title: Characterization of the mitochondrial protein LETM1, which maintains the mitochondrial tubular shapes and interacts with the AAA-ATPase BCS1L.
abstract: LETM1 is located in the chromosomal region that is deleted in patients suffering Wolf-Hirschhorn syndrome; it encodes a homolog of the yeast protein Mdm38 that is involved in mitochondrial morphology. Here, we describe the LETM1-mediated regulation of the mitochondrial volume and its interaction with the mitochondrial AAA-ATPase BCS1L that is responsible for three different human disorders. LETM1 is a mitochondrial inner-membrane protein with a large domain extruding to the matrix. The LETM1 homolog LETM2 is a mitochondrial protein that is expressed preferentially in testis and sperm. LETM1 downregulation caused mitochondrial swelling and cristae disorganization, but seemed to have little effect on membrane fusion and fission. Formation of the respiratory-chain complex was impaired by LETM1 knockdown. Cells lacking mitochondrial DNA lost active respiratory chains but maintained mitochondrial tubular networks, indicating that mitochondrial swelling caused by LETM1 knockdown is not caused by the disassembly of the respiratory chains. LETM1 was co-precipitated with BCS1L and formation of the LETM1 complex depended on BCS1L levels, suggesting that BCS1L stimulates the assembly of the LETM1 complex. BCS1L knockdown caused disassembly of the respiratory chains as well as LETM1 downregulation and induced distinct changes in mitochondrial morphology.
authors.affiliation: Department of Molecular Biology, Graduate School of Medical Science, Kyushu University, Fukuoka, Japan.
authors.forename: Shoko
authors.initials: S
authors.lastname: Tamai
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Iida
authors.forename: Sadaki
authors.initials: S
authors.lastname: Yokota
authors.forename: Tomoko
authors.initials: T
authors.lastname: Sayano
authors.forename: Shoko
authors.initials: S
authors.lastname: Kiguchiya
authors.forename: Naotada
authors.initials: N
authors.lastname: Ishihara
authors.forename: Jun-Ichi
authors.initials: J
authors.lastname: Hayashi
authors.forename: Katsuyoshi
authors.initials: K
authors.lastname: Mihara
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Oka
mesh_terms: D000074183:ATPases Associated with Diverse Cellular Activities; D000251:Adenosine Triphosphatases / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D018076:DNA, Complementary / Q000378:metabolism; D015536:Down-Regulation; D014450:Electron Transport Complex III / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D006801:Humans; D008565:Membrane Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D008928:Mitochondria / Q000648:ultrastructure*; D051336:Mitochondrial Membranes / Q000378:metabolism / Q000648:ultrastructure; D024101:Mitochondrial Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*
chemical_list: C435491:BCS1L protein, human; D002135:Calcium-Binding Proteins; D018076:DNA, Complementary; C488528:LETM1 protein, human; C532823:LETM2 protein, rat; D008565:Membrane Proteins; D024101:Mitochondrial Proteins; D000251:Adenosine Triphosphatases; D000074183:ATPases Associated with Diverse Cellular Activities; D014450:Electron Transport Complex III