Protein Kinase Type Research Articles

Expression of cGMP-dependent protein kinase type I in mature white adipocytes

The presence of cGMP-dependent protein kinase I (cGKI) in murine adipocytes has been questioned, although cGKI was implicated in the thermogenic program of fat cells (FCs) and to exert anti-hypertrophic/-inflammatory effects in white adipose tissue. Herein, cGKI was detected in adipocytes from control mice, whereas FCs from global cGKI knockouts (cGKI−/−) and cGKIα rescue (αRM) mice remained cGKI-negative. cGKI mutants exhibit decreased adipocyte size, plasma leptin levels and reduced body-weights as compared to litter-matched controls. Low abundance of adiponectin in WAT and plasma of αRM animals together with previously confirmed high IL-6 levels indicate a low-grade inflammation. However, αRMs were protected from streptozotocin-induced hyperglycemia. Our results suggest that cGMP/cGKI affects both glucose and FC homeostasis in more complex mode than previously thought.

Alterations in the Cerebellar (Phospho)Proteome of a Cyclic Guanosine Monophosphate (cGMP)-dependent Protein Kinase Knockout Mouse

The cyclic nucleotide cyclic guanosine monophosphate (cGMP) plays an important role in learning and memory, but its signaling mechanisms in the mammalian brain are not fully understood. Using mass-spectrometry-based proteomics, we evaluated how the cerebellum adapts its (phospho)proteome in a knockout mouse model of cGMP-dependent protein kinase type I (cGKI). Our data reveal that a small subset of proteins in the cerebellum (∼3% of the quantified proteins) became substantially differentially expressed in the absence of cGKI. More changes were observed at the phosphoproteome level, with hundreds of sites being differentially phosphorylated between wild-type and knockout cerebellum. Most of these phosphorylated sites do not represent known cGKI substrates. An integrative computational network analysis of the data indicated that the differentially expressed proteins and proteins harboring differentially phosphorylated sites largely belong to a tight network in the Purkinje cells of the cerebellum involving important cGMP/cAMP signaling nodes (e.g. PDE5 and PKARIIβ) and Ca2+ signaling (e.g. SERCA3). In this way, removal of cGKI could be linked to impaired cerebellar long-term depression at Purkinje cell synapses. In addition, we were able to identify a set of novel putative (phospho)proteins to be considered in this network. Overall, our data improve our understanding of cerebellar cGKI signaling and suggest novel players in cGKI-regulated synaptic plasticity.

Abstract 106: GYY4137 Attenuates Post-Ischemic Adverse Remodeling and Modulates ANP-Mediated cGMP Signal Transduction

Myocardial infarction is the most frequent proximate cause of heart failure, which remains a leading cause of death in the developed world. Hydrogen sulfide (H 2 S) is emerging as an important endogenous modulator in diverse physiological and pathophysiological events. We hypothesized that the slow-releasing water-soluble H 2 S donor GYY4137 (GYY) may exert cardioprotective effects through modulation of neurohormonal response to cardiac injury. We have found that treatment for 1 week with GYY (100mg/Kg/48hr, IP) after acute myocardial infarction in rats, provides powerful sustained preservation of left ventricular (LV) dimensions and function in vivo, compared to untreated infarcted (MI), placebo- and D-propargylglycine- (PAG, an inhibitor of endogenous H 2 S synthesis) treated animals 2 and 7 days after infarct (n=6/group/time-point). LV dimensions and function in GYY-treated animals were comparable to healthy sham-operated rats. GYY-treated hearts displayed a significantly lower percentage of LV fibrosis than MI, placebo and PAG hearts, whereas PAG treated animals had significantly bigger scar size relative to GYY, at days 2 and 7 after MI. A higher density of blood vessels was found in the scar area of GYY-treated animals compared to all other infarcted groups at days 2 (P<0.0002) and 7 (P<0.01) post-MI. Furthermore, treatment with GYY resulted in increased levels of plasma atrial natriuretic peptide (ANP) compared to all groups at days 2 and 7 after MI, while cardiac mRNA expression of ANP was also significantly increased in GYY-treated rats compared to Sham (P<0.001), and all the infarcted groups (P<0.05) at day 2 after MI. Concordantly, ANP second messenger cGMP was increased in plasma at day 7 in GYY rats compared to sham and all infarcted groups (p<0.05), paralleled by higher cGMP-dependent protein kinase type I (cGKI) protein levels than sham (P<0.01), and vasodilator-stimulated phosphoprotein phosphorylation (pVASP) at the cGKI preferred site (Ser239) compared to sham and PAG (P<0.05) at day 2 post-MI. In conclusion, our data suggest that H2S attenuates adverse remodeling and may exert post-ischemic cardioprotective (pro-angiogenic, anti-fibrotic) effects in part through modulation of ANP-mediated cGMP signal transduction.

