Identification and characterization of a mammalian mitochondrial ATP-binding cassette membrane protein 1 1Edited by G. von Heijne

Hogue, Douglas L.; Liu, Lin; Ling, Victor

doi:10.1006/jmbi.1998.2259

Cited by 72 publications

(62 citation statements)

References 43 publications

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“…While several studies have presented evidence of chemical and disulfide cross-linking as a surrogate for dimerization (40) we would argue that these results are evidence of physical proximity and not of a functional interaction. We would define dimerization as an interaction that results in a properly localized, functional unit.…”

Section: Discussionmentioning

confidence: 62%

Mutational Studies of G553 in TM5 of ABCG2: A Residue Potentially Involved in Dimerization

et al. 2006

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ABCG2 is an ATP-binding cassette half-transporter conferring resistance to chemotherapeutic agents such as mitoxantrone, irinotecan, and flavopiridol. With its one transmembrane and one ATP-binding domain, ABCG2 is thought to homodimerize for function. One conserved region potentially involved in dimerization is a 3-amino acid sequence in transmembrane segment 5 (residues 552-554). Mutations in the corresponding residues in the Drosophila white protein (an orthologue of ABCG2) are thought to disrupt heterodimerization. We substituted glycine 553 with leucine (G553L) followed by stable transfection in HEK 293 cells. The mutant was not detectable on the cell surface and markedly reduced protein expression levels were observed by immunoblot. A deficiency in N-linked glycosylation was suggested by reduction in molecular weight compared to the 72-kDa wild type ABCG2. Similar results were observed with the G553E mutant. Confocal microscopy demonstrated mostly ER localization of the G553L mutant in HEK 293 cells, even when coexpressed with the wild type protein. Despite its altered localization, the G553L and G553E mutants were cross-linked using amine-reactive cross-linkers with multiple arm lengths, suggesting that the monomers are in close proximity but unable to complete normal trafficking. Interestingly, when expressed in Sf9 insect cells, G553L traffics to the cell membrane but is unable to hydrolyze ATP or transport the Hoechst dye. Still, when coexpressed, the mutant interferes with the Hoechst transport activity of the wild type protein. These data show that glycine 553 is important for protein trafficking and are consistent with, but do not yet prove, its involvement in ABCG2 homodimerization.The ATP-binding cassette 1 (ABC) transporter family, with 48 known human members classified in seven subgroups, constitutes one of the largest families of membrane transporters present in all species (1). These proteins are involved in the energy-dependent transport of a † This research was supported [in part] by the Intramural Research Program of the NIH, National Cancer Institute, Center for Cancer Research.*To whom correspondence should be addressed. Tel: (301) 402-1357, Fax: (301) wide variety of substrates and play an important role in numerous genetic disorders (2), a wellcharacterized example of which is cystic fibrosis, caused by mutations of the cystic fibrosis transmembrane conductance regulator (CFTR/ABCC7) protein (3). ABC transporters are also thought be responsible for the so called multidrug resistance phenomenon in antimicrobial (4) and anticancer (5) therapy; the most extensively studied example of the latter is resistance attributed to P-glycoprotein (P-gp/ABCB1)(6). ABCG2, also called BCRP/MXR/ABCP, is a member of the G subfamily of human ABC transporters, and has been demonstrated to confer resistance to multiple cancer chemotherapeutic agents, such as mitoxantrone, flavopiridol, methotrexate, and the camptothecin derivatives SN-38 and topotecan.(7-10) In addition to a potential role in c...

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Section: Discussionmentioning

confidence: 62%

Mutational Studies of G553 in TM5 of ABCG2: A Residue Potentially Involved in Dimerization

et al. 2006

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“…Four mammalian mitochondrial transporters besides ABCB10 have been discovered: ABC7, M-ABC1, M-ABC2, and MTABC3. ABC7, M-ABC2, and M-ABC1 have been shown to possess mTPs (12,30,31). Computational analysis of MTABC3 predicts that it does not possess an mTP and therefore is likely to enter the mitochondrion via the Tom70 pathway.…”

Section: Discussionmentioning

confidence: 99%

“…Homodimerization has been observed in ABC transporters of the plasma membrane (6) and peroxisome (4), and homo-oligomerization by several monomeric subunits has recently been demonstrated in ABCG2 (42). Among mitochondrial ABC transporters, Mdl1 and M-ABC1 have been shown to oligomerize, but their partners remain unidentified (30,43). We sought to elucidate the assembly partners, if any, of ABCB10 using a chemical cross-linking methodology.…”

Section: Discussionmentioning

confidence: 99%

Targeting, Import, and Dimerization of a Mammalian Mitochondrial ATP Binding Cassette (ABC) Transporter, ABCB10 (ABC-me)

