Snf1-related kinase improves cardiac mitochondrial efficiency and decreases mitochondrial uncoupling

DNA Damage and Nuclear Morphological Changes in Cardiac Hypertrophy Are Mediated by SNRK Through Actin Depolymerization

BACKGROUND

Proper nuclear organization is critical for cardiomyocyte function, because global structural remodeling of nuclear morphology and chromatin structure underpins the development and progression of cardiovascular disease. Previous reports have implicated a role for DNA damage in cardiac hypertrophy; however, the mechanism for this process is not well delineated. AMPK (AMP-activated protein kinase) family of proteins regulates metabolism and DNA damage response (DDR). Here, we examine whether a member of this family, SNRK (SNF1-related kinase), which plays a role in cardiac metabolism, is also involved in hypertrophic remodeling through changes in DDR and structural properties of the nucleus.

METHODS

We subjected cardiac-specific Snrk-/- mice to transaortic banding to assess the effect on cardiac function and DDR. In parallel, we modulated SNRK in vitro and assessed its effects on DDR and nuclear parameters. We also used phosphoproteomics to identify novel proteins that are phosphorylated by SNRK. Last, coimmunoprecipitation was used to verify Destrin (DSTN) as the binding partner of SNRK that modulates its effects on the nucleus and DDR.

RESULTS

Cardiac-specific Snrk-/- mice display worse cardiac function and cardiac hypertrophy in response to transaortic banding, and an increase in DDR marker pH2AX (phospho-histone 2AX) in their hearts. In addition, in vitro Snrk knockdown results in increased DNA damage and chromatin compaction, along with alterations in nuclear flatness and 3-dimensional volume. Phosphoproteomic studies identified a novel SNRK target, DSTN, a member of F-actin depolymerizing factor proteins that directly bind to and depolymerize F-actin. SNRK binds to DSTN, and DSTN downregulation reverses excess DNA damage and changes in nuclear parameters, in addition to cellular hypertrophy, with SNRK knockdown. We also demonstrate that SNRK knockdown promotes excessive actin depolymerization, measured by the increased ratio of G-actin to F-actin. Last, jasplakinolide, a pharmacological stabilizer of F-actin, rescues the increased DNA damage and aberrant nuclear morphology in SNRK-downregulated cells.

CONCLUSIONS

These results indicate that SNRK is a key player in cardiac hypertrophy and DNA damage through its interaction with DSTN. This interaction fine-tunes actin polymerization to reduce DDR and maintain proper cardiomyocyte nuclear shape and morphology.

Sucrose Nonfermenting-Related Kinase Expression Is Related to a Metabolic Switch in Ovarian Cancer Cells That Results in Increased Fatty Acid Oxidation

Ovarian cancer frequently metastasizes to the omentum, which is primarily comprised of adipocytes. Our previous study found that sucrose nonfermenting-related kinase (SNRK) expression is lower in advanced-stage compared with early-stage ovarian cancer tissue. In this study, SNRK knockdown was performed in ovarian cancer cell lines using lentiviral transduction and resulted in decreased cell proliferation, increased invasion, and a switch in metabolism to increased fatty acid oxidation (FAO). Our data suggest that SNRK works as a metabolic checkpoint that allows for oxidative phosphorylation and prevents FAO during a time of rapid tumor growth.

Thrombus-specific/responsive biomimetic nanomedicine for spatiotemporal thrombolysis and alleviation of myocardial ischemia/reperfusion injury

Acute myocardial infarction (AMI) is usually caused by coronary thrombosis. However, the short half-life, lack of targetability and inevitable ischemia/reperfusion injury secondary to revascularization, which characterizes tissue plasminogen activator (tPA) limit its thrombolytic efficacy for AMI. To address the targeted and site-specific delivery of tPA, the current study reports the construction of a thrombus-targeting and responsive biomimetic nanoparticle (PTPN) for spatiotemporal treatment of AMI. PTPN was constituted by the thrombus microenvironment- responsive phenylboronic acid (PBA) nanocarrier, antioxidant molecular protocatechualdehyde (PC) and tPA with thrombolytic effect, which were enclosed by the platelet membrane. The thrombus-targeting capability of the platelet membrane enabled the adhesion of PTPN to damaged endothelial cells. The nanoparticle disintegrated under slightly acid condition and re-opened the infarct-related artery during the period of ischemia. Sequentially, ROS induced by blood reperfusion was eliminated by PC released from particle disintegration, and the cardiomyocyte mitochondrial function was protected from reperfusion injury. Therefore, this thrombus-specific/responsive biomimetic nanomedicine provides a spatiotemporal paradigm for AMI treatment with promising clinical translation prospects.

