Nogo-A is a negative regulator of CNS angiogenesis

Abstract

Nogo-A is an important axonal growth inhibitor in the adult and developing CNS. In vitro, Nogo-A has been shown to inhibit migration and cell spreading of neuronal and nonneuronal cell types. Here, we studied in vivo and in vitro effects of Nogo-A on vascular endothelial cells during angiogenesis of the early postnatal brain and retina in which Nogo-A is expressed by many types of neurons. Genetic ablation or virus-mediated knock down of Nogo-A or neutralization of Nogo-A with an antibody caused a marked increase in the blood vessel density in vivo. In culture, Nogo-A inhibited spreading, migration, and sprouting of primary brain microvascular endothelial cells (MVECs) in a dose-dependent manner and induced the retraction of MVEC lamellipodia and filopodia. Mechanistically, we show that only the Nogo-A–specific Delta 20 domain exerts inhibitory effects on MVECs, but the Nogo-66 fragment, an inhibitory domain common to Nogo-A, -B, and -C, does not. Furthermore, the action of Nogo-A Delta 20 on MVECs required the intracellular activation of the Ras homolog gene family, member A (Rho-A)-associated, coiled-coil containing protein kinase (ROCK)-Myosin II pathway. The inhibitory effects of early postnatal brain membranes or cultured neurons on MVECs were relieved significantly by anti–Nogo-A antibodies. These findings identify Nogo-A as an important negative regulator of developmental angiogenesis in the CNS. They may have important implications in CNS pathologies involving angiogenesis such as stroke, brain tumors, and retinopathies.

Alterations of p75 neurotrophin receptor and Myelin transcription factor 1 in the hippocampus of perinatal phencyclidine treated rats

“…Lingo-1 (83 kDa) 36 , NgR (51 kDa) 37 , p75 (75 kDa) 38 , TROY (46 kDa) 39 , WNK1 (250 kDa) 31 , and Myt1 (135 kDa) 31 ( Figure 1). 8 …”

Nogo-A regulates vascular network architecture in the postnatal brain

“…3,4,7 Vascular remodeling further expands and refines the complex 3D vascular network of the CNS in order to adapt to local metabolic needs and neural activity. 3,4,[8][9][10] The most important currently known molecular factors regulating the complex processes of CNS angiogenesis and vascular network generation are the ligand-receptor pairs VEGF-VEGFR, bFGF-bFGFR, Dll4-Notch, and Angiopoieitin-Tie, as well as protein members of the TGF-b superfamily, the orphan receptor GPR124, Wnt family members, and DR6/TROY death receptors. 4,5,[11][12][13] Interestingly, classical axonal guidance molecules such as Netrins, Semaphorins, Slits, and Ephrins have been shown recently to not only influence growing neurons but also growing blood vessel.…”

Tetraspanin-3 is an organizer of the multi-subunit Nogo-A signaling complex

“…The possibility of an independent mode of action is supported by the observation that cells which do not express NgR1 are still able to respond to Nogo-A-Δ20 (Fournier et al, 2001;Joset et al, 2010;Kempf et al, 2014;Oertle et al, 2003). Nogo-A-Δ20 can induce effects that are not induced by Nogo-66, such as inhibition of cell spreading, and migration of fibroblasts and primary brain microvascular endothelial cells (Walchli et al, 2013). NgR1 mediates acute growth cone collapse, but it is not required for long-term inhibition of neurite outgrowth (Chivatakarn et al, 2007); in addition, the neuronal growth cone collapse that is induced by Nogo-A-Δ20 depends on protein synthesis, whereas that induced by the Nogo-66 peptide does not (Manns et al, 2014).…”

“…In vivo, full-length Nogo-A might undergo transcytosis or proteolytic cleavage, resulting in the release of active fragments such as Nogo-A-Δ20 (Joset et al, 2010;Kempf et al, 2014;Thiede-Stan and Schwab, 2015). In the developing CNS, Nogo-A-Δ20 promotes the migration of neuronal precursors but inhibits primary brain microvascular endothelial cell migration, as well as the spreading of endothelial cells and fibroblasts (Kempf et al, 2014;Mathis et al, 2010;Oertle et al, 2003;Rolando et al, 2012;Schmandke et al, 2013;Walchli et al, 2013). Although Nogo-A-Δ20 and Nogo-66 signal through different receptors, the activation of RhoA is a common intracellular signal step downstream of both inhibitory domains (Joset et al, 2010;Kempf et al, 2014;Montani et al, 2009;Nash et al, 2009).…”