title: Regulation of proto-oncogenic dbl by chaperone-controlled, ubiquitin-mediated degradation.
abstract: The dbl proto-oncogene product is a prototype of a growing family of guanine nucleotide exchange factors (GEFs) that stimulate the activation of small GTP-binding proteins from the Rho family. Mutations that result in the loss of proto-Dbl's amino terminus produce a variant with constitutive GEF activity and high oncogenic potential. Here, we show that proto-Dbl is a short-lived protein that is kept at low levels in cells by efficient ubiquitination and degradation. The cellular fate of proto-Dbl is regulated by interactions with the chaperones Hsc70 and Hsp90 and the protein-ubiquitin ligase CHIP, and these interactions are mediated by the spectrin domain of proto-Dbl. We show that CHIP is the E3 ligase responsible for ubiquitination and proteasomal degradation of proto-Dbl, while Hsp90 functions to stabilize the protein. Onco-Dbl, lacking the spectrin homology domain, cannot bind these regulators and therefore accumulates in cells at high levels, leading to persistent stimulation of its downstream signaling pathways.
authors.affiliation: Case School of Medicine, WG-48, Case Western Reserve University, Cleveland, OH 44106, USA. danny.manor@case.edu
authors.forename: Elena
authors.initials: E
authors.lastname: Kamynina
authors.forename: Krista
authors.initials: K
authors.lastname: Kauppinen
authors.forename: Faping
authors.initials: F
authors.lastname: Duan
authors.forename: Nora
authors.initials: N
authors.lastname: Muakkassa
authors.forename: Danny
authors.initials: D
authors.lastname: Manor
mesh_terms: D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism*; D050883:HSC70 Heat-Shock Proteins / Q000378:metabolism; D018841:HSP90 Heat-Shock Proteins / Q000378:metabolism; D051379:Mice; D008954:Models, Biological; D018832:Molecular Chaperones / Q000378:metabolism*; D009154:Mutation; D041681:NIH 3T3 Cells; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D017434:Protein Structure, Tertiary; D015682:Retroviridae Proteins, Oncogenic / Q000235:genetics / Q000378:metabolism*; D013049:Spectrin / Q000737:chemistry; D018411:Spodoptera / Q000166:cytology; D014162:Transfection; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism*
chemical_list: D020662:Guanine Nucleotide Exchange Factors; D050883:HSC70 Heat-Shock Proteins; D018841:HSP90 Heat-Shock Proteins; C512843:Mcf2 protein, mouse; D018832:Molecular Chaperones; D015682:Retroviridae Proteins, Oncogenic; D013049:Spectrin; D044767:Ubiquitin-Protein Ligases; D046988:Proteasome Endopeptidase Complex