SCF/c-Kit-activated signaling and angiogenesis require Gαi1 and Gαi3

Abstract

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 (Gαi) proteins in this process. In MEFs and HUVECs, Gαi1/3 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 Gαi1/3 silencing or knockout (KO), or due to dominant negative mutations but was strengthened substantially following ectopic overexpression of Gαi1/3. SCF-induced HUVEC proliferation, migration, and capillary tube formation were suppressed after Gαi1/3 silencing or KO, or due to dominant negative mutations. In vivo , endothelial knockdown of Gαi1/3 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, Gαi1/3 mediate SCF/c-Kit-activated signaling and angiogenesis.

Targeting the mitochondrial protein YME1L to inhibit osteosarcoma cell growth in vitro and in vivo

“…A previous study demonstrated the crucial role of YME1L within glioma cells in facilitating the transcription and expression of G protein subunit alpha i1 (Gαi1) [ 27 ], a key protein essential for the activation of Akt-mTOR cascade through various receptor tyrosine kinases (RTKs) and non-RTK receptors [ 38 , 39 , 44 – 51 ]. We revealed that the suppression of YME1L, achieved through shYME1L-seq1 or shYME1L-seq2, markedly downregulated both mRNA and protein levels of Gαi1 in pOS-1 primary cells (Fig.…”

“…7H ). Crucially, in pOS-1 cells expressing shYME1L-seq1, the augmentation of Gαi1 expression via a lentiviral Gαi1-expressing construct (“oeGαi1”, from Dr. Cao [ 38 , 39 ]) reinstated the phosphorylation of Akt and S6K (Fig. 7I ).…”

“…Gαi proteins, including Gαi1 and Gαi3, were shown to associate with multiple ligand-activated RTKs, including EGFR [ 62 ], VEGFR [ 47 ], KGFR [ 50 ], TrkB [ 48 ] and c-Kit [ 39 ], essential for downstream Akt-mTOR cascade activation. Several non-RTK receptors also required Gαi1 and Gαi3 for activating the downstream Akt-mTOR cascade [ 38 , 44 , 46 , 51 ].…”

“…Following selection by puromycin stable cells were formed [ 34 ]. The lentiviral Gαi1-overexpressing construct or the empty vector, from Dr. Cao [ 38 , 39 ], was added to primary OS cells, and stable cells established after puromycin selection.…”

Pericyte-Tunnelling Nanotube-Driven Angiogenesis and C-KIT Immunolocalization in Human Developing Brain and Glioblastoma

“…The importance of SCF/c-KIT system activation in angiogenesis has been associated with the canonical mechanisms of endothelial sprouting in normal and pathological conditions [51,52]. Herein, we investigated cell distribution and immunolocalization of the c-KIT receptor to unveil its possible involvement in 'alternative' pro-angiogenic signaling pathways associated with 'unconventional' pericyte-TNT-driven vessel sprouts to promote endothelial proliferation, migration, and lumenization.…”