Wang X, Tao T, Song D, Mao H, Liu M, Wang J, Liu X. Calreticulin stabilizes F-actin by acetylating actin and protects microvascular endothelial cells against microwave radiation.
Life Sci 2019;
232:116591. [PMID:
31228513 DOI:
10.1016/j.lfs.2019.116591]
[Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2019] [Revised: 06/06/2019] [Accepted: 06/18/2019] [Indexed: 02/07/2023]
Abstract
AIMS
Calreticulin (CRT) is a multifunctional protein that protects endothelial cells by alleviating actin cytoskeleton injury, but the underlying mechanism remains unclear. CRT was recently identified as a novel acyltransferase; acetylation at the N-terminus of actin monomers strengthens actin polymerization. This study was undertaken to determine whether CRT protects human microvascular endothelial cells (HMECs) against microwave radiation through actin acetylation.
MATERIALS AND METHODS
We prepared a eukaryotic-derived recombinant CRT and incubated the HMECs with it prior to microwave exposure. We then assessed cell injury and endothelial function, detected actin polymerization and acetylation after HMECs exposure to S-band high-power microwaves. Coimmunoprecipitation, pull-down, and ex vitro acetylation reaction were performed to determine whether actin is a novel substrate of CRT acyltransferase. Finally, we employed the mutant experiments to demonstrate the acetylation sites contributing to CRT acetyltransferase activity.
KEY FINDINGS
Microwave radiation induced severe cell injury and endothelial contact dysfunction, reduced the polymerization of actin filaments, and destroyed the actin arrangement, ultimately reducing acetylated actin expression. CRT treatment upregulated actin acetylation levels, promoted polymerization, and facilitated thicker and longer F-actin stress fibre formation. Pre-incubation with CRT rescued microwave-induced cell injury, decreased actin acetylation, and rendered the actin cytoskeleton radiation-retardant. The level of acetyl-actin was positively correlated with actin polymerization. Actin was identified as a novel substrate of CRT, being acetylated mainly through the CRT P-domain at lys-206 and -207.
SIGNIFICANCE
This work provides a better understanding of the underlying mechanism of CRT-induced cytoprotection, and suggests a novel therapeutic target for microwave radiation-related diseases with endothelial dysfunction.
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