Calpain activation and CaMKIV reduction in spinal cords from hSOD1G93A mouse model.

Amyotrophic Lateral Sclerosis (ALS), a severe neurodegenerative disease, affects the upper and lower motor neurons in the brain and spinal cord. In some studies, ALS disease progression has been associated with an increase in calcium-dependent degeneration processes. Motoneurons are specifically vulnerable to sustained membrane depolarization and excessive elevation of intracellular calcium concentration. The present study analyzed intracellular events in embryonic motoneurons and adult spinal cords of the hSOD1G93A ALS mouse model. We observed activation of calpain, a calcium-dependent cysteine protease that degrades a variety of substrates, and a reduction in calcium-calmodulin dependent protein kinase type IV (CaMKIV) levels in protein extracts from spinal cords obtained at several time-points of hSOD1G93A mice disease progression. However, in cultured embryonic motoneurons these differences between controls and hSOD1G93A mutants are not evident. Our results support the hypothesis that age-dependent changes in calcium homeostasis and resulting events, e.g., calpain activation and CaMKIV processing, are involved in ALS pathogenesis.

The regulation of synaptic vesicle recycling by cGMP-dependent protein kinase type II in cerebellar granule cells under strong and sustained stimulation.

From the early periods of neurogenesis and migration, up until synaptogenesis, both nitric oxide (NO) and its downstream messenger, cGMP, are thought to influence the development of neurons. The NO/cGMP/cGMP-dependent protein kinase (cGK) pathway regulates the clustering and recruitment of synaptic proteins and vesicles to the synapse, adjusting the exoendocytic cycle to the intensity of activity and accelerating endocytosis following large-scale exocytosis. Here, we show that blockage of the N-methyl-D-aspartate receptor impairs the cycling of synaptic vesicles in a subset of boutons on cerebellar granule cells, an effect that was reversed by increasing cGMP. Furthermore, we demonstrate that presynaptic cGK type II (cGKII) plays a major role in this process. Using the FM1-43 dye to track vesicle recycling, we found that knockdown of cGKII and/or the application of a cGK inhibitor reduced the efficiency of synaptic vesicle recycling to a similar extent. Likewise, in cerebellar granule cells transfected with vGlut1-pHluorin to follow the exoendocytotic cycle, application of a cGK inhibitor slowed vesicle endocytosis when exocytosis was accelerated through strong and sustained stimulation. Additionally, ultrastructural analysis showed that cGKII knockdown or inhibition favored the formation of endosomal-like structures after strong and sustained stimulation. We conclude that cGKII controls the homeostatic balance of vesicle exocytosis and endocytosis in synaptic boutons of rat cerebellar granule cells.

Relationship between CaMK II and levosimendan against arrhythmia induced by myocardial ischemia-reperfusion in rats in vitro

