The Structure of Human 4F2hc Ectodomain Provides a Model for Homodimerization and Electrostatic Interaction with Plasma Membrane

Fort, Joana; Ballina, Laura Rodríguez de la; Burghardt, Hans; Ferrer-Costa, Carles; Turnay, Javier; Ferrer-Orta, Cristina; Usón, Isabel; Zorzano, António; Fernández‐Recio, Juan; Orozco, Modesto; Lizarbe, M.A.; Fita, Ignacio; Palacı́n, Manuel

doi:10.1074/jbc.m704524200

Cited by 107 publications

(121 citation statements)

References 51 publications

(45 reference statements)

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“…This result indicated that gB and gH interacted with CD98hc independently of each other and was in agreement with the previous report (17) on HSV-1 mutants lacking gB and/or gH. The fusion components for viral de-envelopment, which are probably induced at the nuclear membrane in HSV-1-infected cells, should include a host cell fusogenic protein(s) and perhaps cellular cofactor(s) such as CD98hc and ␤1 integrin, whose crystal structures have no structural homology with any known fusion proteins (52,53). This is suggested because (i) HSV-1 gB, the only viral fusogenic protein that has structural homology to a vesicular stomatitis virus fusion protein, glycoprotein G, plays only a minor role in viral de-envelopment fusion (17), as described above, and (ii) nuclear egress of the Drosophila cellular RNP complex may only require cellular fusion components at the nuclear membrane (3).…”

Section: Discussionsupporting

confidence: 77%

Herpes Simplex Virus 1 Recruits CD98 Heavy Chain and β1 Integrin to the Nuclear Membrane for Viral De-Envelopment

Hirohata

Arii

Liu

et al. 2015

J Virol

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Herpesviruses have evolved a unique mechanism for nucleocytoplasmic transport of nascent nucleocapsids: the nucleocapsids bud through the inner nuclear membrane (INM; primary envelopment), and the enveloped nucleocapsids then fuse with the outer nuclear membrane (de-envelopment). Little is known about the molecular mechanism of herpesviral de-envelopment. We show here that the knockdown of both CD98 heavy chain (CD98hc) and its binding partner ␤1 integrin induced membranous structures containing enveloped herpes simplex virus 1 (HSV-1) virions that are invaginations of the INM into the nucleoplasm and induced aberrant accumulation of enveloped virions in the perinuclear space and in the invagination structures. These effects were similar to those of the previously reported mutation(s) in HSV-1 proteins gB, gH, UL31, and/or Us3, which were shown here to form a complex(es) with CD98hc in HSV-1-infected cells. These results suggested that cellular proteins CD98hc and ␤1 integrin synergistically or independently regulated HSV-1 de-envelopment, probably by interacting directly and/or indirectly with these HSV-1 proteins. IMPORTANCECertain cellular and viral macromolecular complexes, such as Drosophila large ribonucleoprotein complexes and herpesvirus nucleocapsids, utilize a unique vesicle-mediated nucleocytoplasmic transport: the complexes acquire primary envelopes by budding through the inner nuclear membrane into the space between the inner and outer nuclear membranes (primary envelopment), and the enveloped complexes then fuse with the outer nuclear membrane to release de-enveloped complexes into the cytoplasm (de-envelopment). However, there is a lack of information on the molecular mechanism of de-envelopment fusion. We report here that HSV-1 recruited cellular fusion regulatory proteins CD98hc and ␤1 integrin to the nuclear membrane for viral de-envelopment fusion. This is the first report of cellular proteins required for efficient de-envelopment of macromolecular complexes during their nuclear egress. Herpesviruses are enveloped double-stranded DNA viruses that replicate their genomes and package the nascent progeny viral genomes into capsids in the nucleus, but these nascent viruses acquire their final envelopes in the cytoplasm (1, 2). Therefore, herpesvirus nucleocapsids must traverse the inner nuclear membrane (INM) and outer nuclear membrane (ONM) for viral morphogenesis. Since herpesvirus nucleocapsids are too large to cross the INM and ONM through nuclear pores, the viruses evolved a unique nuclear egress mechanism: progeny nucleocapsids acquire primary envelopes by budding through the INM into the perinuclear space between the INM and ONM (primary envelopment) and enveloped nucleocapsids then fuse with the ONM to release de-enveloped nucleocapsids into the cytoplasm (de-envelopment) (1, 2). Although this type of vesicle-mediated nucleocytoplasmic transport has not been reported previously, other than for herpesvirus nuclear egress, it has recently been reported that Drosophila cellular ribonu...

