title: BREK/LMTK2 is a myosin VI-binding protein involved in endosomal membrane trafficking.
abstract: Myosin VI is involved in a wide range of endocytic and exocytic membrane trafficking pathways; clathrin-mediated endocytosis, intracellular transport of clathrin-coated and -uncoated vesicles, AP-1B-dependent basolateral sorting in polarized epithelial cells and secretion from the Golgi complex to the cell surface. In this study, using a yeast two-hybrid screen, we identified brain-enriched kinase/lemur tyrosine kinase 2 (BREK/LMTK2), a transmembrane serine/threonine kinase with previously unknown cellular functions, as a myosin VI-interacting protein. Several binding experiments confirmed the interaction of myosin VI with BREK in vivo and in vitro. Immunocytochemical analyses revealed that BREK localizes to cytoplasmic membrane vesicles and to perinuclear recycling endosomes. Notably, cells in which BREK was depleted by siRNA were still able to internalize transferrin molecules and to transport them to early endosomes, but were unable to transport them to perinuclear recycling endosomes. Our results show that BREK is critical for the transition of endocytosed membrane vesicles from early endosomes to recycling endosomes and also suggest an involvement of myosin VI in this pathway.
authors.affiliation: Department of Life Sciences, Graduate School of Arts and Sciences, University of Tokyo, Komaba 3-8-1, Meguro-ku, Tokyo 153-8902, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Inoue
authors.forename: Takahide
authors.initials: T
authors.lastname: Kon
authors.forename: Reiko
authors.initials: R
authors.lastname: Ohkura
authors.forename: Hisashi
authors.initials: H
authors.lastname: Yamakawa
authors.forename: Osamu
authors.initials: O
authors.lastname: Ohara
authors.forename: Jun
authors.initials: J
authors.lastname: Yokota
authors.forename: Kazuo
authors.initials: K
authors.lastname: Sutoh
mesh_terms: D000818:Animals; D002460:Cell Line; D003593:Cytoplasm / Q000737:chemistry / Q000378:metabolism; D015536:Down-Regulation; D011992:Endosomes / Q000378:metabolism*; D006801:Humans; D008565:Membrane Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D018995:Myosin Heavy Chains / Q000737:chemistry / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000378:metabolism; D014168:Transferrin / Q000378:metabolism; D022161:Transport Vesicles / Q000378:metabolism*; D020798:Two-Hybrid System Techniques
chemical_list: D008565:Membrane Proteins; D034741:RNA, Small Interfering; D014168:Transferrin; C089785:myosin VI; C470798:LMTK2 protein, human; D017346:Protein Serine-Threonine Kinases; D018995:Myosin Heavy Chains