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.

Fractional heat shock protein 27 urine excretion as a short-term predictor in acute exacerbation of chronic obstructive pulmonary disease

“…Thus, identifying patients who are at high risk for further The heat shock response is characterized by increased expression of HSPs due to stress to ensure cell integrity and minimize the extent of apoptosis (17). HSPs can be spilled into the blood system by cell damage to mediate a response by the innate immune system but also by immune cells themselves (29,41). A variety of syndromes e.g., stable COPD (24), sepsis (42) and coronary artery disease (43) are associated with altered HSP27 concentration.…”

“…As a consequence of observations on the expression of HSP27 in COPD a possible role of this protein as a useful marker also in episodes of acute exacerbation is suggested as HSP27 is released from PBMCs (29). Previous work univariable Cox proportional hazard models patients with HSP27 urine excretion below 0.845% showed significantly worse survival at 30, 90 and 180 days after discharge.…”