title: Pim-1 kinase stability is regulated by heat shock proteins and the ubiquitin-proteasome pathway.
abstract: Elevated expression of the serine/threonine kinase Pim-1 increases the incidence of lymphomas in Pim-1 transgenic mice and has also been found to occur in some human cancers. Pim-1 acts as a cell survival factor and may prevent apoptosis in malignant cells. It was therefore of interest to understand to what extent maintenance and degradation of Pim-1 protein is affected by heat shock proteins (Hsp) and the ubiquitin-proteasome pathway in K562 and BV173 human leukemic cells. The half-life of Pim-1 protein in these cells was found to increase from 1.7 to 3.1 hours when induced by heat shock or by treating the cells with the proteasome inhibitor PS-341 (bortezomib). The Hsp90 inhibitor geldanamycin prevented the stabilization of Pim-1 by heat shock. Using immunoprecipitation, it was determined that Pim-1 is targeted for degradation by ubiquitin and that Hsp70 is associated with Pim-1 under these circumstances. Conversely, Hsp90 was found to protect Pim-1 from proteasomal degradation. A luminescence-based kinase assay showed that Pim-1 kinase bound to Hsp70 or Hsp90 remains active, emphasizing the importance of its overall cellular levels. This study shows how Pim-1 levels can be modulated in cells through degradation and stabilization.
authors.affiliation: School of Molecular Biosciences, Washington State University, Pullman, WA 99164-4234, USA.
authors.forename: Kate Petersen
authors.initials: KP
authors.lastname: Shay
authors.forename: Zeping
authors.initials: Z
authors.lastname: Wang
authors.forename: Pei-Xiang
authors.initials: PX
authors.lastname: Xing
authors.forename: Ian F C
authors.initials: IF
authors.lastname: McKenzie
authors.forename: Nancy S
authors.initials: NS
authors.lastname: Magnuson
mesh_terms: D000255:Adenosine Triphosphate / Q000737:chemistry; D000818:Animals; D017209:Apoptosis; D016227:Benzoquinones; D001897:Boronic Acids / Q000494:pharmacology; D000069286:Bortezomib; D045744:Cell Line, Tumor; D018274:Electroporation; D005434:Flow Cytometry; D018840:HSP70 Heat-Shock Proteins / Q000737:chemistry; D018841:HSP90 Heat-Shock Proteins / Q000737:chemistry; D006360:Heat-Shock Proteins / Q000378:metabolism*; D006358:Hot Temperature; D006801:Humans; D015151:Immunoblotting; D047468:Immunoprecipitation; D020014:K562 Cells; D047029:Lactams, Macrocyclic; D051379:Mice; D008822:Mice, Transgenic; D046988:Proteasome Endopeptidase Complex / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry / Q000502:physiology*; D011518:Proto-Oncogene Proteins / Q000737:chemistry / Q000502:physiology*; D051573:Proto-Oncogene Proteins c-pim-1; D011719:Pyrazines / Q000494:pharmacology; D011809:Quinones / Q000494:pharmacology; D013997:Time Factors; D025801:Ubiquitin / Q000737:chemistry* / Q000378:metabolism
chemical_list: D016227:Benzoquinones; D001897:Boronic Acids; D018840:HSP70 Heat-Shock Proteins; D018841:HSP90 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D047029:Lactams, Macrocyclic; D011518:Proto-Oncogene Proteins; D011719:Pyrazines; D011809:Quinones; D025801:Ubiquitin; D000069286:Bortezomib; D000255:Adenosine Triphosphate; C496634:PIM1 protein, human; C496636:Pim1 protein, mouse; D017346:Protein Serine-Threonine Kinases; D051573:Proto-Oncogene Proteins c-pim-1; D046988:Proteasome Endopeptidase Complex; C001277:geldanamycin