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Section: Discussionsupporting

confidence: 77%

Herpes Simplex Virus 1 Recruits CD98 Heavy Chain and β1 Integrin to the Nuclear Membrane for Viral De-Envelopment

Hirohata

Arii

Liu

et al. 2015

J Virol

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“…23 Indeed, 4F2hc serves, in addition to system y þ L, as the heavy subunit of five other amino acid transporters and has a role in b1-integrin function. 24 All the new mutations identified but two encode for severely truncated proteins, if translated, suggesting a dramatic loss of transport function in these cases. The novel large deletions (DelE6-E11 and DelE4-E11) were associated with the most severe phenotypes.…”

Section: Discussionmentioning

confidence: 99%

Novel SLC7A7 large rearrangements in lysinuric protein intolerance patients involving the same AluY repeat

et al. 2008

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Lysinuric protein intolerance (LPI) is a rare autosomal inherited disease caused by defective cationic aminoacid transport 4F2hc/y þ LAT-1 at the basolateral membrane of epithelial cells in the intestine and kidney. LPI is a multisystemic disease with a variety of clinical symptoms such as hepatosplenomegaly, osteoporosis, hypotonia, developmental delay, pulmonary insufficiency or end-stage renal disease. The SLC7A7 gene, which encodes the y þ LAT-1 protein, is mutated in LPI patients. Mutation analysis of the promoter localized in intron 1 and all exons of the SLC7A7 gene was performed in 11 patients from 9 unrelated LPI families. Point mutation screening was performed by exon direct sequencing and a new multiplex ligation probe amplification (MLPA) assay was set up for large rearrangement analysis. Eleven SLC7A7-specific mutations were identified, seven of them were novel: p.L124P, p.C425R, p.R468X, p.Y274fsX21, c.625 þ 1G4C, DelE4-E11 and DelE6-E11. The novel large deletions originated by the recombination of Alu repeats at introns 3 and 5, respectively, with the same AluY sequence localized at the SLC7A7 3 0 region. The novel MLPA assay is robust and valuable for LPI molecular diagnosis. Our results suggest that genomic rearrangements of SLC7A7 play a more important role in LPI than has been reported, increasing the detection rate from 5.1 to 21.4%. Moreover, the 3 0 region AluY repeat could be a recombination hot spot as it is involved in 38% of all SLC7A7 rearranged chromosomes described so far.

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“…According to this model, 4F2hc-ED interacts with all the extracellular loops or ends of TMDs of LAT2. 4F2hc is N-glycosylated in Pichia (18) and mammalian cells (8), and in the model the four putative sites are located in the most external face of 4F2hc-ED, out of the contact interface with LAT2 (Fig. 2B).…”

Section: Significancementioning

confidence: 99%

“…The heavy subunits are type II membrane N-glycoproteins with a single transmembrane domain (TMD), an intracellular N terminus, and a large extracellular C terminus with sequence homology with bacterial α-amylases. Indeed, the atomic structure of the extracellular domain (ED) of human 4F2hc (4F2hc-ED) is similar to that of bacterial glucosidases [i.e., a triose phosphate isomerase barrel, (βα) 8 , (subdomain A) and eight antiparallel β-strands (subdomain C)] but lacks glucosidase activity (8). The conserved cysteine residue participating in the intersubunit disulfide bridge is located between the single TMD and 4F2hc-ED.…”

