title: HSP binding and mitochondrial localization of p53 protein in human HT1080 and mouse C3H10T1/2 cell lines.
abstract: In normal cells, the tumor suppressor actions of p53 protein are mediated by specific DNA binding and protein-protein interactions within the nucleus. Mutant p53 proteins, however, often assume an aberrant conformation devoid of tumor suppressor activity and newly capable of binding to the cognate or inducible HSP70. Recent reports from our laboratory and others show that additional unknown proteins may also complex with mutant p53. In this study, we characterize p53:HSP complexes and their subcellular location in the transformed cell lines, human HT1080 and murine C3H10T1/2, which both contain aberrant p53 conformers. Immunoprecipitation and SDS-PAGE of p53 from whole cell lysates revealed the additional presence of a broad 70 kDa band and a 90 kDa band in both lines, while p53 isolated from nuclear lysates was free from other proteins. 2D-PAGE was used to isolate and identify HSP members from cytoplasmic and nuclear lysates by immunoprecipitation, Western blotting and protein sequencing. Anti-p53 immune complexes from cytoplasmic lysates contained not only HSC70 but also GRP75, GRP78 and a weakly basic 90 kDa protein, which may be related to HSP90. The inducible form of HSP70 was not complexed to p53 protein, even though expressed in these cells. Analysis of anti-HSP70, anti-GRP75 and anti-HSP90 immune complexes suggests that HSP members exist as performed complexes in the cytoplasm, but not the nucleus. The presence of the mitochondrial and endoplasmic reticular chaperones, GRP75 and GRP78, in p53:HSP complexes suggested that p53 might be found in these cytoplasmic organelles which was confirmed in mitochondria by biochemical and immunoelectron microscopic evidence. These studies suggest that newly identified members of p53:HSP complexes represent components of a chaperone program which affects the subcellular distribution of p53 protein in these transformed lines.
authors.affiliation: Laboratory of Molecular Carcinogenesis, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA. merrick@niehs.nih.gov
authors.forename: B A
authors.initials: BA
authors.lastname: Merrick
authors.forename: C
authors.initials: C
authors.lastname: He
authors.forename: L L
authors.initials: LL
authors.lastname: Witcher
authors.forename: R M
authors.initials: RM
authors.lastname: Patterson
authors.forename: J J
authors.initials: JJ
authors.lastname: Reid
authors.forename: P M
authors.initials: PM
authors.lastname: Pence-Pawlowski
authors.forename: J K
authors.initials: JK
authors.lastname: Selkirk
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002352:Carrier Proteins / Q000032:analysis / Q000737:chemistry / Q000378:metabolism; D002461:Cell Line, Transformed; D002467:Cell Nucleus / Q000737:chemistry / Q000648:ultrastructure; D003593:Cytoplasm / Q000737:chemistry; D000091342:Endoplasmic Reticulum Chaperone BiP; D005347:Fibroblasts; D005354:Fibrosarcoma; D050883:HSC70 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins / Q000032:analysis / Q000737:chemistry / Q000378:metabolism; D018841:HSP90 Heat-Shock Proteins / Q000378:metabolism; D006360:Heat-Shock Proteins / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D008565:Membrane Proteins / Q000032:analysis / Q000737:chemistry / Q000378:metabolism; D051379:Mice; D008928:Mitochondria / Q000737:chemistry* / Q000648:ultrastructure; D018832:Molecular Chaperones / Q000032:analysis / Q000737:chemistry / Q000378:metabolism; D008969:Molecular Sequence Data; D008970:Molecular Weight; D011485:Protein Binding; D011487:Protein Conformation; D016159:Tumor Suppressor Protein p53 / Q000032:analysis* / Q000378:metabolism*
chemical_list: D002352:Carrier Proteins; D000091342:Endoplasmic Reticulum Chaperone BiP; D050883:HSC70 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; D018841:HSP90 Heat-Shock Proteins; C000717247:HSPA5 protein, human; C494371:HSPA8 protein, human; D006360:Heat-Shock Proteins; C000717248:Hspa5 protein, mouse; C494372:Hspa8 protein, mouse; D008565:Membrane Proteins; D018832:Molecular Chaperones; D016159:Tumor Suppressor Protein p53; C018551:glucose-regulated proteins