey F. Nature. 1998; 395: 288-291Crossref PubMed Scopus (456) Google Scholar, 7Torrents D. Estevez R.A. Pineda M. Fernandez E. Lloberas J. Yun-Bo S. Zorzano A. Palacin M. J. Biol. Chem. 1998; 273: 32437-32445Abstract Full Text Full Text PDF PubMed Scopus (293) Google Scholar, 8Kanai Y. Segawa H. Miyamoto K. Uchino H. Takeda E. Endou H. J. Biol. Chem. 1998; 273: 23629-23632Abstract Full Text Full Text PDF PubMed Scopus (871) Google Scholar). CD98hc may act to regulate the expression and cellular localization of the amino acid transporting activity of the light chain (6Mastroberardino L. Spindler B. Pfeiffer R. Skelly P.J. Loffing J. Shoemaker C.B. Verrey F. Nature. 1998; 395: 288-291Crossref PubMed Scopus (456) Google Scholar, 9Nakamura E. Sato M. Yang H. Miyagawa F. Harasaki M. Tomita K. Matsuoka S. Noma A. Iwai K. Minato N. J. Biol. Chem. 1999; 274: 3009-3016Abstract Full Text Full Text PDF PubMed Scopus (230) Google Scholar). Thus, this widely distributed membrane protein is strongly implicated in amino acid transport.There is also a growing literature implicating CD98hc in integrin function. Integrins are heterodimeric adhesion receptors expressed in almost every multicellular animal cell type (10Hynes R.O. Cell. 1992; 69: 11-25Abstract Full Text PDF PubMed Scopus (8966) Google Scholar). Cells can rapidly modulate their integrins' affinity for extracellular ligands (activation), thereby regulating multiple integrin-dependent functions (11Hughes P.E. Pfaff M. Trends Cell Biol. 1998; 8: 359-364Abstract Full Text Full Text PDF PubMed Scopus (380) Google Scholar). Integrin activation is inhibited by overexpression of isolated β1A integrin cytoplasmic domains (dominant suppression) (12Chen Y.-P. O'Toole T.E. Shipley T. Forsyth J. LaFlamme S.E. Yamada K.M. Shattil S.J. Ginsberg M.H. J. Biol. Chem. 1994; 269: 18307-18310Abstract Full Text PDF PubMed Google Scholar). CD98hc was identified as an integrin regulator in an expression-cloning scheme for proteins that can complement dominant suppression (CODS)1 (13Fenczik C.A. Sethi T. Ramos J.W. Hughes P.E. Ginsberg M.H. Nature. 1997; 390: 81-85Crossref PubMed Scopus (254) Google Scholar). In addition, CD98hc binds to integrin β1A cytoplasmic domains, and this interaction correlates with CODS (14Zent R. Fenczik C.A. Calderwood D.A. Liu S. Dellos M. Ginsberg M.H. J. Biol. Chem. 2000; 275: 5059-5064Abstract Full Text Full Text PDF PubMed Scopus (94) Google Scholar). Furthermore, clustering CD98hc activates multiple integrin-dependent functions (13Fenczik C.A. Sethi T. Ramos J.W. Hughes P.E. Ginsberg M.H. Nature. 1997; 390: 81-85Crossref PubMed Scopus (254) Google Scholar,15Ohta H. Tsurudome M. Matsumura H. Koga Y. Morikawa S. Kawano M. Kusugawa S. Komada H. Nishio M. Ito Y. EMBO J. 1994; 13: 2044-2055Crossref PubMed Scopus (75) Google Scholar, 16Chandrasekaran S. Guo N.H. Rodrigues R.G. Kaiser J. Roberts D.D. J. Biol. Chem. 1999; 274: 11408-11416Abstract Full Text Full Text PDF PubMed Scopus (111) Google Scholar) and mimics β1 integrin cosignaling in T-cells (17Warren A.P. Patel K. Miyamoto Y. Wygant J.N. Woodside D.G. McIntyre B.W. Immunology. 2000; 99: 62-68Crossref PubMed Scopus (27) Google Scholar). Thus, CD98hc physically and functionally interacts with integrin adhesion receptors. Indeed, clustering of CD98hc can stimulate several classes of integrins in multiple cell types (13Fenczik C.A. Sethi T. Ramos J.W. Hughes P.E. Ginsberg M.H. Nature. 