The cAMP-dependent protein kinase substrate Rap1 in platelets from patients with obsessive compulsive disorder or schizophrenia

Epigenome-wide DNA methylation analysis of whole blood cells derived from patients with GAD and OCD in the Chinese Han population

Generalized anxiety disorder (GAD) and obsessive-compulsive disorder (OCD) had high comorbidity and affected more than 44 million people around the world leading to a huge burden on health and economy. Here, we conducted an epigenome-wide DNA methylation study employing 93 patients with GAD, 65 patients with OCD, and 302 health controls, to explore epigenetic alterations associated with the onset and differences of GAD and OCD. We identified multiple differentially methylated positions (DMPs) and regions (DMRs): three DMP genes included RIOK3 (cg21515243, p = 8.00 × 10^-10), DNASE2 (cg09379601, p = 1.10 × 10^-9), and PSMB4 (cg01334186, p = 3.70 × 10^-7) and two DMR genes USP6NL (p = 4.50 × 10^-4) and CPLX1 (p = 6.95 × 10^-4) were associated with the onset of GAD and OCD; three DMPs genes included LDLRAP1 (cg21400344, p = 4.40 × 10^-12), ACIN1 (cg23712970, p = 2.98×10^-11), and SCRT1 (cg25472897, p = 5.60 × 10^-11) and three DMR genes WDR19 (p = 3.39 × 10^-3), SYCP1 (p = 6.41 × 10^-3), and FAM172A (p = 5.74 × 10^-3) were associated with the differences between GAD and OCD. Investigation of epigenetic age and chronological age revealed a different epigenetic development trajectory of GAD and OCD. Conclusively, our findings which yielded robust models may aid in distinguishing patients from healthy controls (AUC = 0.90-0.99) or classifying patients with GAD and OCD (AUC = 0.89-0.99), and may power the precision medicine for them.

Long-term moderate exercise enhances specific proteins that constitute neurotrophin signaling pathway: A TMT-based quantitative proteomic analysis of rat plasma

Physical exercise has been reported to increase neurotrophin in brain tissues as hippocampus as well as increased neurotrophic level peripherally in blood plasma and might have an effect on/or affect molecular processes of energy metabolism (and homeostasis). In this study, using quantitative proteomic analysis, we obtained a plasma protein profile from the rat with long-term moderate exercise. A total of 752 proteins were identified in the plasma. Among them, 54 proteins were significant up-regulated and 47 proteins were down-regulated in the plasma of exercise group compared with the control group. Bioinformatic analyses showed that these altered proteins are widely involved in multiple biological processes, molecular functions and cellular components, which connect with 11 signaling pathways. Interestingly, 5 up-regulated proteins Rap1b, PTPN11, ARHGDIA, Cdc42 and YWHAE, confirmed by Western blots, are involved in the neurotrophin signaling pathway which shows the lowest P value among the identified pathways. Further analyses showed that the 5 neurotrophin-signaling-pathway-related proteins participate in two important protein-protein interaction networks associated to cell survival and apoptosis, axonal development, synapse formation and plasticity. This study provides an exercise-induced plasma protein profile, suggesting that long-term exercise enhances the proteins involved in neurotrophin signaling pathway which may contribute to health benefit.

SIGNIFICANCE

Physical activity contributes to myriad benefits on body health across the lifespan. The changes in plasma proteins after chronic moderate exercise may be used as biomarkers for health and may also play important roles in increase of cardiovascular fitness, enhancement of immune competence, prevention of obesity, decrease of risk for neurological disorders, cancer, stroke, diabetes and other metabolic disorders. Using a TMT-based proteomic method, this study identified 101 altered proteins in the plasma of rats after long-term moderate treadmill running, which may provide novel biomarkers for further investigation of the underlying mechanism of physical exercise. We confirmed that exercise enhances 5 proteins of the neurotrophin signaling pathway that may contribute to health benefits.

Accumulation of minor alleles and risk prediction in schizophrenia

Schizophrenia is a common neuropsychiatric disorder with a lifetime risk of 1%. Accumulation of common polygenic variations has been found to be an important risk factor. Recent studies showed a role for the enrichment of minor alleles (MAs) of SNPs in complex diseases such as Parkinson’s disease. Here we similarly studied the role of genome wide MAs in schizophrenia using public datasets. Relative to matched controls, schizophrenia cases showed higher average values in minor allele content (MAC) or the average amount of MAs per subject. By risk prediction analysis based on weighted genetic risk score (wGRS) of MAs, we identified an optimal MA set consisting of 23 238 variants that could be used to predict 3.14% of schizophrenia cases, which is comparable to using 22q11 deletion to detect schizophrenia cases. Pathway enrichment analysis of these SNPs identified 30 pathways with false discovery rate (FDR) <0.02 and of significant P-value, most of which are known to be linked with schizophrenia and other neurological disorders. These results suggest that MAs accumulation may be a risk factor to schizophrenia and provide a method to genetically screen for this disease.