Graf

Haigh

Corson

et al. 2004

Journal of Biological Chemistry

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ATP binding cassette (ABC) transporters are a diverse superfamily of energy-dependent membrane translocases. Although responsible for the majority of transmembrane transport in bacteria, they are relatively uncommon in eukaryotic mitochondria. Organellar trafficking and import, in addition to quaternary structure assembly, of mitochondrial ABC transporters is poorly understood and may offer explanations for the paucity of their diversity. Here we examine these processes in ABCB10 (ABC-me), a mitochondrial inner membrane erythroid transporter involved in heme biosynthesis. We report that ABCB10 possesses an unusually long 105-amino acid mitochondrial targeting presequence (mTP). The central subdomain of the mTP (amino acids (aa) 36 -70) is sufficient for mitochondrial import of enhanced green fluorescent protein. The N-terminal subdomain (aa 1-35) of the mTP, although not necessary for the trafficking of ABCB10 to mitochondria, participates in the proper import of the molecule into the inner membrane. We performed a series of amino acid mutations aimed at changing specific properties of the mTP. The mTP requires neither arginine residues nor predictable ␣-helices for efficient mitochondrial targeting. Disruption of its hydrophobic character by the mutation L46Q/ I47Q, however, greatly diminishes its efficacy. This mutation can be rescued by cryptic downstream (aa 106 -715) mitochondrial targeting signals, highlighting the redundancy of this protein's targeting qualities. Mass spectrometry analysis of chemically cross-linked, immunoprecipitated ABCB10 indicates that ABCB10 embedded in the mitochondrial inner membrane homodimerizes and homo-oligomerizes. A deletion mutant of ABCB10 that lacks its mTP efficiently targets to the endoplasmic reticulum. Quaternary structure assembly of ABCB10 in the ER appears to be similar to that in the mitochondria.ABC 1 transporters comprise a large and diverse family of membrane translocases (1). Their function ranges from peptide transport to phospholipid flipping to anion channel formation. Members of the ABC transporter superfamily have been implicated in numerous human diseases (including cystic fibrosis (CFTR/ABCC7), adrenoleukodystrophy (ALDP/ABCD1), Zellweger's syndrome (PMP70/ABCD3), progressive familial intrahepatic cholestasis (SPGP/ABCB11), and Stargardt macular dystrophy (ABCR/ABCA4)) (2). The basic structure of ABC transporters is relatively well conserved and includes a hydrophilic ATP binding cassette and a hydrophobic membranespanning domain (3). Whereas the large members of the family contain two of each domain, the "half-transporters" contain one of each and are predicted to dimerize (3-6). Mammalian ABC transporters are found predominantly in the plasma membrane but are also known to play essential roles in a number of organelles, including the endoplasmic reticulum, peroxisome, and the mitochondrion (2). Mammalian mitochondrial ABC transporters have recently gained attention for their role in heme biosynthesis and iron sulfur cluster synthesis (7-12). According...

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“…24 A subgroup of ABC proteins has recently been shown to be mitochondrial. 25 The function of the rat Ian4 has recently been described by using the diabetesprone BB rat model, which is characterized by increased lymphocyte apoptosis causing lymphopenia and autoimmune diabetes. It was shown that a truncating mutation in the rIan4 gene causes lymphopenia and this …”

Section: Discussionmentioning

confidence: 99%

hIan5: the human ortholog to the rat Ian4/Iddm1/lyp is a new member of the Ian family that is overexpressed in B-cell lymphoid malignancies

et al. 2004

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The family of immune associated nucleotide binding proteins (Ian) is a distinct family of GTP-binding proteins conserved in plants, mice, rats and humans that are associated with immune functions, suggesting involvement in conserved defense mechanisms. Recently, the rat Ian4 (rIan4) was cloned and it appears to be identical to the gene Iddm1/lyp responsible for severe lymphopenia and the development of insulin-dependent diabetes in the BB-DP rat. Here we describe the characterization of a new human member of the Ian family: hIan5. hIan5 is highly homologous to rIan4, has a predicted molecular weight of 35 kDa and contains distinct G motifs of GTP-binding proteins (G-1 to G-4) in the N-terminus. Human Ian5 is anchored to the mitochondria by the hydrophobic COOH-terminal domain. Human Ian5 is highly expressed in lymph node and spleen. Different blood fractions show high hIan5 expression in CD4-and CD8-positive T cells and monocytes, but not in B lymphocytes. In contrast, in B-CLL (chronic lymphocytic leukemia) and mantle cell lymphoma samples, hIan5 mRNA was upregulated. The current data underline the role of hIan5 in T-lymphocyte development and function, and for the first time suggest that upregulation of Ian proteins is associated with B-cell malignancy, possibly by inhibiting apoptosis.

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Identification and characterization of a mammalian mitochondrial ATP-binding cassette membrane protein 1 1Edited by G. von Heijne

Cited by 72 publications

References 43 publications

Mutational Studies of G553 in TM5 of ABCG2: A Residue Potentially Involved in Dimerization

Mutational Studies of G553 in TM5 of ABCG2: A Residue Potentially Involved in Dimerization

Targeting, Import, and Dimerization of a Mammalian Mitochondrial ATP Binding Cassette (ABC) Transporter, ABCB10 (ABC-me)

hIan5: the human ortholog to the rat Ian4/Iddm1/lyp is a new member of the Ian family that is overexpressed in B-cell lymphoid malignancies

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