1997; 390: 81-85Crossref PubMed Scopus (254) Google Scholar, 15Ohta H. Tsurudome M. Matsumura H. Koga Y. Morikawa S. Kawano M. Kusugawa S. Komada H. Nishio M. Ito Y. EMBO J. 1994; 13: 2044-2055Crossref PubMed Scopus (75) Google Scholar, 16Chandrasekaran S. Guo N.H. Rodrigues R.G. Kaiser J. Roberts D.D. J. Biol. Chem. 1999; 274: 11408-11416Abstract Full Text Full Text PDF PubMed Scopus (111) Google Scholar).In the present study, we have assessed the relationship between the amino acid transport and integrin regulatory activities of CD98hc. We found that the CD98hc alone is necessary and sufficient for the interaction of CD98 with the β1A integrin tail and for CODS. By forming chimeras between CD98hc and another type II transmembrane protein, we found that the cytoplasmic and transmembrane domains of CD98hc are required for integrin interactions but not for stimulation of isoleucine transport. In contrast, the CD98hc extracellular domain was required for stimulation of amino acid transport. Thus, the amino acid transport activity and integrin interactions of CD98 are independent activities of the protein and are mediated by different domains of CD98hc.DISCUSSIONCD98hc combines with several different light chains to form a series of heterodimers that are involved in amino acid transport. CD98hc binds to integrin β1A cytoplasmic domains and blocks the capacity of β1A cytoplasmic domains to suppress integrin activation (CODS). We have compared the structural requirements of CD98hc for interaction with integrins with those involved in regulation of amino acid transport. Here we report that: 1) mutation of cysteines that disrupt CD98 heavy-light chain and amino acid transport not disrupt its binding to β1A or its effect on integrin cytoplasmic and transmembrane domains of CD98hc to another type II transmembrane protein are necessary and sufficient for binding to the integrin β1A tail and for CODS. to stimulate amino acid transport. of the cytoplasmic or transmembrane domains of CD98hc with those of the capacity of CD98hc to to β1A and regulate integrin but effects on the amino acid transport of Thus, the amino acid transport of CD98 is not required for its effects on integrin function, and amino acid transport can in the of of a covalent CD98 heterodimer is not required for its effects on integrin function. CD98hc two extracellular cysteines and is the transmembrane domain of CD98hc and in a with a cysteine in an extracellular of the light chain between transmembrane domains and R. Spindler B. Loffing J. Skelly P.J. Shoemaker C.B. Verrey F. 1998; PubMed Scopus Google Scholar). of and the covalent with the light chain but not interactions with or effects on the covalent was is that was still a Indeed, Pfeiffer R. Spindler B. Loffing J. Skelly P.J. Shoemaker C.B. Verrey F. 1998; PubMed Scopus Google Scholar) that the mutant still the surface expression of the light mutation still the transport as the a we also found that heavy chains also to the β1A Furthermore, of the light chain increased of heterodimers and amino acid transport but not integrin interactions or Consequently, that the covalent of CD98hc with a light chain is not required for its interaction with integrins or for the regulation of cytoplasmic and transmembrane domains of CD98hc are necessary and sufficient for binding to the integrin β1A tail and for effects on integrin function. of these domains was integrin interactions effects on integrins to by of these two is the of the CD98hc transmembrane domain in binding to the β1A cytoplasmic is that the CD98hc transmembrane domain the of the cytoplasmic domain to promote binding to integrin cytoplasmic integrin cytoplasmic domain protein was on that the in the have that β1A of the domain may in the membrane A. G. S. J. Biol. Chem. 1999; 274: Full