Protein kinases in cardiovascular diseases

ABSTRACT

Cardiovascular disease (CVD) remains the leading cause of death worldwide. Therefore, exploring the mechanism of CVDs and critical regulatory factors is of great significance for promoting heart repair, reversing cardiac remodeling, and reducing adverse cardiovascular events. Recently, significant progress has been made in understanding the function of protein kinases and their interactions with other regulatory proteins in myocardial biology. Protein kinases are positioned as critical regulators at the intersection of multiple signals and coordinate nearly every aspect of myocardial responses, regulating contractility, metabolism, transcription, and cellular death. Equally, reconstructing the disrupted protein kinases regulatory network will help reverse pathological progress and stimulate cardiac repair. This review summarizes recent researches concerning the function of protein kinases in CVDs, discusses their promising clinical applications, and explores potential targets for future treatments.

Negative feedback of SNRK to circ-SNRK regulates cardiac function post-myocardial infarction

A limited delivery of oxygen and metabolic substrate to the heart caused by myocardial infarction (MI) impairs the cardiac function, and often results in heart failure. Here, we identified a circRNA (circ-SNRK) from SNRK (sucrose nonfermenting 1-related kinase, which can increase the cardiac mitochondrial efficiency) in cardiomyocytes (CMs). Circ-SNRK can sponge the miR-33 and in turn improved the ATP synthesis via SNRK, proving the existence of circ-SNRK - miR-33 - SNRK axis. Furthermore, we found that protein NOVA1 (NOVA alternative splicing regulator 1) could accelerate the circ-SNRK formation; a cleaved peptide (~55 kDa) from SNRK enters the nucleus and blocks the cyclization of circ-SNRK via binding to NOVA1. The aforementioned negative feedback of SNRK to circ-SNRK limited the SNRK at a proper level, and inhibited the protective role of circ-SNRK in ischemic heart. In addition, our in vivo experiment indicated that the overexpression of exogenic circ-SNRK could break this loop and improves the cardiac function post-MI in rats. Together, our results demonstrated that the negative loop of circ-SNRK with SNRK regulates the energy metabolism in CMs, thus might be a potential therapeutic target for heart failure.

Overexpression of circRNA SNRK targets miR-103-3p to reduce apoptosis and promote cardiac repair through GSK3β/β-catenin pathway in rats with myocardial infarction

Ischemic cardiomyopathy seriously endangers human health leading to a poor prognosis. Acute myocardial infarction (AMI) is the primary etiology, and the pathophysiological process concludes with the death of cardiomyocytes caused by acute and persistent ischemia and hypoxia in the coronary arteries. We identified a circRNA (circSNRK) which was downregulated in rats with myocardial infarction (MI), however, the role it plays in the MI environment is still unclear. This study contained experiments to investigate the role of circSNRK in the regulation of cardiac survival and explore the mechanisms underlying circSNRK functions. Quantitative real-time PCR (qRT-PCR) was performed to determine the circSNRK expression patterns in hearts. Gain-of-function assays were also conducted in vitro and in vivo to determine the role of circSNRK in cardiac repair. qRT-PCR, western blot, and luciferase reporter assays were used to study circRNA interactions with micro RNAs (miRNAs). Overexpression of circSNRK in cardiomyocytes reduced apoptosis and increased proliferation. Adeno associated virus 9 (AAV9) mediated myocardium overexpression of circSNRK in post MI hearts reduced cardiomyocyte apoptosis, promoted cardiomyocyte proliferation, enhanced angiogenesis, and improved cardiac functions. Overall, upregulation of circSNRK promotes cardiac survival and functional recovery after MI. Mechanistically, circSNRK regulates cardiomyocyte apoptosis and proliferation by acting as a miR-103-3p sponge and inducing increased expression of SNRK which can bind GSK3β to regulate its phosphorylated activity. And thus circSNRK may be a promising therapeutic target for improving clinical prognosis after MI.

