Sam68 impedes the recovery of arterial injury by augmenting inflammatory response.

Abstract

OBJECTIVE:

The role of Src-associated-in-mitosis-68-kDa (Sam68) in cardiovascular biology has not been studied. A recent report suggests that Sam68 promotes TNF-α-induced NF-κB activation in fibroblasts. Here we sought to dissect the molecular mechanism by which Sam68 regulates NF-κB signaling and its functional significance in vascular injury.

APPROACH AND RESULTS:

The endothelial denudation injury was induced in the carotid artery of Sam68-null (Sam68-/-) and WT mice. Sam68-/- mice displayed an accelerated re-endothelialization and attenuated neointima hyperplasia, which was associated with a reduced macrophage infiltration and lowered expression of pro-inflammatory cytokines in the injured vessels. Remarkably, the ameliorated vascular remodeling was recapitulated in WT mice after receiving transplantation of bone marrow (BM) from Sam68-/- mice, suggesting the effect was attributable to BM-derived inflammatory cells. In cultured Raw264.7 macrophages, knockdown of Sam68 resulted in a significant reduction in the TNF-α-induced expression of TNF-α, IL-1β, and IL-6 and in the level of nuclear phospho-p65, indicating attenuated NF-κB activation; and these results were confirmed in peritoneal and BM-derived macrophages of Sam68-/- vs. WT mice. Furthermore, co-immunoprecipitation and mass-spectrometry identified Filamin A (FLNA) as a novel Sam68-interacting protein upon TNF-α treatment. Loss- and gain-of-function experiments suggest that Sam68 and FLNA are mutually dependent for NF-κB activation and pro-inflammatory cytokine expression, and that the N-terminus of Sam68 is required for TRAF2-FLNA interaction.

CONCLUSIONS:

Sam68 promotes pro-inflammatory response in injured arteries and impedes recovery by interacting with FLNA to stabilize TRAF2 on the cytoskeleton and consequently potentiate NF-κB signaling.

• Authors: Shuling Han, Shiyue Xu, Junlan Zhou, Aijun Qiao, Chan Boriboun, Wenxia Ma, Huadong Li, Dauren Biyashev, Liu Yang, Eric Zhang, Qinghua Liu, Shayi Jiang, Ting C Zhao, Prasanna Krishnamurthy, Chunxiang Zhang, Stéphane Richard, Hongyu Qiu, Jianyi Zhang, Gangjian Qin
• Journal: Journal of molecular and cellular cardiology (J Mol Cell Cardiol) Vol. 137 Pg. 82-92 (12 2019) ISSN: 1095-8584 [Electronic] England
• PMID: 31639388 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2019 Elsevier Ltd. All rights reserved.

Chemical References

• Adaptor Proteins, Signal Transducing
• Cytokines
• Filamins
• Inflammation Mediators
• Khdrbs1 protein, mouse
• NF-kappa B
• RNA, Messenger
• RNA-Binding Proteins
• Tumor Necrosis Factor-alpha

Topics

• Adaptor Proteins, Signal Transducing (metabolism)
• Animals
• Carotid Arteries (pathology)
• Cytokines (genetics, metabolism)
• Endothelium, Vascular (metabolism, pathology)
• Filamins (metabolism)
• Gene Deletion
• Hyperplasia
• Inflammation (pathology)
• Inflammation Mediators (metabolism)
• Macrophages (pathology)
• Male
• Mice
• Mice, Inbred C57BL
• NF-kappa B (metabolism)
• Neointima (pathology)
• RAW 264.7 Cells
• RNA, Messenger (genetics, metabolism)
• RNA-Binding Proteins (metabolism)
• Tumor Necrosis Factor-alpha (pharmacology)