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-?-induced NF-?B activation in fibroblasts. Here we sought to dissect the molecular mechanism by which Sam68 regulates NF-?B 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-?-induced expression of TNF-?, IL-1?, and IL-6 and in the level of nuclear phospho-p65, indicating attenuated NF-?B 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-? treatment. Loss- and gain-of-function experiments suggest that Sam68 and FLNA are mutually dependent for NF-?B 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-?B signaling.

SUBMITTER: Han S 

PROVIDER: S-EPMC6889069 | biostudies-literature | 2019 Dec

REPOSITORIES: biostudies-literature