Objective To evaluate the relationship between calmodulin protein kinase Ⅱ (CaMK Ⅱ) and levosimendan against arrhythmias induced by myocardial ischemia-reperfusion (I/R) in rats in vitro.Methods Thirty male Wistar rats,weighing 250-300 g,were randomly divided into 3 groups (n =10 each) using a random number table:control group (group C),I/R group and levosimendan group (group L).Their hearts were rapidly excised and perfused in a langendorff apparatus with K-H solution saturated with 95％ O2-5％ CO2 at 36.5-37.5 ℃.At 20 min of equilibration,the hearts were perfused with K-H solution for 60 min in group C.The hearts were subjected to 30 min of ischemia followed by 30 min reperfusion with K-H solution in group I/R.The hearts were subjected to 30 min of ischemia followed by 30 min reperfusion with K-H solution containing 300 nmol/L levosimendan in group L.Left ventricle developed pressure (LVDP),left ventricle end-diastolic pressure (LVEDP),+ dP/dt-dP/dtmax and heart rate (HR) were recorded immediately before ischemia and at 15 and 30 min of reperfusion.Arrhythmia was recorded during reperfusion and scored.Specimens were obtained from the apex of heart at 30 min of reperfusion for determination of the intracellular calcium concentration ([Ca2 +] i).Myocardial specimens were obtained from the left ventricle at 30 min of reperfusion to detect CaMK Ⅱ activity.Results Compared with group C,arrhythmia score,[Ca2+]i and CaMK [Ⅱ activity were significantly increased,and LVDP,+ dP/dtmax,-dP/dtmax and HR were decreased,and LVEDP was increased at 15 and 30 min of reperfusion in group I/R.Compared with group I/R,the number of ventricular premature beat,arrhythmia score,[Ca2+] i and CaMK Ⅱ activity were significantly decreased,and LVDP,+ dP/dtmax,-dP/dtmax and HR were increased,and LVEDP was decreased at 15 and 30 min of reperfusion in group L.Conclusion Inhibition of CaMK Ⅱ activity is involved in the mechanism by which levosimendan decreases the development of arrhythmias induced by myocardial I/R in rats. Key words: Calcium-calmodulin-dependent protein kinase type 2; Pyridazines; Myocardial reperfusion injury; Arrhythmias, cardiac

Catalytic activity of cGMP-dependent protein kinase type I in intact cells is independent of N-terminal autophosphorylation.

Although cGMP-dependent protein kinase type I (cGKI) is an important mediator of cGMP signaling and upcoming drug target, its in vivo-biochemistry is not well understood. Many studies showed that purified cGKI autophosphorylates multiple sites at its N-terminus. Autophosphorylation might be involved in kinase activation, but it is unclear whether this happens also in intact cells. To study cGKI autophosphorylation in vitro and in vivo, we have generated phospho-specific antisera against major in vitro-autophosphorylation sites of the cGKI isoforms, cGKIα and cGKIβ. These antisera detected specifically and with high sensitivity phospho-cGKIα (Thr58), phospho-cGKIα (Thr84), or phospho-cGKIβ (Thr56/Ser63/Ser79). Using these antisera, we show that ATP-induced autophosphorylation of cGKI in purified preparations and cell extracts did neither require nor induce an enzyme conformation capable of substrate heterophosphorylation; it was even inhibited by pre-incubation with cGMP. Interestingly, phospho-cGKI species were not detectable in intact murine cells and tissues, both under basal conditions and after induction of cGKI catalytic activity. We conclude that N-terminal phosphorylation, although readily induced in vitro, is not required for the catalytic activity of cGKIα and cGKIβ in vivo. These results will also inform screening strategies to identify novel cGKI modulators.

THU0048 Role of Calcium/Calmodulin-Dependent Kinase Type IV in Podocyte Function in Lupus Nephritis

BackgroundKidney podocytes and their slit diaphragms contribute to prevent urinary protein loss. Previously, we have shown that T cell from patients with systemic lupus erythematosus (SLE) display increased expression of...

CGMP-dependent protein kinase type II knockout mice exhibit working memory impairments, decreased repetitive behavior, and increased anxiety-like traits

Neuronal activity regulates AMPA receptor trafficking, a process that mediates changes in synaptic strength, a key component of learning and memory. This form of plasticity may be induced by stimulation of the NMDA receptor which, among its activities, increases cyclic guanosine monophosphate (cGMP) through the nitric oxide synthase pathway. cGMP-dependent protein kinase type II (cGKII) is ultimately activated via this mechanism and AMPA receptor subunit GluA1 is phosphorylated at serine 845. This phosphorylation contributes to the delivery of GluA1 to the synapse, a step that increases synaptic strength. Previous studies have shown that cGKII-deficient mice display striking spatial learning deficits in the Morris Water Maze compared to wild-type littermates as well as lowered GluA1 phosphorylation in the postsynaptic density of the prefrontal cortex (Serulle et al., 2007; Wincott et al., 2013). In the current study, we show that cGKII knockout mice exhibit impaired working memory as determined using the prefrontal cortex-dependent Radial Arm Maze (RAM). Additionally, we report reduced repetitive behavior in the Marble Burying task (MB), and heightened anxiety-like traits in the Novelty Suppressed Feeding Test (NSFT). These data suggest that cGKII may play a role in the integration of information that conveys both anxiety-provoking stimuli as well as the spatial and environmental cues that facilitate functional memory processes and appropriate behavioral response.