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confidence: 99%

Structural bases for the interaction and stabilization of the human amino acid transporter LAT2 with its ancillary protein 4F2hc

Rosell

Meury

Álvarez-Marimon

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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119

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Heteromeric amino acid transporters (HATs) are the unique example, known in all kingdoms of life, of solute transporters composed of two subunits linked by a conserved disulfide bridge. In metazoans, the heavy subunit is responsible for the trafficking of the heterodimer to the plasma membrane, and the light subunit is the transporter. HATs are involved in human pathologies such as amino acidurias, tumor growth and invasion, viral infection and cocaine addiction. However structural information about interactions between the heavy and light subunits of HATs is scarce. In this work, transmission electron microscopy and single-particle analysis of purified human 4F2hc/L-type amino acid transporter 2 (LAT2) heterodimers overexpressed in the yeast Pichia pastoris, together with docking analysis and crosslinking experiments, reveal that the extracellular domain of 4F2hc interacts with LAT2, almost completely covering the extracellular face of the transporter. 4F2hc increases the stability of the light subunit LAT2 in detergent-solubilized Pichia membranes, allowing functional reconstitution of the heterodimer into proteoliposomes. Moreover, the extracellular domain of 4F2hc suffices to stabilize solubilized LAT2. The interaction of 4F2hc with LAT2 gives insights into the structural bases for light subunit recognition and the stabilizing role of the ancillary protein in HATs.CD98hc | 4F2hc ectodomain H eteromeric amino acid transporters (HATs) are composed of two subunits, a heavy (SLC3 family) and a light subunit [SLC7 or L-type amino acid transporter (LAT) family] linked by a conserved disulfide bridge (1). HATs are amino acid exchangers (1), and this transport activity resides in the light subunit (2). The heavy subunit (either 4F2hc or rBAT) is essential for trafficking of the holotransporter to the plasma membrane (3, 4). In mammals, six transporters heterodimerize with 4F2hc, and only one heterodimerizes with rBAT. The rBAT/b 0,+ AT complex is a dimer of heterodimers in which the light subunit is required for proper rBAT folding and stability (5, 6). In contrast, 4F2hc-associated transporters are simple heterodimers (6), and possible stabilizing roles of the two subunits in the biogenesis of the heterodimer have not been described.HATs have major impacts on human health and are involved directly in amino acidurias (cystinuria and lysinuric protein intolerance), tumor cell growth, glioma invasion, Kaposi's sarcomaassociated herpesvirus infection, and cocaine relapse (1). In addition to the role of HATs in amino acid transport, 4F2hc heterodimers mediate β1-and β3-integrin signaling (7).Structural information about HATs is scarce (1). The heavy subunits are type II membrane N-glycoproteins with a single transmembrane domain (TMD), an intracellular N terminus, and a large extracellular C terminus with sequence homology with bacterial α-amylases. Indeed, the atomic structure of the extracellular domain (ED) of human 4F2hc (4F2hc-ED) is similar to that of bacterial glucosidases [i.e., a triose phosphate isomerase barr...

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The Structure of Human 4F2hc Ectodomain Provides a Model for Homodimerization and Electrostatic Interaction with Plasma Membrane

Cited by 107 publications

References 51 publications

Herpes Simplex Virus 1 Recruits CD98 Heavy Chain and β1 Integrin to the Nuclear Membrane for Viral De-Envelopment

Herpes Simplex Virus 1 Recruits CD98 Heavy Chain and β1 Integrin to the Nuclear Membrane for Viral De-Envelopment

Novel SLC7A7 large rearrangements in lysinuric protein intolerance patients involving the same AluY repeat

Structural bases for the interaction and stabilization of the human amino acid transporter LAT2 with its ancillary protein 4F2hc

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