title: The role of HSP27 in RACK1-mediated PKC activation in THP-1 cells.
abstract: Receptor for Activated C Kinase 1 (RACK1) pseudosubstrate is a commercially available peptide that directly activates protein kinase C-β (PKCβ). We have recently shown that RACK1 pseudosubstrate, alone or in combination with classical immune activators, results in increased cytokine production and CD86 upregulation in primary leukocytes. Furthermore, we demonstrated a role of PKCβ and RACK1 in chemical allergen-induced CD86 expression and IL-8 production in both THP-1 cells and primary human dendritic cells. Aim of this study was to shed light on the mechanisms underlying RACK1 pseudosubstrate-induced immune activation and to compare it to lipopolysaccharide (LPS). The human promyelocytic cell line THP-1 was used throughout the study. RACK1 pseudosubstrate induced rapid (5 min) and dose-related PKCβ activation as assessed by its membrane translocation. Among the proteins phosphorylated, we identified Hsp27. Both RACK1 pseudosubstrate and LPS induce its phosphorylation and release in culture medium. The release of Hsp27 induced by RACK1 pseudosubstrate was also confirmed in peripheral blood mononuclear cells. To evaluate the role of Hsp27 in RACK1 pseudosubstrate or LPS-induced cell activation, we conducted Hsp27 silencing and neutralization experiments. Both strategies confirmed the central role of Hsp27 in RACK1 pseudosubstrate or LPS-induced cell activation, as assessed by IL-8 production and upregulation of CD86.
authors.affiliation: Laboratory of Toxicology, DiSFeB, Università degli Studi di Milano, Milan, Italy.
authors.forename: Emanuela
authors.initials: E
authors.lastname: Corsini
authors.affiliation: Laboratory of Toxicology, DiSFeB, Università degli Studi di Milano, Milan, Italy.
authors.forename: Valentina
authors.initials: V
authors.lastname: Galbiati
authors.affiliation: Laboratory of Toxicology, DiSFeB, Università degli Studi di Milano, Milan, Italy.
authors.forename: Angela
authors.initials: A
authors.lastname: Papale
authors.affiliation: Laboratory of Toxicology, DiSFeB, Università degli Studi di Milano, Milan, Italy.
authors.forename: Elena
authors.initials: E
authors.lastname: Kummer
authors.affiliation: Department of Drug Sciences - Pharmacology, University of Pavia, Viale Taramelli 14, 27100, Pavia, Italy.
authors.forename: Antonella
authors.initials: A
authors.lastname: Pinto
authors.affiliation: "Golgi Cenci" Foundation, Abbiategrasso, Italy.
authors.forename: Antonio
authors.initials: A
authors.lastname: Guaita
authors.affiliation: Department of Drug Sciences - Pharmacology, University of Pavia, Viale Taramelli 14, 27100, Pavia, Italy. racchi@unipv.it.
authors.forename: Marco
authors.initials: M
authors.lastname: Racchi
mesh_terms: D051940:B7-2 Antigen / Q000235:genetics / Q000378:metabolism; D055551:HSP27 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D006360:Heat-Shock Proteins; D006801:Humans; D016209:Interleukin-8 / Q000378:metabolism; D007963:Leukocytes, Mononuclear / Q000276:immunology*; D008070:Lipopolysaccharides / Q000276:immunology; D018832:Molecular Chaperones; D009363:Neoplasm Proteins / Q000378:metabolism*; D010766:Phosphorylation; D064546:Protein Kinase C beta / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics; D000075370:Receptors for Activated C Kinase / Q000378:metabolism*; D000074084:THP-1 Cells; D015854:Up-Regulation
chemical_list: D051940:B7-2 Antigen; D055551:HSP27 Heat-Shock Proteins; C057725:HSPB1 protein, human; D006360:Heat-Shock Proteins; D016209:Interleukin-8; D008070:Lipopolysaccharides; D018832:Molecular Chaperones; D009363:Neoplasm Proteins; C419368:RACK1 protein, human; D034741:RNA, Small Interfering; D000075370:Receptors for Activated C Kinase; D064546:Protein Kinase C beta
keywords: CD86; Cytokines; PKC; RACK1; mRNA stability