Text Full Text PDF PubMed Scopus Google Scholar). Consequently, the CD98hc transmembrane domain may with a transmembrane of protein Furthermore, as and also the membrane S. Calderwood D.A. Ginsberg M.H. J. Cell 2000; PubMed Google Scholar). Thus, the localization of this in the membrane may binding of the CD98hc with proteins the transmembrane to the tail In provide the of a specific for the cytoplasmic and transmembrane domains of interaction with and regulation of β1A integrin of amino acid transport and integrins by CD98hc is a distinct and separable of the in the cytoplasmic or transmembrane domains of CD98hc with those of the capacity to to β1A and regulate integrin In contrast, these effect on the amino acid transport of the of the extracellular domain of CD98hc with that of in a protein that was still of integrin but not stimulate isoleucine transport. Thus, the amino acid transport activity of CD98hc is not required for its effect on integrin functions as a to the light chains and to the membrane F. D.L. M.H. Pfeiffer R. J. Biol. 1999; PubMed Scopus Google Scholar, M. J. Zorzano A. 2000; PubMed Scopus Google Scholar). We found that the interaction of CD98hc with integrins and amino acid are to distinct domains of the protein and are not adhesion to the of these receptors to the cell Consequently, the interaction may to the localization of CD98 amino acid transport. CD98hc can multiple integrin-dependent including cell T-cell and cell adhesion (13Fenczik C.A. Sethi T. Ramos J.W. Hughes P.E. Ginsberg M.H. Nature. 1997; 390: 81-85Crossref PubMed Scopus (254) Google Scholar,15Ohta H. Tsurudome M. Matsumura H. Koga Y. Morikawa S. Kawano M. Kusugawa S. Komada H. Nishio M. Ito Y. EMBO J. 1994; 13: 2044-2055Crossref PubMed Scopus (75) Google Scholar, 16Chandrasekaran S. Guo N.H. Rodrigues R.G. Kaiser J. Roberts D.D. J. Biol. Chem. 1999; 274: 11408-11416Abstract Full Text Full Text PDF PubMed Scopus (111) Google Scholar, A.P. Patel K. Miyamoto Y. Wygant J.N. Woodside D.G. McIntyre B.W. Immunology. 2000; 99: 62-68Crossref PubMed Scopus (27) Google Scholar). Thus, the can promote cell adhesion in to the activities of amino acid transporters. CD98hc is a widely distributed transmembrane protein that was originally discovered as a T-cell activation antigen (1Haynes B.F. Hemler M.E. Mann D.L. Eisenbarth G.S. Shelhamer J. Mostowski H.S. Thomas C.A. Strominger J.L. Fauci A.S. J. Immunol. 1981; 126: 1409-1414PubMed Google Scholar). CD98hc expression is tightly linked to cell proliferation, and antibodies against CD98hc can inhibit cell growth or induce apoptosis in specific cell types (2Yagita H. Masuko T. Hashimoto Y. Cancer Res. 1986; 46: 1478-1484PubMed Google Scholar, 3Warren A.P. Patel K. McConkey D.J. Palacios R. Blood. 1996; 87: 3676-3687Crossref PubMed Google Scholar). A compelling body of evidence implicates CD98hc in the transport of amino acids. CD98hc overexpression stimulates multiple amino acid transport systems including L, y+L, and xc− (4Verrey F. Meier C. Rossier G. Kuhn L.C. Pfluegers Arch. 2000; 440: 503-512Crossref PubMed Google Scholar). Furthermore, mutations in its closest paralogue, D2 (r-BAT), lead to a disorder of cysteine transport (5Calonge M.J. Gasparini P. Chillaron J. Chillon M. Gallucci M. Rousaud F. Zelante L. Testar X. Dallapiccola B. Di Silverio F. Nat. Genet. 1994; 6: 420-425Crossref PubMed Scopus (344) Google Scholar). Structurally, CD98 is a disulfide-bonded heterodimer of a common ∼80-kDa heavy chain (CD98hc) with one of several ∼40-kDa light chains. Because these light chains have multiple membrane-spanning domains, they resemble permeases and are believed to provide the amino acid transport activity of CD98 (6Mastroberardino L. Spindler B. Pfeiffer R. Skelly P.J. Loffing J. Shoemaker C.B. Verrey F. Nature. 