Akt Isoforms Differentially Protect against Stroke-Induced Neuronal Injury by Regulating mTOR Activities

Abstract

Protein kinases Akt1 and Akt3 are considered to be more crucial to brain function than Akt2. We investigated the roles of Akt1 and Akt3 in stroke-induced brain injury and examined their interactions with the Akt/mTOR pathways. Focal ischemia was induced in rats. Lentiviral vectors expressing constitutively active Akt1 and Akt3 (cAkt1 and cAkt3) were injected into the ischemic cortex. Infarct sizes and gene and protein expressions in the Akt/mTOR pathways were evaluated. The results show that Akt1 and Akt3 proteins were degraded as early as 1 hour after stroke, whereas Akt2 proteins remained unchanged until 24 hours after stroke. Lentiviral-mediated overexpression of cAkt1 or cAkt3 reduced neuronal death after in vitro and in vivo ischemia. Interestingly, cAkt3 overexpression resulted in stronger protection than cAkt1 overexpression. Western blot analyses further showed that cAkt3 promoted significantly higher levels of phosphorylated Akt and phosphorylated mTOR than cAkt1. The mTOR inhibitor rapamycin blocked the protective effects of both cAkt1 and cAkt3. In conclusion, Akt isoforms are differentially regulated after stroke and Akt3 offers stronger protection than cAkt1 by maintaining Akt levels and promoting mTOR activity.

The mTOR signalling cascade: paving new roads to cure neurological disease

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p53 inhibition provides a pivotal protective effect against ischemia-reperfusion injury in vitro via mTOR signaling

“…For overexpression, the p53 cDNA was cloned from the plasmid (p53: 12136, Addgene, Cambridge, MA) into the lentiviral backbone plasmid, pHR'tripCMV-IRES-eGFP, which contains a CMV promoter and an IRES sequence between its multiple cloning site (MCS) and eGFP as previously described (Xie et al, 2013). The IRES sequence enables independent expression of both the target gene and the eGFP simultaneously.…”

Impact of microRNA-134 on neural cell survival against ischemic injury in primary cultured neuronal cells and mouse brain with ischemic stroke by targeting HSPA12B

“…All data were presented as the means7S.E. neurotransmitter function; apoptotic, autophagic, and necrotic cell death; oxidative metabolism; and protein chaperones are also altered, and are accompanied by miRNAs changing (Peng et al, 2013;Yin et al, 2010;Schratt et al, 2006;Wu and Murashov, 2013;Xie et al, 2013). This encouraged us to believe that miRNAs played an important role in neuronal cell death in the post-ischemic brain.…”