Protein Kinase B (PKB/AKT1) Formed Signaling Complexes with Mitochondrial Proteins and Prevented Glycolytic Energy Dysfunction in Cultured Cardiomyocytes During Ischemia-Reperfusion Injury

Abstract

Our previous studies showed that insulin stimulated AKT1 translocation into mitochondria and modulated oxidative phosphorylation complex V in cardiac muscle. This raised the possibility that mitochondrial AKT1 may regulate glycolytic oxidative phosphorylation and mitochondrial function in cardiac muscle cells. The aims of this project were to study the effects of mitochondrial AKT1 signaling on cell survival in stressed cardiomyocytes, to define the effect of mitochondrial AKT1 signaling on glycolytic bioenergetics, and to identify mitochondrial targets of AKT1 signaling in cardiomyocytes. Mitochondrial AKT1 signaling played a protective role against apoptosis and necrosis during ischemia-reperfusion stress, suppressed mitochondrial calcium overload, and alleviated mitochondrial membrane depolarization. Activation of AKT1 signaling in mitochondria increased glucose uptake, enhanced respiration efficiency, reduced superoxide generation, and increased ATP production in the cardiomyocytes. Inhibition of mitochondrial AKT attenuated insulin response, indicating that insulin regulation of ATP production required mitochondrial AKT1 signaling. A proteomic approach was used to reveal 15 novel targets of AKT1 signaling in mitochondria, including pyruvate dehydrogenase complex (PDC). We have confirmed and characterized the association of AKT1 and PDC subunits and verified a stimulatory effect of mitochondrial AKT1 on the enzymatic activity of PDC. These findings suggested that AKT1 formed protein complexes with multiple mitochondrial proteins and improved mitochondrial function in stressed cardiomyocytes. The novel AKT1 signaling targets in mitochondria may become a resource for future metabolism research.

Metabolic syndrome diminishes insulin-induced Akt activation and causes a redistribution of Akt-interacting proteins in cardiomyocytes

“…Pyruvate dehydrogenase (PDH) is another energy metabolism-related protein that is regulated by insulin. It has been reported that insulin induces Akt interaction with pyruvate dehydrogenase (PDH) complex in mitochondria, and this interaction up-regulates PDH enzymatic activity in cardiomyocytes [58]. Interestingly, Carvajal et al [55], using a similar experimental model to ours, reported a diminished level of cardiac PDH in its active form.…”

“…Mitochondria play a critical role in the regulation of myocardial metabolism and function, and it has been shown that Akt activation in mitochondria increases ATP production and minimizes oxygen consumption [58]. Furthermore, mice fed with a high fat/high sucrose diet have a diminished cardiac insulin-induced Akt and ATP synthase activation in mitochondria [62].…”

Exendin-4 protects adipose-derived mesenchymal stem cells from apoptosis induced by hydrogen peroxide through the PI3K/Akt–Sfrp2 pathways

“…Our previous studies have found that Ex-4 is an upstream activator of the PI3K/Akt signaling pathway [14], which is involved in the transduction of antiapoptotic signals in various cells under oxidative injury [32,33], and Sfrp2 has been identified as the major downstream mediator of the PI3K/Akt pathway in MSC survival under low-oxygen conditions [34,35]. We therefore speculated whether the capability of Ex-4 to recruit antiapoptotic proteins and protect ADMSCs from apoptosis was attributable to Sfrp2.…”

A small molecule activator of AKT does not reduce ischemic injury of the rat heart

“…On the other hand, hyperactivation of AKT by SC79 in the short timescale of our study (30-60 min) is unlikely to exert such profound changes on gene transcription, which might account for the lack of cardioprotection. Additionally, overexpression of myr-AKT over a 48 h period improves mitochondrial efficiency and ATP production in isolated cardiomyocytes under normoxic conditions [ 24 ], which contributed to increased tolerance to hypoxia at a later time. However, our results show that short-term activation of AKT with SC79 did not increase ATP levels at reperfusion or improve mitochondrial enzyme activity in ischemic hearts (Figure 3 ).…”