Human CDC2-Like Kinase 1 (CLK1): A Novel Target for Alzheimer’s Disease

The cdc2-like kinases (CLKs) are an evolutionarily conserved group of dual specificity kinases belonging to the CMGC (cyclin-dependent kinases (CDKs), mitogen-activated protein kinases (MAP kinases), glycogen synthase kinases (GSK) and CDK-like kinases). The CLK family consists of four isoforms namely CLK1, CLK2, CLK3 and CLK4. The human CLK1 encoded protein comprises 454 amino acids and the catalytic domain of CLK1 exhibits the typical protein kinase fold. CLK1 has been shown to autophosphorylate on serine, threonine and tyrosine residues and phosphorylate exogenous substrates on serine and threonine residues. CLK1 plays an important role in the regulation of RNA splicing through phosphorylation of members of the serine and arginine-rich (SR) family of splicing factors. CLK1 is involved in the pathophysiology of Alzheimer's disease by phosphorylating the serine residue in SR proteins. Nuclear speckles of the nucleoplasm contain the stored form of SR proteins and are moderately responsible for the choice of splicing sites during pre-mRNA splicing. Hence, the inhibition of CLK1 can be used as a therapeutic strategy for Alzheimer's disease. Many natural and synthetic molecules are reported to possess CLK1 inhibitory activity. Some specific examples are Marine alkaloid Leucettamine B and KH-CB19. Leucettamine B is a potent inhibitor of CLK1 (15 nM), Dyrk1A (40 nM), and Dyrk2 (35 nM) and a moderate inhibitor of CLK3 (4.5 µM) whereas KH-CB19 is a highly specific and potent inhibitor of the CLK1/CLK4. X-ray crystallographic studies have revealed the binding mode of marine sponge metabolite hymenialdisine and a dichloroindolyl enamino nitrile (KH-CB19) to CLK1. This review focuses on the role of CLKs in the pathophysiology of Alzheimer's disease and therapeutic potential of targeting CLK1 in Alzheimer's disease drug discovery and development. In addition, the recent developments in drug discovery efforts targeting human CLK1 are also highlighted.

Phosphoproteomic analysis of the non-seed vascular plant model Selaginella moellendorffii

BackgroundSelaginella (Selaginella moellendorffii) is a lycophyte which diverged from other vascular plants approximately 410 million years ago. As the first reported non-seed vascular plant genome, Selaginella genome data allow comparative analysis of genetic changes that may be associated with land plant evolution. Proteomics investigations on this lycophyte model have not been extensively reported. Phosphorylation represents the most common post-translational modifications and it is a ubiquitous regulatory mechanism controlling the functional expression of proteins inside living organisms.ResultsIn this study, polyethylene glycol fractionation and immobilized metal ion affinity chromatography were employed to isolate phosphopeptides from wild-growing Selaginella. Using liquid chromatography-tandem mass spectrometry analysis, 1593 unique phosphopeptides spanning 1104 non-redundant phosphosites with confirmed localization on 716 phosphoproteins were identified. Analysis of the Selaginella dataset revealed features that are consistent with other plant phosphoproteomes, such as the relative proportions of phosphorylated Ser, Thr, and Tyr residues, the highest occurrence of phosphosites in the C-terminal regions of proteins, and the localization of phosphorylation events outside protein domains. In addition, a total of 97 highly conserved phosphosites in evolutionary conserved proteins were identified, indicating the conservation of phosphorylation-dependent regulatory mechanisms in phylogenetically distinct plant species. On the other hand, close examination of proteins involved in photosynthesis revealed phosphorylation events which may be unique to Selaginella evolution. Furthermore, phosphorylation motif analyses identified Pro-directed, acidic, and basic signatures which are recognized by typical protein kinases in plants. A group of Selaginella-specific phosphoproteins were found to be enriched in the Pro-directed motif class.ConclusionsOur work provides the first large-scale atlas of phosphoproteins in Selaginella which occupies a unique position in the evolution of terrestrial plants. Future research into the functional roles of Selaginella-specific phosphorylation events in photosynthesis and other processes may offer insight into the molecular mechanisms leading to the distinct evolution of lycophytes.

