title: Co-chaperones are limiting in a depleted chaperone network.
abstract: To probe the limiting nodes in the chaperoning network which maintains cellular proteostasis, we expressed a dominant negative mutant of heat shock factor 1 (dnHSF1), the regulator of the cytoplasmic proteotoxic stress response. Microarray analysis of non-stressed dnHSF1 cells showed a two- or more fold decrease in the transcript level of 10 genes, amongst which are the (co-)chaperone genes HSP90AA1, HSPA6, DNAJB1 and HSPB1. Glucocorticoid signaling, which requires the Hsp70 and the Hsp90 folding machines, was severely impaired by dnHSF1, but fully rescued by expression of DNAJA1 or DNAJB1, and partially by ST13. Expression of DNAJB6, DNAJB8, HSPA1A, HSPB1, HSPB8, or STIP1 had no effect while HSP90AA1 even inhibited. PTGES3 (p23) inhibited only in control cells. Our results suggest that the DNAJ co-chaperones in particular become limiting in a depleted chaperoning network. Our results also suggest a difference between the transcriptomes of cells lacking HSF1 and cells expressing dnHSF1.
authors.affiliation: Department of Biomolecular Chemistry 271, Radboud University Nijmegen, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands.
authors.forename: Lonneke
authors.initials: L
authors.lastname: Heldens
authors.forename: Ron P
authors.initials: RP
authors.lastname: Dirks
authors.forename: Sanne M M
authors.initials: SM
authors.lastname: Hensen
authors.forename: Carla
authors.initials: C
authors.lastname: Onnekink
authors.forename: Siebe T
authors.initials: ST
authors.lastname: van Genesen
authors.forename: François
authors.initials: F
authors.lastname: Rustenburg
authors.forename: Nicolette H
authors.initials: NH
authors.lastname: Lubsen
mesh_terms: D000818:Animals; D002460:Cell Line; D005938:Glucocorticoids / Q000378:metabolism; D050956:HSP40 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D046228:Microarray Analysis; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D015398:Signal Transduction / Q000502:physiology*
chemical_list: C494647:DNAJB1 protein, human; D005938:Glucocorticoids; D050956:HSP40 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones