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Wiskott-Aldrich syndrome (WAS) is associated with mutations in the WAS protein (WASp), which plays a critical role in the initiation of T cell receptor-driven (TCR-driven) actin polymerization. The clinical phenotype of WAS includes susceptibility to infection, allergy, autoimmunity, and malignancy and overlaps with the symptoms of dedicator of cytokinesis 8 (DOCK8) deficiency, suggesting that the 2 syndromes share common pathogenic mechanisms. Here, we demonstrated that the WASp-interacting protein (WIP) bridges DOCK8 to WASp and actin in T cells. We determined that the guanine nucleotide exchange factor activity of DOCK8 is essential for the integrity of the subcortical actin cytoskeleton as well as for TCR-driven WASp activation, F-actin assembly, immune synapse formation, actin foci formation, mechanotransduction, T cell transendothelial migration, and homing to lymph nodes, all of which also depend on WASp. These results indicate that DOCK8 and WASp are in the same signaling pathway that links TCRs to the actin cytoskeleton in TCR-driven actin assembly. Further, they provide an explanation for similarities in the clinical phenotypes of WAS and DOCK8 deficiency., Introduction The integrity of the actin cytoskeleton is important for T cell migration into tissues, defense against pathogens, and immunosurveillance (1). The Wiskott-Aldrich syndrome (WAS) protein WASp plays an important [...]

Epsins are a family of ubiquitin-binding, endocytic clathrin adaptors. Mice lacking both epsins 1 and 2 (Epn1/2) die at embryonic day 10 and exhibit an abnormal vascular phenotype. To examine the angiogenic role of endothelial epsins, we generated mice with constitutive or inducible deletion of Epn1/2 in vascular endothelium. These mice exhibited no abnormal phenotypes under normal conditions, suggesting that lack of endothelial epsins 1 and 2 did not affect normal blood vessels. In tumors, however, loss of epsins 1 and 2 resulted in disorganized vasculature, significantly increased vascular permeability, and markedly retarded tumor growth. Mechanistically, we show that VEGF promoted binding of epsin to ubiquitinated VEGFR2. Loss of epsins 1 and 2 specifically impaired endocytosis and degradation of VEGFR2, which resulted in excessive VEGF signaling that compromised tumor vascular function by exacerbating nonproductive leaky angiogenesis. This suggests that tumor vasculature requires a balance in VEGF signaling to provide sufficient productive angiogenesis for tumor development and that endothelial epsins 1 and 2 negatively regulate the output of VEGF signaling. Promotion of excessive VEGF signaling within tumors via a block of epsin 1 and 2 function may represent a strategy to prevent normal angiogenesis in cancer patients who are resistant to anti-VEGF therapies., Introduction Angiogenesis, the formation of new blood vessels from preexisting vessels, is essential for embryogenesis and postnatal organ repair under physiological conditions. However, under pathological conditions, such as in cancer, [...]

Although Rho-associated kinase (ROCK) activity has been implicated in cardiovascular diseases, the tissue-and isoform-specific roles of ROCKs in the vascular response to injury are not known. To address the role of ROCKs in this process, we generated haploinsufficient Rock1 (Rock1+/-) and Rock2 (Rock2+/-) mice and performed carotid artery ligations. Following this intervention, we found reduced neointima formation in Rock1+/- mice compared with that of WT or Rock2+/- mice. This correlated with decreased vascular smooth muscle cell proliferation and survival, decreased levels proinflammatory adhesion molecule expression, and reduced leukocyte infiltration. In addition, thioglycollate-induced peritoneal leukocyte recruitment and accumulation were substantially reduced in Rock1+/- mice compared with those of WT and Rock2+/- mice. To determine the role of leukocyte-derived ROCK1 in neointima formation, we performed reciprocal bone marrow transplantation (BMT) in WT and Rock1+/- mice. Rock1+/- to WT BMT led to reduced neointima formation and leukocyte infiltration following carotid ligation compared with those of WT to WT BMT. In contrast, WT to Rock1+/- BMT resulted in increased neointima formation. These findings indicate that ROCK1 in BM-derived cells mediates neointima formation following vascular injury and suggest that ROCK1 may represent a promising therapeutic target in vascular inflammatory diseases., Introduction Vascular inflammation and smooth muscle proliferation contribute to vascular remodeling and obstructive vasculopathies such as atherosclerosis and restenosis following percutaneous coronary interventions (1), (2). The inflammatory process is characterized [...]