SCF/c-Kit-activated signaling and angiogenesis require Gai1 and Gai3

The stem cell factor (SCF) binds to c-Kit in endothelial cells, thus activating downstream signaling and angiogenesis. Herein, we examined the role of G protein subunit alpha inhibitory (Gai) proteins in this process. In MEFs and HUVECs, Gai1/3 was associated with SCF-activated c-Kit, promoting c-Kit endocytosis, and binding of key adaptor proteins, subsequently transducing downstream signaling. SCF-induced Akt-mTOR and Erk activation was robustly attenuated by Gai1/3 silencing or knockout (KO), or due to dominant negative mutations but was strengthened substantially following ectopic overexpression of Gai1/3. SCF-induced HUVEC proliferation, migration, and capillary tube formation were suppressed after Gai1/3 silencing or KO, or due to dominant negative mutations. In vivo, endothelial knockdown of Gai1/3 by intravitreous injection of endothelial-specific shRNA adeno-associated virus (AAV) potently reduced SCF-induced signaling and retinal angiogenesis in mice. Moreover, mRNA and protein expressions of SCF increased significantly in the retinal tissues of streptozotocin-induced diabetic retinopathy (DR) mice. SCF silencing, through intravitreous injection of SCF shRNA AAV, inhibited pathological retinal angiogenesis and degeneration of retinal ganglion cells in DR mice. Finally, the expression of SCF and c-Kit increased in proliferative retinal tissues of human patients with proliferative DR. Taken together, Gai1/3 mediate SCF/c-Kit-activated signaling and angiogenesis.

Automated summary

This study demonstrated that Gai1/3 proteins mediate SCF/c-Kit-activated signaling and angiogenesis in endothelial cells. Knockdown or knockout of Gai1/3, as well as dominant negative mutations, attenuated SCF-induced activation of Akt-mTOR and Erk, as well as endothelial cell proliferation, migration, and capillary tube formation.