Neuroprotective effect of muscone on glutamate-induced apoptosis in PC12 cells via antioxidant and Ca2+ antagonism

In the pathogenesis of cerebral ischemia, glutamate excitotoxicity activates N-methyl-d-aspartate (NMDA) receptors which induce calcium influx and oxidative stress. Muscone exerts potent neuroprotective activities on cerebral ischemia. However, its underlying mechanism is yet to be elucidated. In this study, we demonstrated that pretreatment with muscone in PC12 cells markedly ameliorated the loss of cell viability, mitochondrial membrane potential (MMP) collapse, the release of lactate dehydrogenase (LDH), Ca2+ overload, reactive oxygen species (ROS) generation, and cell apoptosis induced by glutamate. Furthermore, muscone also decreased NR1 (NMDA receptor subunit 1) protein expression, the ratio of Bax/Bcl-2 protein expression and prevented activitation of Ca2+/calmodulin-dependent protein kinase type II (CaMKII) and ASK1/JNK/p38 signaling pathways elicited by glutamate in PC12 cells. In conclusion, our results provided novel evidence that muscone protected PC12 cells against glutamate-induced apoptosis by attenuating ROS generation and Ca2+ influx, via NR1 and CaMKII-depended ASK-1/JNK/p38 signaling pathways.

Cholera toxin, a typical protein kinase A activator, induces G1 phase growth arrest in human bladder transitional cell carcinoma cells via inhibiting the c-Raf/MEK/ERK signaling pathway

The biotoxin cholera toxin has been demonstrated to have anti-tumor activity in numerous types of cancer, including glioma. However, the role of cholera toxin in the tumorigenesis of transitional cell carcinoma (TCC), the most common malignant tumor of the bladder, remains to be elucidated. To address this, in the present study, two TCC cell lines, T24 and UM-UC-3, were treated with cholera toxin [protein kinase A (PKA) activator] and KT5720 (PKA inhibitor). Cell survival and proliferation, cell cycle alterations and apoptosis were analyzed using Hoechst staining, the MTT assay, fluorescence microscopy and flow cytometry. Western blot analysis was used to detect the expression of proteins involved in cell cycle regulation. The results revealed that cholera toxin significantly induced G1 arrest and downregulated the expression of cyclin D1 and cyclin-dependent kinase 4/6 in the TCC cell lines, and this was rescued by KT5720. Furthermore, it was demonstrated that cholera toxin downregulated the activation of the c-Raf/Mek/Erk cascade, an important mediator of tumor cell proliferation, via the PKA-dependent c-Raf phosphorylation at Ser-43. Furthermore, inhibition of Mek activity with UO126 mimicked the effects of cholera toxin. In conclusion, these results confirmed that cholera toxin specifically inhibited proliferation and induced G1 phase arrest in human bladder TCC cells. This effect was due to PKA-dependent inactivation of the c-Raf/Mek/Erk pathway. This suggested that cholera toxin may be a viable therapeutic treatment against tumorigenesis and proliferation in bladder cancer.

Possible inhibitor from traditional Chinese medicine for the β form of calcium-dependent protein kinase type II in the treatment of major depressive disorder.

