title: Analysis of nuclear high mobility group box 1 (HMGB1)-binding proteins in colon cancer cells: clustering with proteins involved in secretion and extranuclear function.
abstract: HMGB1 is a nuclear protein that is overexpressed and secreted in cancer cells. However, little is known about the roles of HMGB1 in the cytoplasm and secretory pathway in cancer cells. To clarify this aspect of HMGB1 function, we fractionated the cytoplasm of HCT116 colon cancer cells and used a proteomic approach to analyze cytoplasmic HMGB1-binding proteins. Pull-down experiments using recombinant HMGB1 protein as bait, followed by mass spectrometry analysis identified 162 interacting proteins. Among them were 74 proteins known to be localized exclusively to the extra-nuclear region, and 60 proteins known to be localized to both nuclear and extranuclear regions. The functions of these binding proteins include involvement in cell-cycle progression, cell proliferation, anti-apoptosis, and angiogenesis. In addition, nine of the identified proteins are related to protein translocation and secretion. These include annexin A2, myosin IC isoform a, myosin-9, and Ras-related protein Rab10, which are involved in unconventional protein secretion. Cytoplasmic HMGB1 was primarily associated with the lysosomal cytosol fraction and was colocalized with the lysosomal marker LAMP1. Our findings suggest that cytoplasmic HMGB1 binds to a number of molecules related to cancer progression and the unconventional secretory pathway.
authors.affiliation: Department of Pathology, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: Hanna
authors.initials: H
authors.lastname: Lee
authors.forename: Nara
authors.initials: N
authors.lastname: Shin
authors.forename: Meiying
authors.initials: M
authors.lastname: Song
authors.forename: Un-Beom
authors.initials: UB
authors.lastname: Kang
authors.forename: Jeonghun
authors.initials: J
authors.lastname: Yeom
authors.forename: Cheolju
authors.initials: C
authors.lastname: Lee
authors.forename: Yeong Hee
authors.initials: YH
authors.lastname: Ahn
authors.forename: Jong Shin
authors.initials: JS
authors.lastname: Yoo
authors.forename: Young-Ki
authors.initials: YK
authors.lastname: Paik
authors.forename: Hoguen
authors.initials: H
authors.lastname: Kim
mesh_terms: D015153:Blotting, Western; D002458:Cell Fractionation; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms / Q000378:metabolism*; D003593:Cytoplasm / Q000737:chemistry / Q000378:metabolism; D024243:HMGB1 Protein / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D008247:Lysosomes / Q000737:chemistry / Q000378:metabolism; D013058:Mass Spectrometry; D008856:Microscopy, Fluorescence; D009687:Nuclear Proteins / Q000737:chemistry / Q000378:metabolism; D025941:Protein Interaction Mapping / Q000379:methods*; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D055571:Secretory Pathway / Q000502:physiology
chemical_list: D024243:HMGB1 Protein; D009687:Nuclear Proteins; D011994:Recombinant Proteins