The MicroRNA miR-696 is regulated by SNARK and reduces mitochondrial activity in mouse skeletal muscle through Pgc1α inhibition

OBJECTIVE

MicroRNAs (miRNA) are known to regulate the expression of genes involved in several physiological processes including metabolism, mitochondrial biogenesis, proliferation, differentiation, and cell death.

METHODS

Using "in silico" analyses, we identified 219 unique miRNAs that potentially bind to the 3'UTR region of a critical mitochondrial regulator, the peroxisome proliferator-activated receptor gamma coactivator (PGC) 1 alpha (Pgc1α). Of the 219 candidate miRNAs, miR-696 had one of the highest interactions at the 3'UTR of Pgc1α, suggesting that miR-696 may be involved in the regulation of Pgc1α.

RESULTS

Consistent with this hypothesis, we found that miR-696 was highly expressed in the skeletal muscle of STZ-induced diabetic mice and chronic high-fat-fed mice. C2C12 muscle cells exposed to palmitic acid also exhibited a higher expression of miR-696. This increased expression corresponded with a reduced expression of oxidative metabolism genes and reduced mitochondrial respiration. Importantly, reducing miR-696 reversed decreases in mitochondrial activity in response to palmitic acid. Using C2C12 cells treated with the AMP-activated protein kinase (AMPK) activator AICAR and skeletal muscle from AMPKα2 dominant-negative (DN) mice, we found that the signaling mechanism regulating miR-696 did not involve AMPK. In contrast, overexpression of SNF1-AMPK-related kinase (SNARK) in C2C12 cells increased miR-696 transcription while knockdown of SNARK significantly decreased miR-696. Moreover, muscle-specific transgenic mice overexpressing SNARK exhibited a lower expression of Pgc1α, elevated levels of miR-696, and reduced amounts of spontaneous activity.

CONCLUSIONS

Our findings demonstrate that metabolic stress increases miR-696 expression in skeletal muscle cells, which in turn inhibits Pgc1α, reducing mitochondrial function. SNARK plays a role in this process as a metabolic stress signaling molecule inducing the expression of miR-696.

DHA Supplementation Attenuates MI-Induced LV Matrix Remodeling and Dysfunction in Mice

Objective

Myocardial ischemia and reperfusion (I/R) injury is associated with oxidative stress and inflammation, leading to scar development and malfunction. The marine omega-3 fatty acids (ω-3 FA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) are mediating cardioprotection and improving clinical outcomes in patients with heart disease. Therefore, we tested the hypothesis that docosahexaenoic acid (DHA) supplementation prior to LAD occlusion-induced myocardial injury (MI) confers cardioprotection in mice.

Methods

C57BL/6N mice were placed on DHA or control diets (CD) beginning 7 d prior to 60 min LAD occlusion-induced MI or sham surgery. The expression of inflammatory mediators was measured via RT-qPCR. Besides FACS analysis for macrophage quantification and subtype evaluation, macrophage accumulation as well as collagen deposition was quantified in histological sections. Cardiac function was assessed using a pressure-volume catheter for up to 14 d.

Results

DHA supplementation significantly attenuated the induction of peroxisome proliferator-activated receptor-α (PPAR-α) (2.3 ± 0.4 CD vs. 1.4 ± 0.3 DHA) after LAD occlusion. Furthermore, TNF-α (4.0 ± 0.6 CD vs. 1.5 ± 0.2 DHA), IL-1β (60.7 ± 7.0 CD vs. 11.6 ± 1.9 DHA), and IL-10 (223.8 ± 62.1 CD vs. 135.5 ± 38.5 DHA) mRNA expression increase was diminished in DHA-supplemented mice after 72 h reperfusion. These changes were accompanied by a less prominent switch in α/β myosin heavy chain isoforms. Chemokine mRNA expression was stronger initiated (CCL2 6 h: 32.8 ± 11.5 CD vs. 78.8 ± 13.6 DHA) but terminated earlier (CCL2 72 h: 39.5 ± 7.8 CD vs. 8.2 ± 1.9 DHA; CCL3 72 h: 794.3 ± 270.9 CD vs. 258.2 ± 57.8 DHA) in DHA supplementation compared to CD mice after LAD occlusion. Correspondingly, DHA supplementation was associated with a stronger increase of predominantly alternatively activated Ly6C-positive macrophage phenotype, being associated with less collagen deposition and better LV function (EF 14 d: 17.6 ± 2.6 CD vs. 31.4 ± 1.5 DHA).

