Sam68 impedes the recovery of arterial injury by augmenting inflammatory response

Academic Article

Abstract

  • © 2019 Elsevier Ltd 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.
  • Author List

  • Han S; Xu S; Zhou J; Qiao A; Boriboun C; Ma W; Li H; Biyashev D; Yang L; Zhang E
  • Start Page

  • 82
  • End Page

  • 92
  • Volume

  • 137