title: Characterization of the ubiquitin-proteasome system in bortezomib-adapted cells.
abstract: Resistance towards the proteasome inhibitor bortezomib is poorly understood. We adapted the HL-60, ARH-77 and AMO-1 cell lines (myeloid leukemia, plasmocytoid lymphoma, myeloma) to bortezomib exceeding therapeutic plasma levels, and compared characteristics of the ubiquitin-proteasome system, alternative proteases and the unfolded protein response (UPR) between adapted cells and parental lines. Adapted cells showed increased transcription rates, activities and polypeptide levels of the bortezomib-sensitive beta5, but also of the beta2 proteasome subunit and consistently retained elevated levels of active beta1/beta5-type proteasome subunits in the presence of therapeutic levels of bortezomib. Bortezomib-adapted HL-60 cells showed increased expression and proteasome association of the 11S proteasome activator, and did not accumulate poly-ubiquitinated protein, activate the UPR or UPR-mediated apoptosis in response to bortezomib. The rate of protein biosynthesis was reduced, and the transcription of chaperone genes downmodulated. We did not observe major changes in the activities of TPPII, cathepsins or deubiquitinating proteases. We conclude that different types of bortezomib-adapted cell lines, including myeloma, show similar patterns of changes in the proteasomal machinery which result in residual proteasome activity in the presence of bortezomib and a quantitative balance between protein biosynthesis and destruction.
authors.affiliation: Department of Medicine II, University of Tübingen, Tübingen, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Rückrich
authors.forename: M
authors.initials: M
authors.lastname: Kraus
authors.forename: J
authors.initials: J
authors.lastname: Gogel
authors.forename: A
authors.initials: A
authors.lastname: Beck
authors.forename: H
authors.initials: H
authors.lastname: Ovaa
authors.forename: M
authors.initials: M
authors.lastname: Verdoes
authors.forename: H S
authors.initials: HS
authors.lastname: Overkleeft
authors.forename: H
authors.initials: H
authors.lastname: Kalbacher
authors.forename: C
authors.initials: C
authors.lastname: Driessen
mesh_terms: D001897:Boronic Acids / Q000494:pharmacology*; D000069286:Bortezomib; D045744:Cell Line, Tumor; D004351:Drug Resistance; D005786:Gene Expression Regulation; D006801:Humans; D009101:Multiple Myeloma / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D014176:Protein Biosynthesis; D055550:Protein Stability; D021122:Protein Subunits; D011719:Pyrazines / Q000494:pharmacology*; D025801:Ubiquitin / Q000378:metabolism*; D015854:Up-Regulation
chemical_list: D001897:Boronic Acids; D021122:Protein Subunits; D011719:Pyrazines; D025801:Ubiquitin; D000069286:Bortezomib; D046988:Proteasome Endopeptidase Complex; C119011:26S proteasome non-ATPase regulatory subunit 13