Conclusion

Our data indicate that DHA supplementation mediates cardioprotection from MI via modulation of the inflammatory response with timely and attenuated remodeling. DHA seems to attenuate MI-induced cardiomyocyte injury partly by transient PPAR-α downregulation, diminishing the need for antioxidant mechanisms including mitochondrial function, or α- to β-MHC isoform switch.

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

Sucrose nonfermenting 1-related kinase (SNRK) is a serine/threonine kinase and a member of the adenosine monophosphate (AMP)-activated protein kinase (AMPK) family that is involved in the metabolic regulatory mechanisms in various cell types. SNRK is an important mediator in maintaining cellular metabolic homeostasis. In this review, we discuss the role of SNRK in metabolic tissues where it is expressed, including heart and adipose tissue. We discuss its role in regulating inflammation in these tissues and the pathways associated with regulating inflammation. We also discuss SNRK's role in vascular development and the processes associated with it. Finally, we review SNRK's potential as a target in various metabolic dysfunction-associated diseases such as cardiovascular diseases, diabetes, obesity, and cancer. This comprehensive review on SNRK suggests that it has therapeutic value in the suppression of inflammation in cardiac and adipose tissue.

Cardiomyocyte-Specific Snrk Prevents Inflammation in the Heart

Background

The SNRK (sucrose‐nonfermenting–related kinase) enzyme is critical for cardiac function. However, the underlying cause for heart failure observed in Snrk cardiac conditional knockout mouse is unknown.

Methods and Results

Previously, 6‐month adult mice knocked out for Snrk in cardiomyocytes (CMs) displayed left ventricular dysfunction. Here, 4‐month adult mice, on angiotensin II (Ang II) infusion, show rapid decline in cardiac systolic function, which leads to heart failure and death in 2 weeks. These mice showed increased expression of nuclear factor κ light chain enhancer of activated B cells (NF‐κB), inflammatory signaling proteins, proinflammatory proteins in the heart, and fibrosis. Interestingly, under Ang II infusion, mice knocked out for Snrk in endothelial cells did not show significant systolic or diastolic dysfunction. Although an NF‐κB inflammation signaling pathway was increased in Snrk knockout endothelial cells, this did not lead to fibrosis or mortality. In hearts of adult mice knocked out for Snrk in CMs, we also observed NF‐κB pathway activation in CMs, and an increased presence of Mac2⁺ macrophages was observed in basal and Ang II–infused states. In vitro analysis of Snrk knockdown HL‐1 CMs revealed similar upregulation of the NF‐κB signaling proteins and proinflammatory proteins that was exacerbated on Ang II treatment. The Ang II–induced NF‐κB pathway–mediated proinflammatory effects were mediated in part through protein kinase B or AKT, wherein AKT inhibition restored the proinflammatory signaling protein levels to baseline in Snrk knockdown HL‐1 CMs.

Conclusions

During heart failure, SNRK acts as a cardiomyocyte‐specific repressor of cardiac inflammation and fibrosis.

Dysregulation of PP2A-Akt interaction contributes to Sucrose non-fermenting related kinase (SNRK) deficiency induced insulin resistance in adipose tissue

Objective

We previously identified Sucrose non-fermenting related kinase (SNRK) as a regulator of adipose inflammation and energy homeostasis. In this study, we aimed to investigate the role of SNRK in insulin signaling in white (WAT) and brown adipose tissue (BAT).

Methods

Adipose tissue specific (SNRK deficiency in both WAT and BAT) and BAT specific knockout mouse models were employed. Phosphoproteomic studies were conducted to identify the novel SNRK pathway regulating insulin signaling in adipose tissue.

Results

SNRK ablation is sufficient to inhibit insulin-stimulated AKT phosphorylation and glucose uptake in both WAT and BAT. Phosphoproteomic study using SNRK deficient versus wild type BAT samples revealed 99% reduction of phosphorylation on Serine 80 of PPP2R5D, the regulatory subunit of Protein phosphatase 2A (PP2A). Drastic (142.5-fold) induction of phosphorylation on Serine 80 of PPP2R5D was observed in SNRK-deficient primary brown adipocytes overexpressing SNRK compared to control protein. In vitro phosphorylation reaction followed by targeted phosphoproteomic detection further confirms that human recombinant SNRK is able to phosphorylate human recombinant PPP2R5D. Dephosphorylated PPP2R5D promotes constitutive assembly of PP2A-AKT complex, therefore inhibits insulin-induced AKT phosphorylation and subsequent glucose uptake in both BAT and WAT. Knockdown of PPP2R5D in adipocytes can improve insulin sensitivity in adipocytes without SNRK expression.

