Gαi1/3 mediate Netrin-1-CD146-activated signaling and angiogenesis.

Netrin-1 binds to the high-affinity receptor CD146 to activate downstream signaling and angiogenesis. Here, we examine the role and underlying mechanisms of G protein subunit alpha i1 (Gαi1) and Gαi3 in Netrin-1-induced signaling and pro-angiogenic activity. In mouse embryonic fibroblasts (MEFs) and endothelial cells, Netrin-1-induced Akt-mTOR (mammalian target of rapamycin) and Erk activation was largely inhibited by silencing or knockout of Gαi1/3, whereas signaling was augmented following Gαi1/3 overexpression. Netrin-1 induced Gαi1/3 association with CD146, required for CD146 internalization, Gab1 (Grb2 associated binding protein 1) recruitment and downstream Akt-mTOR and Erk activation. Netrin-1-induced signaling was inhibited by CD146 silencing, Gab1 knockout, or Gαi1/3 dominant negative mutants. Netrin-1-induced human umbilical vein endothelial cell (HUVEC) proliferation, migration and tube formation were inhibited by Gαi1/3 short hairpin RNA (shRNA), but were potentiated by ectopic Gαi1/3 overexpression. In vivo, intravitreous injection of Netrin-1 shRNA adeno-associated virus (AAV) significantly inhibited Akt-mTOR and Erk activation in murine retinal tissues and reduced retinal angiogenesis. Endothelial knockdown of Gαi1/3 significantly inhibited Netrin1-induced signaling and retinal angiogenesis in mice. Netrin-1 mRNA and protein expression were significantly elevated in retinal tissues of diabetic retinopathy (DR) mice. Importantly, silence of Netrin-1, by intravitreous Netrin-1 shRNA AAV injection, inhibited Akt-Erk activation, pathological retinal angiogenesis and retinal ganglion cells degeneration in DR mice. Lastly, Netrin-1 and CD146 expression is significantly increased in the proliferative retinal tissues of human proliferative diabetic retinopathy patients. Together, Netrin-1 induces CD146-Gαi1/3-Gab1 complex formation to mediate downstream Akt-mTOR and Erk activation, important for angiogenesis in vitro and in vivo.

G protein inhibitory α subunit 2 is a molecular oncotarget of human glioma.

Identification of novel therapeutic oncotargets for human glioma is extremely important. Here we tested expression, potential functions and underlying mechanisms of G protein inhibitory α subunit 2 (Gαi2) in glioma. Bioinformatics analyses revealed that Gαi2 expression is significantly elevated in human glioma, correlating with poor patients' survival, higher tumor grade and wild-type IDH status. Moreover, increased Gαi2 expression was also in local glioma tissues and different glioma cells. In primary and immortalized (A172) glioma cells, Gαi2 shRNA or knockout (KO, by Cas9-sgRNA) potently suppressed viability, proliferation, and mobility, and induced apoptosis. Ectopic Gαi2 overexpression, using a lentiviral construct, further augmented malignant behaviors in glioma cells. p65 phosphorylation, NFκB activity and expression of NFκB pathway genes were decreased in Gαi2-depleted primary glioma cells, but increased following Gαi2 overexpression. There was an increased binding between Gαi2 promoter and Sp1 (specificity protein 1) transcription factor in glioma tissues and different glioma cells. In primary glioma cells Gαi2 expression was significantly reduced following Sp1 silencing, KO or inhibition. In vivo studies revealed that Gαi2 shRNA-expressing AAV intratumoral injection hindered growth of subcutaneous glioma xenografts in nude mice. Moreover, Gαi2 KO inhibited intracranial glioma xenograft in nude mice. Gαi2 depletion, NFκB inhibition and apoptosis induction were observed in subcutaneous and intracranial glioma xenografts with Gαi2 depletion. Together, overexpressed Gαi2 is important for glioma cell growth possibly by promoting NFκB cascade activation.

Yak and Tibetan sheep trampling inhibit reproductive and photosynthetic traits of Medicago ruthenica var. inschanica.

Livestock grazing affects grassland stability, resilience, and productivity owing to trampling, foraging, and excretion. Over time, trampling influences a wide range of grassland components and can have lasting effects. Trampling helps maintain grassland health but may also cause its degradation. In a field experiment over two growing seasons, we simulated yak and sheep trampling at different intensities and investigated their effects on the reproductive and photosynthetic characteristics of Medicago ruthenica var. inschanica in a Tianzhu alpine meadow in Gansu Province, China. Our results show that simulated trampling inhibited the asexual and sexual reproduction and growth of M. ruthenica. The root surface area, root volume, root biomass, pod length, pod number per unit area, number of seeds per pod, thousand-seed weight, and seed yield were significantly reduced under simulated trampling in the upper 30 cm of soil (P < 0.05) but were not reduced in the deeper soil layers (> 30 cm). Light trampling by both yak and Tibetan sheep promoted photosynthesis, while heavy trampling by both species inhibited photosynthesis. Yak trampling inhibited photosynthesis more than Tibetan sheep trampling, and overall, the adverse effects of yak trampling on asexual and sexual reproduction and growth of M. ruthenica were greater than those of Tibetan sheep trampling. Thus, the effect of yak trampling is greater than the effect of trampling by Tibetan sheep, where the different trampling intensities of yak and Tibetan sheep can result in direct but varied influences on grasslands, potentially leading to grassland differentiation.