title: Effects of geldanamycin, a heat-shock protein 90-binding agent, on T cell function and T cell nonreceptor protein tyrosine kinases.
abstract: The benzoquinoid ansamycins geldanamycin (GA), herbimycin, and their derivatives are emerging as novel therapeutic agents that act by inhibiting the 90-kDa heat-shock protein hsp90. We report that GA inhibits the proliferation of mitogen-activated T cells. GA is actively toxic to both resting and activated T cells; activated T cells appear to be especially vulnerable. The mechanism by which GA acts is reflected by its effects on an essential hsp90-dependent protein, the T cell-specific nonreceptor tyrosine kinase lck. GA treatment depletes lck levels in cultured T cells by a kinetically slow dose-dependent process. Pulse-chase analyses indicate that GA induces the very rapid degradation of newly synthesized lck molecules. GA also induces a slower degradation of mature lck populations. These results correlate with global losses in protein tyrosine kinase activity and an inability to respond to TCR stimuli, but the activity of mature lck is not immediately compromised. Although the specific proteasome inhibitor lactacystin provides marginal protection against GA-induced lck depletion, proteasome inhibition also induces changes in lck detergent solubility independent of GA application. There is no other evidence for the involvement of the proteosome. Lysosome inhibition provides quantitatively superior protection against degradation. These results indicate that pharmacologic inhibition of hsp90 chaperone function may represent a novel immunosuppressant strategy, and elaborate on the appropriate context in which to interpret losses of lck as a reporter for the pharmacology of GA in whole organisms.
authors.affiliation: Department of Pediatrics, Steele Memorial Children's Research Center, University of Arizona, Tucson, AZ 85724, USA. pyorgin@stanford.edu
authors.forename: P D
authors.initials: PD
authors.lastname: Yorgin
authors.forename: S D
authors.initials: SD
authors.lastname: Hartson
authors.forename: A M
authors.initials: AM
authors.lastname: Fellah
authors.forename: B T
authors.initials: BT
authors.lastname: Scroggins
authors.forename: W
authors.initials: W
authors.lastname: Huang
authors.forename: E
authors.initials: E
authors.lastname: Katsanis
authors.forename: J M
authors.initials: JM
authors.lastname: Couchman
authors.forename: R L
authors.initials: RL
authors.lastname: Matts
authors.forename: L
authors.initials: L
authors.lastname: Whitesell
mesh_terms: D000818:Animals; D016227:Benzoquinones; D002478:Cells, Cultured; D003546:Cysteine Endopeptidases / Q000378:metabolism; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000378:metabolism / Q000494:pharmacology*; D018841:HSP90 Heat-Shock Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D006801:Humans; D007166:Immunosuppressive Agents / Q000494:pharmacology; D019169:Jurkat Cells; D047029:Lactams, Macrocyclic; D008213:Lymphocyte Activation / Q000187:drug effects; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D008297:Male; D051379:Mice; D008811:Mice, Inbred DBA; D008934:Mitogens / Q000276:immunology; D009097:Multienzyme Complexes / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex; D011485:Protein Binding / Q000187:drug effects / Q000276:immunology; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011809:Quinones / Q000378:metabolism / Q000494:pharmacology*; D013154:Spleen / Q000166:cytology / Q000276:immunology; D013601:T-Lymphocytes / Q000187:drug effects* / Q000201:enzymology* / Q000276:immunology; D013997:Time Factors
chemical_list: D016227:Benzoquinones; D015853:Cysteine Proteinase Inhibitors; D004791:Enzyme Inhibitors; D018841:HSP90 Heat-Shock Proteins; D007166:Immunosuppressive Agents; D047029:Lactams, Macrocyclic; D008934:Mitogens; D009097:Multienzyme Complexes; D011809:Quinones; D011505:Protein-Tyrosine Kinases; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; C001277:geldanamycin