Conclusions

Our findings demonstrate that SNRK regulates insulin signaling through controlling PPP2R5D phosphorylation, which subsequently impacts PP2A activity and then AKT phosphorylation in both WAT and BAT. SNRK may represent a promising potential target for treating insulin resistance-related metabolic disorders.

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SNRK is essential for insulin-stimulated AKT phosphorylation in adipose tissue.

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SNRK ablation causes insulin resistance in both white and brown adipose tissue.

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Phosphoproteomic studies identify PPP2R5D as a novel substrate of SNRK.

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SNRK regulates PP2A-AKT interaction through PPP2R5D phosphorylation.

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Enhanced PP2A activity by SNRK ablation inhibits AKT phosphorylation.

Circulating miR-103a-3p contributes to angiotensin II-induced renal inflammation and fibrosis via a SNRK/NF-κB/p65 regulatory axis

Although angiotensin II (AngII) is known to cause renal injury and fibrosis, the underlying mechanisms remain poorly characterized. Here we show that hypertensive nephropathy (HN) patients and AngII-infused mice exhibit elevated levels of circulating miR103a-3p. We observe a positive correlation between miR-103a-3p levels and AngII-induced renal dysfunction. miR-103a-3p suppresses expression of the sucrose non-fermentable-related serine/threonine-protein kinase SNRK in glomerular endothelial cells, and glomeruli of HN patients and AngII-infused mice show reduced endothelial expression of SNRK. We find that SNRK exerts anti-inflammatory effects by interacting with activated nuclear factor-κB (NF-κB)/p65. Overall, we demonstrate that AngII increases circulating miR-103a-3p levels, which reduces SNRK levels in glomerular endothelial cells, resulting in the over-activation of NF-κB/p65 and, consequently, renal inflammation and fibrosis. Together, our work identifies miR-103a-3p/SNRK/NF-κB/p65 as a regulatory axis of AngII-induced renal inflammation and fibrosis.

Angiotensin II is known to cause renal inflammation and fibrosis. Here Lu et al. show that levels of circulating miR-103a-3p are elevated in hypertensive nephropathy patients and in an animal model of angiotensin II-induced renal dysfunction, and that miR-103a-3p suppresses SNRK expression leading to the activation of the pro-inflammatory NF-κB pathway in glomerular endothelial cells.

The LKB1-AMPK and mTORC1 Metabolic Signaling Networks in Schwann Cells Control Axon Integrity and Myelination: Assembling and upholding nerves by metabolic signaling in Schwann cells

The Liver kinase B1 with its downstream target AMP activated protein kinase (LKB1-AMPK), and the key nutrient sensor mammalian target of rapamycin complex 1 (mTORC1) form two signaling systems that coordinate metabolic and cellular activity with changes in the environment in order to preserve homeostasis. For example, nutritional fluctuations rapidly feed back on these signaling systems and thereby affect cell-specific functions. Recent studies have started to reveal important roles of these strategic metabolic regulators in Schwann cells for the trophic support and myelination of axons. Because aberrant intermediate metabolism along with mitochondrial dysfunction in Schwann cells is mechanistically linked to nerve abnormalities found in acquired and inherited peripheral neuropathies, manipulation of the LKB1-AMPK, and mTORC1 signaling hubs may be a worthwhile therapeutic target to mitigate nerve damage in disease. Here, recent advances in our understanding of LKB1-AMPK and mTORC1 functions in Schwann cells are covered, and future research areas for this key metabolic signaling network are proposed.