1998; 395: 288-291Crossref PubMed Scopus (456) Google Scholar, 7Torrents D. Estevez R.A. Pineda M. Fernandez E. Lloberas J. Yun-Bo S. Zorzano A. Palacin M. J. Biol. Chem. 1998; 273: 32437-32445Abstract Full Text Full Text PDF PubMed Scopus (293) Google Scholar, 8Kanai Y. Segawa H. Miyamoto K. Uchino H. Takeda E. Endou H. J. Biol. Chem. 1998; 273: 23629-23632Abstract Full Text Full Text PDF PubMed Scopus (871) Google Scholar). CD98hc may act to regulate the expression and cellular localization of the amino acid transporting activity of the light chain (6Mastroberardino L. Spindler B. Pfeiffer R. Skelly P.J. Loffing J. Shoemaker C.B. Verrey F. Nature. 1998; 395: 288-291Crossref PubMed Scopus (456) Google Scholar, 9Nakamura E. Sato M. Yang H. Miyagawa F. Harasaki M. Tomita K. Matsuoka S. Noma A. Iwai K. Minato N. J. Biol. Chem. 1999; 274: 3009-3016Abstract Full Text Full Text PDF PubMed Scopus (230) Google Scholar). Thus, this widely distributed membrane protein is strongly implicated in amino acid transport. is also a growing literature implicating CD98hc in integrin function. Integrins are heterodimeric adhesion receptors expressed in almost every multicellular animal cell type (10Hynes R.O. Cell. 1992; 69: 11-25Abstract Full Text PDF PubMed Scopus (8966) Google Scholar). Cells can rapidly modulate their integrins' affinity for extracellular ligands (activation), thereby regulating multiple integrin-dependent functions (11Hughes P.E. Pfaff M. Trends Cell Biol. 1998; 8: 359-364Abstract Full Text Full Text PDF PubMed Scopus (380) Google Scholar). Integrin activation is inhibited by overexpression of isolated β1A integrin cytoplasmic domains (dominant suppression) (12Chen Y.-P. O'Toole T.E. Shipley T. Forsyth J. LaFlamme S.E. Yamada K.M. Shattil S.J. Ginsberg M.H. J. Biol. Chem. 1994; 269: 18307-18310Abstract Full Text PDF PubMed Google Scholar). CD98hc was identified as an integrin regulator in an expression-cloning scheme for proteins that can complement dominant suppression (CODS)1 (13Fenczik C.A. Sethi T. Ramos J.W. Hughes P.E. Ginsberg M.H. Nature. 1997; 390: 81-85Crossref PubMed Scopus (254) Google Scholar). In addition, CD98hc binds to integrin β1A cytoplasmic domains, and this interaction correlates with CODS (14Zent R. Fenczik C.A. Calderwood D.A. Liu S. Dellos M. Ginsberg M.H. J. Biol. Chem. 2000; 275: 5059-5064Abstract Full Text Full Text PDF PubMed Scopus (94) Google Scholar). Furthermore, clustering CD98hc activates multiple integrin-dependent functions (13Fenczik C.A. Sethi T. Ramos J.W. Hughes P.E. Ginsberg M.H. Nature. 1997; 390: 81-85Crossref PubMed Scopus (254) Google Scholar,15Ohta H. Tsurudome M. Matsumura H. Koga Y. Morikawa S. Kawano M. Kusugawa S. Komada H. Nishio M. Ito Y. EMBO J. 1994; 13: 2044-2055Crossref PubMed Scopus (75) Google Scholar, 16Chandrasekaran S. Guo N.H. Rodrigues R.G. Kaiser J. Roberts D.D. J. Biol. Chem. 1999; 274: 11408-11416Abstract Full Text Full Text PDF PubMed Scopus (111) Google Scholar) and mimics β1 integrin cosignaling in T-cells (17Warren A.P. Patel K. Miyamoto Y. Wygant J.N. Woodside D.G. McIntyre B.W. Immunology. 2000; 99: 62-68Crossref PubMed Scopus (27) Google Scholar). Thus, CD98hc physically and functionally interacts with integrin adhesion receptors. Indeed, clustering of CD98hc can stimulate several classes of integrins in multiple cell types (13Fenczik C.A. Sethi T. Ramos J.W. Hughes P.E. Ginsberg M.H. Nature. 