Recently, an important topic of major depressive disorder (MDD) had been published in 2013. MDD is one of the most prevalent and disabling mental disorders. Consequently, much research is being undertaken into the causes and treatment. It has been found that inhibition of the β form of calcium/calmodulin-dependent protein kinase type II (β-CaMKII) can ameliorate the disorder. Upon screening the traditional Chinese medicine (TCM) database by molecular docking, sengesterone, labiatic acid, and methyl 3-O-feruloylquinate were selected for molecular dynamics. After 20 ns simulation, the RMSD, total energy, and structure variation could define the protein-ligand interaction. Furthermore, sengesterone, the principle candidate compound, has been found to have an effect on the regulation of emotions and memory development. In structure variation, we find the sample functional group of important amino acids make the protein stable and have limited variation. Due to similarity of structure variations, we suggest that these compounds may have an effect on β-CaMKII and that sengesterone may have a similar efficacy as the control. However labiatic acid may be a stronger inhibitor of β-CaMKII based on the larger RMSD and variation.

Depression, anxiety-like behavior and memory impairment are associated with increased oxidative stress and inflammation in a rat model of social stress

In the present study, we have examined the behavioral and biochemical effect of induction of psychological stress using a modified version of the resident-intruder model for social stress (social defeat). At the end of the social defeat protocol, body weights, food and water intake were recorded, depression and anxiety-like behaviors as well as memory function was examined. Biochemical analysis including oxidative stress measurement, inflammatory markers and other molecular parameters, critical to behavioral effects were examined. We observed a significant decrease in the body weight in the socially defeated rats as compared to the controls. Furthermore, social defeat increased anxiety-like behavior and caused memory impairment in rats (P<0.05). Socially defeated rats made significantly more errors in long term memory tests (P<0.05) as compared to control rats. Furthermore, brain extracellular signal-regulated kinase-1/2 (ERK1/2), and an inflammatory marker, interleukin (IL)-6 were activated (P<0.05), while the protein levels of glyoxalase (GLO)-1, glutathione reductase (GSR)-1, calcium/calmodulin-dependent protein kinase type (CAMK)-IV, cAMP-response-element-binding protein (CREB) and brain-derived neurotrophic factor (BDNF) were significantly less (P<0.05) in the hippocampus, but not in the prefrontal cortex and amygdala of socially defeated rats, when compared to control rats. We suggest that social defeat stress alters ERK1/2, IL-6, GLO1, GSR1, CAMKIV, CREB, and BDNF levels in specific brain areas, leading to oxidative stress-induced anxiety–depression-like behaviors and as well as memory impairment in rats.

Cypher/ZASP Is a Novel A-kinase Anchoring Protein

PKA signaling is important for the post-translational modification of proteins, especially those in cardiomyocytes involved in cardiac excitation-contraction coupling. PKA activity is spatially and temporally regulated through compartmentalization by protein kinase A anchoring proteins. Cypher/ZASP, a member of PDZ-LIM domain protein family, is a cytoskeletal protein that forms multiprotein complexes at sarcomeric Z-lines. It has been demonstrated that Cypher/ZASP plays a pivotal structural role in the structural integrity of sarcomeres, and several of its mutations are associated with myopathies including dilated cardiomyopathy. Here we show that Cypher/ZASP, interacting specifically with the type II regulatory subunit RIIα of PKA, acted as a typical protein kinase A anchoring protein in cardiomyocytes. In addition, we show that Cypher/ZASP itself was phosphorylated at Ser(265) and Ser(296) by PKA. Furthermore, the PDZ domain of Cypher/ZASP interacted with the L-type calcium channel through its C-terminal PDZ binding motif. Expression of Cypher/ZASP facilitated PKA-mediated phosphorylation of the L-type calcium channel in vitro. Additionally, the phosphorylation of the L-type calcium channel at Ser(1928) induced by isoproterenol was impaired in neonatal Cypher/ZASP-null cardiomyocytes. Moreover, Cypher/ZASP interacted with the Ser/Thr phosphatase calcineurin, which is a phosphatase for the L-type calcium channel. Taken together, our data strongly suggest that Cypher/ZASP not only plays a structural role for the sarcomeric integrity, but is also an important sarcomeric signaling scaffold in regulating the phosphorylation of channels or contractile proteins.

