Sucrose Nonfermenting-Related Kinase Enzyme–Mediated Rho-Associated Kinase Signaling is Responsible for Cardiac Function

Abstract

Background Cardiac metabolism is critical for the functioning of the heart, and disturbance in this homeostasis is likely to influence cardiac disorders or cardiomyopathy. Our lab has previously shown that sucrose non-fermenting related kinase (SNRK) enzyme, which belongs to the AMP-activated kinase (AMPK) family, was essential for cardiac metabolism in mammals. Snrk global homozygous knockout (KO) mice die at postnatal day 0, and conditional deletion of Snrk in cardiomyocytes (Snrk cmcKO) leads to cardiac failure, and death by 8–10 months. Methods and Results We performed additional cardiac functional studies using echocardiography (ECHO), and identified further cardiac functional deficits in Snrk cmcKO mice. NMR-based metabolomics analysis identified key metabolic pathway deficits in SNRK knockdown cardiomyocytes (CMs) in vitro. Specifically, metabolites involved in lipid metabolism and oxidative phosphorylation are altered and perturbations in these pathways can result in cardiac function deficits and heart failure. A phosphopeptide-based proteomic screen identified Rho-associated kinase (ROCK) as a putative substrate for SNRK and mass spec-based fragment analysis confirmed key amino acid residues on ROCK that are phosphorylated by SNRK. Western blot analysis on heart lysates from Snrk cmcKO adult mice and SNRK knockdown CMs showed increased ROCK activity. In addition, in vivo inhibition of ROCK partially rescued the in vivo Snrk cmcKO cardiac function deficits. Conclusions Collectively, our data suggests that SNRK in CMs is responsible for maintaining cardiac metabolic homeostasis, which is mediated in part by ROCK and alteration of this homeostasis influences cardiac function in the adult heart.

Sucrose Nonfermenting-Related Kinase Regulates Both Adipose Inflammation and Energy Homeostasis in Mice and Humans

“…To date, the role of SNRK in energy homeostasis has been reported only for the heart. SNRK is essential for maintaining the function of the heart; lethality has been observed in cardiomyocyte-specific SNRK knockout mice between 8 and 10 months of age, including those with heterozygous loss of SNRK in cardiomyocytes (25,27). However, findings are inconsistent concerning the effect of SNRK on lipid metabolism in the heart (25,26).…”

“…However, findings are inconsistent concerning the effect of SNRK on lipid metabolism in the heart (25,26). Cossette and colleagues (25,27) reported decreased fatty acid oxidation when SNRK expression was reduced in cardiomyocytes, with reductions of phospho-acetyl-CoA-carboxylase, phospho-AMPK, and Rhoassociated kinase, whereas Rines et al (26) reported increased fatty acid oxidation in hearts of SNRK knockout mice and decreased fatty acid oxidation with SNRK overexpression. Despite a protective effect of SNRK against ischemia/reperfusion, SNRK functions seem complex and may involve changes in mitochondria efficiency through decreasing UCP3 expression.…”

“…SNRK expression is decreased in WAT of obese mice, whereas knocking down SNRK in cultured white adipocytes increases inflammatory responses (17). SNRK has also been shown to play a role in neuronal cell apoptosis, inhibit proliferation of colon cancer cells, and contribute to the development of angioblasts in zebra fish and of cardiac metabolism in mice (21)(22)(23)(24)(25)(26)(27).…”

SNRK: a metabolic regulator with multifaceted role in development and disease

“…Cardiac metabolism Regulates cardiac metabolism through phospho-acetyl-CoA carboxylase (ACC) and phospho-AMPK signaling pathway [15] Cardiac functioning Regulates Rho-associated kinase (ROCK) signaling pathway and mitochondrial efficiency through uncoupling protein 3 (UCP3) and mitochondrial uncoupling [13,16] Cardiac inflammation Represses inflammation by regulates NF-κB phosphorylation [14] Adipose system Adipocyte glucose metabolism Regulates insulin signaling mediated glucose uptake through PPP2R5D and Akt phosphorylation [17] Adipocyte inflammation Represses inflammation in white adipose tissue through JNK and IKKβ pathways [19] Adipose thermogenesis Represses WAT inflammation and regulate BAT thermogenesis through UCP1 and PGC1α [18] Vascular system Vasculogenesis Maintain angioblast populations and control angioblast numbers in embryonic vascular development through DUSP5 [20] Angiogenesis Promote endothelial angiogenesis by activating ITGB1 (β1 integrin)mediated endothelial cell migration [21] Renal system Kidney inflammation Represses inflammation by directly interacting with NF-κB phosphorylation [22] Colorectal system Colon cancer Inhibits colon cancer cell proliferation through upregulation of calcyclin-binding protein (CacyBP) and β-catenin degradation [12] Ovarian system Ovarian cancer Omental adipocytes transport fatty acids for rapid growth, progression, and metastasis of ovarian cancer cells [23] Neuronal system Neuron apoptosis Regulates low K + -induced apoptosis in cerebral neurons [24] Table 1. The role of SNRK in various cellular systems is shown SNRK: sucrose nonfermenting 1-related kinase; AMPK: AMP-activated protein kinase; NF-κB: nuclear factor kappa-light-chain-enhancer of activated B cells; PPP2R5D: serine/threonine-protein phosphatase 2A 56 kDa regulatory subunit delta isoform; Akt: protein kinase-B; JNK: Jun N-terminal kinase; IKKβ: IκB kinase β subunit; WAT: white adipose tissue; BAT: brown adipose tissue; PGC1α: peroxisome proliferator-activated receptor γ isoform α; DUSP5: dual-specificity phosphatase 5; ITGB1: Integrin beta-1…”

“…Unlike many AMPKs, SNRK does not require an additional stimulus for activation such as increased AMP:ATP [12] ratio within a cell. SNRK also phosphorylates several proteins including Rho-associated kinase (ROCK) [12][13][14][15][16][17][18][19] . Thus, SNRK regulation and its associated signaling partners and pathways are emerging areas of research.…”