1997; 390: 81-85Crossref PubMed Scopus (254) Google Scholar, 15Ohta H. Tsurudome M. Matsumura H. Koga Y. Morikawa S. Kawano M. Kusugawa S. Komada H. Nishio M. Ito Y. EMBO J. 1994; 13: 2044-2055Crossref PubMed Scopus (75) Google Scholar, 16Chandrasekaran S. Guo N.H. Rodrigues R.G. Kaiser J. Roberts D.D. J. Biol. Chem. 1999; 274: 11408-11416Abstract Full Text Full Text PDF PubMed Scopus (111) Google Scholar). In the present study, we have assessed the relationship between the amino acid transport and integrin regulatory activities of CD98hc. We found that the CD98hc alone is necessary and sufficient for the interaction of CD98 with the β1A integrin tail and for CODS. By forming chimeras between CD98hc and another type II transmembrane protein, we found that the cytoplasmic and transmembrane domains of CD98hc are required for integrin interactions but not for stimulation of isoleucine transport. In contrast, the CD98hc extracellular domain was required for stimulation of amino acid transport. Thus, the amino acid transport activity and integrin interactions of CD98 are independent activities of the protein and are mediated by different domains of CD98hc. combines with several different light chains to form a series of heterodimers that are involved in amino acid transport. CD98hc binds to integrin β1A cytoplasmic domains and blocks the capacity of β1A cytoplasmic domains to suppress integrin activation (CODS). We have compared the structural requirements of CD98hc for interaction with integrins with those involved in regulation of amino acid transport. Here we report that: 1) mutation of cysteines that disrupt CD98 heavy-light chain and amino acid transport not disrupt its binding to β1A or its effect on integrin cytoplasmic and transmembrane domains of CD98hc to another type II transmembrane protein are necessary and sufficient for binding to the integrin β1A tail and for CODS. to stimulate amino acid transport. of the cytoplasmic or transmembrane domains of CD98hc with those of the capacity of CD98hc to to β1A and regulate integrin but effects on the amino acid transport of Thus, the amino acid transport of CD98 is not required for its effects on integrin function, and amino acid transport can in the of of a covalent CD98 heterodimer is not required for its effects on integrin function. CD98hc two extracellular cysteines and is the transmembrane domain of CD98hc and in a with a cysteine in an extracellular of the light chain between transmembrane domains and R. Spindler B. Loffing J. Skelly P.J. Shoemaker C.B. Verrey F. 1998; PubMed Scopus Google Scholar). of and the covalent with the light chain but not interactions with or effects on the covalent was is that was still a Indeed, Pfeiffer R. Spindler B. Loffing J. Skelly P.J. Shoemaker C.B. Verrey F. 1998; PubMed Scopus Google Scholar) that the mutant still the surface expression of the light mutation still the transport as the a we also found that heavy chains also to the β1A Furthermore, of the light chain increased of heterodimers and amino acid transport but not integrin interactions or Consequently, that the covalent of CD98hc with a light chain is not required for its interaction with integrins or for the regulation of cytoplasmic and transmembrane domains of CD98hc are necessary and sufficient for binding to the integrin β1A tail and for effects on integrin function. of these domains was integrin interactions effects on integrins to by of these two is the of the CD98hc transmembrane domain in binding to the β1A cytoplasmic is that the CD98hc transmembrane domain the of the cytoplasmic domain to promote binding to integrin cytoplasmic