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.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Adenosine Triphosphate / chemistry
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Animals
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Apoptosis
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Benzoquinones
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Boronic Acids / pharmacology
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Bortezomib
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Cell Line, Tumor
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Electroporation
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Flow Cytometry
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HSP70 Heat-Shock Proteins / chemistry
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HSP90 Heat-Shock Proteins / chemistry
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Heat-Shock Proteins / metabolism*
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Hot Temperature
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Humans
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Immunoblotting
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Immunoprecipitation
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K562 Cells
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Lactams, Macrocyclic
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Mice
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Mice, Transgenic
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Proteasome Endopeptidase Complex / chemistry*
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Proteasome Endopeptidase Complex / metabolism
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Protein Binding
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Protein Serine-Threonine Kinases / chemistry
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Protein Serine-Threonine Kinases / physiology*
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Proto-Oncogene Proteins / chemistry
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Proto-Oncogene Proteins / physiology*
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Proto-Oncogene Proteins c-pim-1
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Pyrazines / pharmacology
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Quinones / pharmacology
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Time Factors
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Ubiquitin / chemistry*
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Ubiquitin / metabolism
Substances
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Benzoquinones
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Boronic Acids
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HSP70 Heat-Shock Proteins
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HSP90 Heat-Shock Proteins
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Heat-Shock Proteins
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Lactams, Macrocyclic
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Proto-Oncogene Proteins
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Pyrazines
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Quinones
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Ubiquitin
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Bortezomib
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Adenosine Triphosphate
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PIM1 protein, human
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Pim1 protein, mouse
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Protein Serine-Threonine Kinases
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Proto-Oncogene Proteins c-pim-1
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Proteasome Endopeptidase Complex
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geldanamycin