title: The BAG-1 isoform BAG-1M regulates keratin-associated Hsp70 chaperoning of aPKC in intestinal cells during activation of inflammatory signaling.
abstract: Atypical PKC (ι/λ and ζ; hereafter referred to as aPKC) is a key player in the acquisition of epithelial polarity and participates in other signaling cascades including the control of NF-κB signaling. This kinase is post-translationally regulated through Hsp70-mediated refolding. Previous work has shown that such a chaperoning activity is specifically localized to keratin intermediate filaments. Our work was performed with the goal of identifying the molecule(s) that block Hsp70 activity on keratin filaments during inflammation. A transcriptional screen allowed us to focus on BAG-1, a multi-functional protein that assists Hsp70 in nucleotide exchange but also blocks its activity at higher concentrations. We found the BAG-1 isoform BAG-1M upregulated threefold in human Caco-2 cells following stimulation with tumor necrosis factor receptor α (TNFα) to induce a pro-inflammatory response, and up to sixfold in mouse enterocytes following treatment with dextran sodium sulfate (DSS) to induce colitis. BAG-1M, but no other isoform, was found to co-purify with intermediate filaments and block Hsp70 activity in the keratin fraction but not in the soluble fraction within the range of concentrations found in epithelial cells cultured under control and inflammation conditions. Constitutive expression of BAG-1M decreased levels of phosphorylated aPKC. By contrast, knockdown of BAG-1, blocked the TNFα-induced decrease of phosphorylated aPKC. We conclude that BAG-1M mediates Hsp70 inhibition downstream of NF-κB.
authors.affiliation: Nova Southeastern University, Department of Physiology, Fort Lauderdale, FL 33314, USA University of Miami Miller School of Medicine, Department of Cell Biology, Miami, FL 33136, USA.
authors.forename: Anastasia
authors.initials: A
authors.lastname: Mashukova
authors.affiliation: University of Miami Miller School of Medicine, Department of Cell Biology, Miami, FL 33136, USA.
authors.forename: Zhanna
authors.initials: Z
authors.lastname: Kozhekbaeva
authors.affiliation: University of Miami Miller School of Medicine, Department of Cell Biology, Miami, FL 33136, USA.
authors.forename: Radia
authors.initials: R
authors.lastname: Forteza
authors.affiliation: University of Miami Miller School of Medicine, Department of Cell Biology, Miami, FL 33136, USA.
authors.forename: Vipin
authors.initials: V
authors.lastname: Dulam
authors.affiliation: University of Miami Miller School of Medicine, Department of Cell Biology, Miami, FL 33136, USA.
authors.forename: Yolanda
authors.initials: Y
authors.lastname: Figueroa
authors.affiliation: University of Miami Miller School of Medicine, Department of Cell Biology, Miami, FL 33136, USA.
authors.forename: Robert
authors.initials: R
authors.lastname: Warren
authors.affiliation: University of Miami Miller School of Medicine, Department of Cell Biology, Miami, FL 33136, USA psalas@miami.edu.
authors.forename: Pedro J
authors.initials: PJ
authors.lastname: Salas
mesh_terms: D000818:Animals; D018938:Caco-2 Cells; D003092:Colitis / Q000201:enzymology* / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007421:Intestine, Small / Q000201:enzymology / Q000276:immunology / Q000378:metabolism*; D007633:Keratins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D011493:Protein Kinase C / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: C091732:BCL2-associated athanogene 1 protein; D004268:DNA-Binding Proteins; D018840:HSP70 Heat-Shock Proteins; D016328:NF-kappa B; D014157:Transcription Factors; D007633:Keratins; C115015:PKC-3 protein; D011493:Protein Kinase C
keywords: Epithelial polarity; Intermediate filaments; Polarized signaling