integrin cytoplasmic domain protein was on that the in the have that β1A of the domain may in the membrane A. G. S. J. Biol. Chem. 1999; 274: Full Text Full Text PDF PubMed Scopus Google Scholar). Consequently, the CD98hc transmembrane domain may with a transmembrane of protein Furthermore, as and also the membrane S. Calderwood D.A. Ginsberg M.H. J. Cell 2000; PubMed Google Scholar). Thus, the localization of this in the membrane may binding of the CD98hc with proteins the transmembrane to the tail In provide the of a specific for the cytoplasmic and transmembrane domains of interaction with and regulation of β1A integrin of amino acid transport and integrins by CD98hc is a distinct and separable of the in the cytoplasmic or transmembrane domains of CD98hc with those of the capacity to to β1A and regulate integrin In contrast, these effect on the amino acid transport of the of the extracellular domain of CD98hc with that of in a protein that was still of integrin but not stimulate isoleucine transport. Thus, the amino acid transport activity of CD98hc is not required for its effect on integrin functions as a to the light chains and to the membrane F. D.L. M.H. Pfeiffer R. J. Biol. 1999; PubMed Scopus Google Scholar, M. J. Zorzano A. 2000; PubMed Scopus Google Scholar). We found that the interaction of CD98hc with integrins and amino acid are to distinct domains of the protein and are not adhesion to the of these receptors to the cell Consequently, the interaction may to the localization of CD98 amino acid transport. CD98hc can multiple integrin-dependent including cell T-cell and cell adhesion (13Fenczik C.A. Sethi T. Ramos J.W. Hughes P.E. Ginsberg M.H. Nature. 1997; 390: 81-85Crossref PubMed Scopus (254) Google Scholar,15Ohta H. Tsurudome M. Matsumura H. Koga Y. Morikawa S. Kawano M. Kusugawa S. Komada H. Nishio M. Ito Y. EMBO J. 1994; 13: 2044-2055Crossref PubMed Scopus (75) Google Scholar, 16Chandrasekaran S. Guo N.H. Rodrigues R.G. Kaiser J. Roberts D.D. J. Biol. Chem. 1999; 274: 11408-11416Abstract Full Text Full Text PDF PubMed Scopus (111) Google Scholar, A.P. Patel K. Miyamoto Y. Wygant J.N. Woodside D.G. McIntyre B.W. Immunology. 2000; 99: 62-68Crossref PubMed Scopus (27) Google Scholar). Thus, the can promote cell adhesion in to the activities of amino acid transporters. CD98hc combines with several different light chains to form a series of heterodimers that are involved in amino acid transport. CD98hc binds to integrin β1A cytoplasmic domains and blocks the capacity of β1A cytoplasmic domains to suppress integrin activation (CODS). We have compared the structural requirements of CD98hc for interaction with integrins with those involved in regulation of amino acid transport. Here we report that: 1) mutation of cysteines that disrupt CD98 heavy-light chain and amino acid transport not disrupt its binding to β1A or its effect on integrin cytoplasmic and transmembrane domains of CD98hc to another type II transmembrane protein are necessary and sufficient for binding to the integrin β1A tail and for CODS. to stimulate amino acid transport. of the cytoplasmic or transmembrane domains of CD98hc with those of the capacity of CD98hc to to β1A and regulate integrin but effects on the amino acid transport of Thus, the amino acid transport of CD98 is not required for its effects on integrin function, and amino acid transport can in the of of a covalent CD98 heterodimer is not required for its effects on integrin function. CD98hc two extracellular cysteines and is the transmembrane domain of CD98hc and in a with a cysteine in an extracellular of the light chain between