Liu, Youbin

Mitochondria are dynamic organelles that are able to change their morphology and cellular distribution by either fission or fusion. However, the molecular mechanisms controlling mitochondrial dynamics in vascular endothelial cells (ECs) remain largely unknown. In this study, we observed that knockdown of microtubule‐associated tumor suppressor 1 (MTUS1) in ECs inhibited tube formation and migration, accompanied with decreased promigratory signalings. We showed that MTUS1 was localized in the outer membrane of mitochondria in ECs. Knockdown of MTUS1 disturbed the elongated mitochondrial network and induced the formation of perinuclear clusters of mitochondria. Importantly, mitochondrial motility and fusion were suppressed, whereas generation of reactive oxygen species was increased in MTUS1 knockdown ECs. Mechanistically, we showed that the N‐terminal coiled‐coil domain of MTUS1 interacted with the mitochondrial membrane proteins, mitofusin‐1 and mitofusin‐2, to maintain mitochondrial morphology in ECs. This study illustrated a novel role of MTUS1 in mitochondrial morphology and EC angiogenic responses.—Wang Y., Huang Y., Liu, Y., Li, J., Hao, Y., Yin, P., Liu, Z., Chen J., Wang Y., Wang N., Zhang P., Microtubule associated tumor suppressor 1 interacts with mitofusins to regulate mitochondrial morphology in endothelial cells. FASEB J . 32, 4504–4518 (2018). www.fasebj.org

ABSTRACT Angiogenesis and inflammation are regarded as important factors in the pathogenesis of chronic inflammation, cancer, and wound healing. Recent studies have supported prior evidence that common signaling pathways are involved in angiogenesis and inflammatory responses; however, key factors controlling both processes remain unclear. Although tripartite motif‐containing (TRIM)‐28 is known to have an immunosuppressive role in immune cells, its expression level and role in endothelial cells (ECs) are still unclear. In this study, we investigated the role of TRIM28 in inflammatory responses and angiogenic activity of ECs for the first time. We showed that TRIM28 is the most abundant TRIM family member and is localized in nuclei of ECs. Small interfering RNA‐mediated knockdown of TRIM28 strikingly suppressed expression of TNF receptor (TNFR)‐1 and −2, decreased TNFα‐induced phosphorylation of IKKα/β and IκBα and degradation of IκBα and nuclear translocation of p65, and suppressed basal level and TNF‐α‐induced expression of chemokines and adhesion molecules, including VCAM‐1, IL‐6, ICAM‐1, E‐selectin, and monocyte chemoattractant protein (MCP)‐1. Unexpectedly, IL‐8 was potentiated by TRIM28 knockdown in ECs in an NF‐κB‐inducing kinase–dependent manner. Meanwhile, knockdown of TRIM28 inhibited expression of VEGF receptor 2 and suppressed VEGF‐induced proliferation and tube formation by ECs. Finally, knockdown of TRIM28 suppressed recruitment of ECs in vivo in a murine synthetic basement membrane model. In summary, we found that TRIM28 acts as a central factor in controlling endothelial inflammatory responses and angiogenic activities by retaining expression of TNFR‐1 and −2 and VEGF receptor 2 in ECs.—Wang, Y., Li, J., Huang Y., Dai, X., Liu, Y., Liu, Z., Wang, Y., Wang, N., Zhang, P. Tripartite motif–containing 28 bridges endothelial inflammation and angiogenic activity by retaining expression of TNFR1 and −2 and VEGFR2 in endothelial cells. FASEB J. 31, 2026–2036 (2017). www.fasebj.org