Left Ventricular Radial Function Associated With Genetic Variation in the cGMP-Dependent Protein Kinase

cGMP-dependent protein kinase type I is a major mediator of cGMP signaling in the cardiovascular system. Recent studies on cardiac-specific PRKG1 knockout mice demonstrated that cGMP-dependent protein kinase type I mediates the negative inotropic effect of cGMP in the myocardium. We therefore investigated the association between left ventricular (LV) function and common polymorphisms in the PRKG1 gene in a general population. In 609 randomly selected participants (51.2% women; mean age, 48.8 years; 36.6% hypertensive) who were free from overt cardiac disease, we performed echocardiography and genotyped intronic tag single-nucleotide polymorphisms (SNPs) rs1904694, rs7897633, and rs7905063 in PRKG1. On the basis of color Doppler myocardial motion data, we calculated end-systolic longitudinal and radial deformation (strain) of the LV inferolateral wall. In multivariable-adjusted analyses accounting for confounders and relatedness, systolic radial strain was significantly (P ≤ 0.005) higher in homozygotes for rs1904694 (GG), rs7897633 (AA), and rs7905063 (TT) compared with heterozygotes or noncarriers. Haplotype analysis confirmed that LV radial strain was significantly higher in GAT homozygotes than in noncarriers (62.3% versus 56.0%; P = 0.0005). Transmission of the PRKG1 GAT haplotype to informative offspring was associated with higher LV radial strain (effect size, 6.11%; P = 0.017). For other LV phenotypes, none of the phenotype-genotype associations reached statistical significance. In conclusion, LV systolic radial function was associated with common polymorphisms in PRKG1. If experimental studies and longitudinal follow-up of LV function confirm the causality of this association, interference with cGMP-dependent protein kinase type I function might be a target for pharmacological intervention.

High glucose increases glomerular filtration barrier permeability by activating protein kinase G type Iα subunits in a Nox4-dependent manner

Hyperglycemia is a primary factor that disturbs podocyte function in the glomerular filtration process; this disturbance leads to the development of diabetic nephropathy, and ultimately, renal failure. Podocyte function may also be altered by biological agents that modify protein kinase activity, including the cGMP-activated protein kinase type Iα (PKGIα). We hypothesized that hyperglycemia-induced podocyte protein hyperpermeability was dependent on PKGIα activation, and that PKGIα was activated via dimerization induced by reactive oxygen species. This hypothesis was investigated in rat podocytes cultured in high glucose (HG, 30mM). Protein expression was measured with Western blot and immunofluorescence. Podocyte permeability was measured with a transmembrane albumin flux assay. We found that HG increased podocyte permeability in long-term incubations (1, 3, and 5 days); permeability was increased by 66% on day 5. This effect was abolished with apocynin, a NAD(P)H inhibitor, and Rp-8-Br-cGMPS, a PKG inhibitor. It was also abolished by introducing small interfering RNAs (siRNAs) against Nox4 and PKGIα into cultured podocytes. Furthermore, HG increased PKGIα dimerization by 138% (0.23±0.04 vs. 0.54±0.09; P<0.05); this effect was abolished with a siRNA against Nox4. Our observations suggested that HG could increase albumin permeability across the podocyte filtration barrier via Nox4-dependent PKGIα dimerization.

Reining in the habenula?

A new study shows that increased β-calcium/calmodulin-dependent protein kinase type II expression in the lateral habenula is both sufficient and necessary for the expression of depression-like behaviour in rodents.

Disruption of TAB1/p38α Interaction Using a Cell-permeable Peptide Limits Myocardial Ischemia/Reperfusion Injury

Targeting the adaptor protein (transforming growth factor-β (TGF-β)-activated protein kinase 1 (TAK1)-binding protein 1) (TAB1)-mediated non-canonical activation of p38α to limit ischemia/reperfusion (I/R) injury after an acute myocardial infarction seems to be attractive since TAB1/p38α interaction occurs specifically in very limited circumstances and possesses unique structural basis. However, so far no TAB1/p38α interaction inhibitor has been reported due to the limited knowledge about the interfaces. In this study, we sought to identify key amino acids essential for the unique mode of interaction with computer-guided molecular simulations and molecular docking. After validation of the predicted three-dimensional (3-D) structure of TAB1/p38α complex, we designed several peptides and evaluated whether they could block TAB1/p38α interaction with selectivity. We found that a cell-permeable peptide worked as a selective TAB1/p38α interaction inhibitor and decreased myocardial I/R injury. To our knowledge, this is the first TAB1/p38α interaction inhibitor.