transmembrane domains and R. Spindler B. Loffing J. Skelly P.J. Shoemaker C.B. Verrey F. 1998; PubMed Scopus Google Scholar). of and the covalent with the light chain but not interactions with or effects on the covalent was is that was still a Indeed, Pfeiffer R. Spindler B. Loffing J. Skelly P.J. Shoemaker C.B. Verrey F. 1998; PubMed Scopus Google Scholar) that the mutant still the surface expression of the light mutation still the transport as the a we also found that heavy chains also to the β1A Furthermore, of the light chain increased of heterodimers and amino acid transport but not integrin interactions or Consequently, that the covalent of CD98hc with a light chain is not required for its interaction with integrins or for the regulation of cytoplasmic and transmembrane domains of CD98hc are necessary and sufficient for binding to the integrin β1A tail and for effects on integrin function. of these domains was integrin interactions effects on integrins to by of these two is the of the CD98hc transmembrane domain in binding to the β1A cytoplasmic is that the CD98hc transmembrane domain the of the cytoplasmic domain to promote binding to integrin cytoplasmic integrin cytoplasmic domain protein was on that the in the have that β1A of the domain may in the membrane A. G. S. J. Biol. Chem. 1999; 274: Full Text Full Text PDF PubMed Scopus Google Scholar). Consequently, the CD98hc transmembrane domain may with a transmembrane of protein Furthermore, as and also the membrane S. Calderwood D.A. Ginsberg M.H. J. Cell 2000; PubMed Google Scholar). Thus, the localization of this in the membrane may binding of the CD98hc with proteins the transmembrane to the tail In provide the of a specific for the cytoplasmic and transmembrane domains of interaction with and regulation of β1A integrin function. of amino acid transport and integrins by CD98hc is a distinct and separable of the in the cytoplasmic or transmembrane domains of CD98hc with those of the capacity to to β1A and regulate integrin In contrast, these effect on the amino acid transport of the of the extracellular domain of CD98hc with that of in a protein that was still of integrin but not stimulate isoleucine transport. Thus, the amino acid transport activity of CD98hc is not required for its effect on integrin function. CD98hc functions as a to the light chains and to the membrane F. D.L. M.H. Pfeiffer R. J. Biol. 1999; PubMed Scopus Google Scholar, M. J. Zorzano A. 2000; PubMed Scopus Google Scholar). We found that the interaction of CD98hc with integrins and amino acid are to distinct domains of the protein and are not adhesion to the of these receptors to the cell Consequently, the interaction may to the localization of CD98 amino acid transport. CD98hc can multiple integrin-dependent including cell T-cell and cell adhesion (13Fenczik C.A. Sethi T. Ramos J.W. Hughes P.E. Ginsberg M.H. Nature. 1997; 390: 81-85Crossref PubMed Scopus (254) Google Scholar,15Ohta H. Tsurudome M. Matsumura H. Koga Y. Morikawa S. Kawano M. Kusugawa S. Komada H. Nishio M. Ito Y. EMBO J. 1994; 13: 2044-2055Crossref PubMed Scopus (75) Google Scholar, 16Chandrasekaran S. Guo N.H. Rodrigues R.G. Kaiser J. Roberts D.D. J. Biol. Chem. 1999; 274: 11408-11416Abstract Full Text Full Text PDF PubMed Scopus (111) Google Scholar, A.P. Patel K. Miyamoto Y. Wygant J.N. Woodside D.G. McIntyre B.W. Immunology. 2000; 99: 62-68Crossref PubMed Scopus (27) Google Scholar). Thus, the can promote cell adhesion in to the activities of amino acid transporters. We for their in the We Verrey and Palacin for and for
Fenczik et al. (Thu,) studied this question.