The Na/K‐ATPase α1/Src interaction regulates metabolic reserve and Western diet intolerance

Abstract

Aim: Highly prevalent diseases such as insulin resistance and heart failure are characterized by reduced metabolic flexibility and reserve. We tested whether Na/K-ATPase (NKA)-mediated regulation of Src kinase, which requires two NKA sequences specific to the α1 isoform, is a regulator of metabolic capacity that can be targeted pharmacologically. Methods: Metabolic capacity was challenged functionally by Seahorse metabolic flux analyses and glucose deprivation in LLC-PK1-derived cells expressing Src binding rat NKA α1, non-Src-binding rat NKA α2 (the most abundant NKA isoform in the skeletal muscle), and Src binding gain-of-function mutant rat NKA α2. Mice with skeletal muscle-specific ablation of NKA α1 (skα1−/−) were generated using a MyoD:Cre-Lox approach and were subjected to treadmill testing and Western diet. C57/Bl6 mice were subjected to Western diet with or without pharmacological inhibition of NKA α1/Src modulation by treatment with pNaKtide, a cell-permeable peptide designed by mapping one of the sites of NKA α1/Src interaction. Results: Metabolic studies in mutant cell lines revealed that the Src binding regions of NKA α1 are required to maintain metabolic reserve and flexibility. Skα1−/− mice had decreased exercise endurance and mitochondrial Complex I dysfunction. However, skα1−/− mice were resistant to Western diet-induced insulin resistance and glucose intolerance, a protection phenocopied by pharmacological inhibition of NKA α1-mediated Src regulation with pNaKtide. Conclusions: These results suggest that NKA α1/Src regulatory function may be targeted in metabolic diseases. Because Src regulatory capability by NKA α1 is exclusive to endotherms, it may link the aerobic scope hypothesis of endothermy evolution to metabolic dysfunction.

Phosphorylation of Na+,K+-ATPase at Tyr10 of the α1-Subunit is Suppressed by AMPK and Enhanced by Ouabain in Cultured Kidney Cells

“…On the other hand, while ouabain reduced the glucose oxidation in isolated skeletal muscle, inhibition of Src family kinases by PP2 blocked this effect (Kotova et al 2006b), which not only shows that inhibition of ion transport per se is not always sufficient to alter mitochondrial function, but also highlights the link between ouabain-induced signalling via NKA and regulation of energy metabolism. Consistent with this notion, NKAα1 and Src were recently shown to play an important role in regulating mitochondrial respiration (Kutz et al 2021).…”

The microtubule network enables Src kinase interaction with the Na,K-ATPase to generate Ca2+ flashes in smooth muscle cells

“…Moreover, intracellular Ca 2+ transients were shown to modulate a phenotype of vascular smooth muscle cells via regulation of transcription factors (Kudryavtseva et al, 2013). Although, functional significance of the ouabain-induced Ca 2+ flashes was beyond the scope of this study (Glavind-Kristensen et al, 2004;Matchkov et al, 2007;Matchkov et al, 2012;Hangaard et al, 2015;Hangaard et al, 2017;Bouzinova et al, 2018;Staehr et al, 2018;Kutz et al, 2021), we can suggest based on previous reports that this spatial and temporal Ca 2+ signaling could play an important role in vascular remodeling and contraction, intracellular signaling and smooth muscle cell metabolism. This study adds further complexity in the signaling by showing the key role of microtubule network in the Na,K-ATPase-dependent intracellular signaling mediated by Src kinase.…”

“…Accordingly, it has been suggested previously that ouabain mediates, at least in part, its pro-contractile and pro-hypertensive effects via ion transport independent signaling from the Na,K-ATPase Src activation (Yuan et al, 1993;Song et al, 2014). Some controversy regarding the involvement of α1 and α2 isoforms of the Na,K-ATPase has been reported previously (Matchkov et al, 2012;Xie et al, 2015;Bouzinova et al, 2018;Staehr et al, 2018;Yu et al, 2018;Kutz et al, 2021). Although a difference in the studied tissues can contribute to the variability, previous studies demonstrated clearly that Src kinase has highest affinity to specific protein-domain on the α1 isoform (Tian et al, 2006;Xie et al, 2015;Yu et al, 2018).…”

Mitochondria – More than just batteries for cellular function

“…A recent study by Kutz revealed the Na/K-ATPase as a modulator of the metabolic capacity and mitochondrial signaling in cardiomyocytes and as a potential target for interventions in metabolic syndrome and cardiac diseases. 5,6 Cardiac tissue has a high demand for energy and metabolic products. 7 For instance, the essential electron acceptor NAD + is often depleted in cardiac pathologies, which is probably coursed by excessive oxidative stress.…”