Uncoupling proteins as a therapeutic target to protect the diabetic heart

Myocardial remodeling and dysfunction caused by accelerated oxidative damage is a widely reported phenomenon within a diabetic state. Altered myocardial substrate preference appears to be the major cause of enhanced oxidative stress-mediated cell injury within a diabetic heart. During this process, exacerbated free fatty acid flux causes an abnormal increase in mitochondrial membrane potential leading to the overproduction of free radical species and subsequent cell damage. Uncoupling proteins (UCPs) are expressed within the myocardium and can protect against free radical damage by modulating mitochondrial respiration, leading to reduced production of reactive oxygen species. Moreover, transgenic animals lacking UCPs have been shown to be more susceptible to oxidative damage and display reduced cardiac function when compared to wild type animals. This suggests that tight regulation of UCPs is necessary for normal cardiac function and in the prevention of diabetes-induced oxidative damage. This review aims to enhance our understanding of the pathophysiological mechanisms relating to the role of UCPs in a diabetic heart, and further discuss known pharmacological compounds and hormones that can protect a diabetic heart through the modulation of UCPs.

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

Sucrose nonfermenting-related kinase (SNRK) is a member of the AMPK-related kinase family, and its physiological role in adipose energy homeostasis and inflammation remains unknown. We previously reported that SNRK is ubiquitously and abundantly expressed in both white adipose tissue (WAT) and brown adipose tissue (BAT), but SNRK expression diminishes in adipose tissue in obesity. In this study we report novel experimental findings from both animal models and human genetics. SNRK is essential for survival; SNRK globally deficient pups die within 24 h after birth. Heterozygous mice are characterized by inflamed WAT and less BAT. Adipocyte-specific ablation of SNRK causes inflammation in WAT, ectopic lipid deposition in liver and muscle, and impaired adaptive thermogenesis in BAT. These metabolic disorders subsequently lead to decreased energy expenditure, higher body weight, and insulin resistance. We further confirm the significant association of common variants of the SNRK gene with obesity risk in humans. Through applying a phosphoproteomic approach, we identified eukaryotic elongation factor 1δ and histone deacetylase 1/2 as potential SNRK substrates. Taking these data together, we conclude that SNRK represses WAT inflammation and is essential to maintain BAT thermogenesis, making it a novel therapeutic target for treating obesity and associated metabolic disorders.

SNRK (Sucrose Nonfermenting 1-Related Kinase) Promotes Angiogenesis In Vivo

OBJECTIVE

SNRK (sucrose nonfermenting 1-related kinase) is a novel member of the AMPK (adenosine monophosphate-activated protein kinase)-related superfamily that is activated in the process of angiogenesis. Currently, little is known about the function of SNRK in angiogenesis in the physiological and pathological conditions.

APPROACH AND RESULTS

In this study, in Snrk global heterozygous knockout mice, retina angiogenesis and neovessel formation after hindlimb ischemia were suppressed. Consistently, mice with endothelial cell (EC)-specific Snrk deletion exhibited impaired retina angiogenesis, and delayed perfusion recovery and exacerbated muscle apoptosis in ischemic hindlimbs, compared with those of littermate wide-type mice. Endothelial SNRK expression was increased in the extremity vessel samples from nonischemic human. In ECs cultured in hypoxic conditions, HIF1α (hypoxia inducible factor 1α) bound to the SNRK promoter to upregulate SNRK expression. In the nuclei of hypoxic ECs, SNRK complexed with SP1 (specificity protein 1), and together, they bound to an SP1-binding motif in the ITGB1 (β1 integrin) promoter, resulting in enhanced ITGB1 expression and promoted EC migration. Furthermore, SNRK or SP1 deficiency in ECs ameliorated hypoxia-induced ITGB1 expression and, consequently, inhibited EC migration and angiogenesis.

CONCLUSIONS

Taken together, our data have revealed that SNRK/SP1-ITGB1 signaling axis promotes angiogenesis in vivo.

Crystal structure of the kinase and UBA domains of SNRK reveals a distinct UBA binding mode in the AMPK family

Sucrose non-fermenting (Snf1)-related kinase (SNRK) is a novel member of the AMP-activated protein kinase (AMPK) family and is involved in many metabolic processes. Here we report the crystal structure of an N-terminal SNRK fragment containing kinase and adjacent ubiquitin-associated (UBA) domains. This structure shows that the UBA domain binds between the N- and C-lobes of the kinase domain. The mode of UBA binding in SNRK largely resembles that in AMPK and brain specific kinase (BRSK), however, unique interactions play vital roles in stabilizing the KD-UBA interface of SNRK. We further propose a potential role of the UBA domain in the regulation of SNRK kinase activity. This study provides new insights into the structural diversities of the AMPK kinase family.