Protein Kinase A and Anxiety-Related Behaviors: A Mini-Review

This review focuses on the anxiety related to cyclic AMP/protein kinase A (PKA) signaling pathway that regulates stress responses. PKA regulates an array of diverse signals that interact with various neurotransmitter systems associated with alertness, mood, and acute and social anxiety-like states. Recent mouse studies support the involvement of the PKA pathway in common neuropsychiatric disorders characterized by heightened activation of the amygdala. The amygdala is critical for adaptive responses leading to fear learning and aberrant fear memory and its heightened activation is widely thought to underpin various anxiety disorders. Stress-induced plasticity within the amygdala is involved in the transition from normal vigilance responses to emotional reactivity, fear over-generalization, and deficits in fear inhibition resulting in pathological anxiety and conditions, such as panic and depression. Human studies of PKA signaling defects also report an increased incidence of psychiatric disorders, including anxiety, depression, bipolar disorder, learning disorders, and attention deficit hyperactivity disorder. We speculate that the PKA system is uniquely suited for selective, molecularly targeted intervention that may be proven effective in anxiolytic therapy.

Proteomic analysis of the maternal protein restriction rat model for schizophrenia: identification of translational changes in hormonal signaling pathways and glutamate neurotransmission

Previous studies have found that some first onset schizophrenia patients show signs of impaired insulin signaling. Also, epidemiological studies have shown that periods of suboptimal nutrition including protein deficiencies during pregnancy can lead to increased incidence of metabolic conditions and psychiatric disorders in the offspring. For these reasons, we have carried out a molecular profiling analysis of blood serum and brain tissues from adult offspring produced by the maternal low protein (LP) rat model. The results showed similar changes to those seen in schizophrenia. Multiplex immunoassay profiling identified changes in the levels of insulin, adiponectin, and leptin along with alterations in inflammatory and vascular system-related proteins such as osteopontin, macrophage colony-stimulating factor 1, and vascular cell adhesion molecule 1. LC-MS(E) proteomic profiling showed that glutamatergic pathways were altered in frontal cortex, while signaling pathways and cytoskeletal proteins involved in hormonal secretion and synaptic remodeling were altered in the hypothalamus. Taken together, these studies indicate that the LP rat model recapitulates several pathophysiological attributes seen in schizophrenia patients. We propose that the LP model may have utility for drug discovery efforts, especially to identify compounds that modulate the metabolic and glutamatergic systems.

Social, communication, and cortical structural impairments in Epac2-deficient mice

Deficits in social and communication behaviors are common features of a number of neurodevelopmental disorders. However, the molecular and cellular substrates of these higher order brain functions are not well understood. Here we report that specific alterations in social and communication behaviors in mice occur as a result of loss of the EPAC2 gene, which encodes a protein kinase A-independent cAMP target. Epac2-deficient mice exhibited robust deficits in social interactions and ultrasonic vocalizations, but displayed normal olfaction, working and reference memory, motor abilities, anxiety, and repetitive behaviors. Epac2-deficient mice displayed abnormal columnar organization in the anterior cingulate cortex, a region implicated in social behavior in humans, but not in somatosensory cortex. In vivo two-photon imaging revealed reduced dendritic spine motility and density on cortical neurons in Epac2-deficient mice, indicating deficits at the synaptic level. Together, these findings provide novel insight into the molecular and cellular substrates of social and communication behavior.

Brain region-specific decrease in the activity and expression of protein kinase A in the frontal cortex of regressive autism

Autism is a severe neurodevelopmental disorder that is characterized by impaired language, communication, and social skills. In regressive autism, affected children first show signs of normal social and language development but eventually lose these skills and develop autistic behavior. Protein kinases are essential in G-protein-coupled, receptor-mediated signal transduction and are involved in neuronal functions, gene expression, memory, and cell differentiation. We studied the activity and expression of protein kinase A (PKA), a cyclic AMP–dependent protein kinase, in postmortem brain tissue samples from the frontal, temporal, parietal, and occipital cortices, and the cerebellum of individuals with regressive autism; autistic subjects without a clinical history of regression; and age-matched developmentally normal control subjects. The activity of PKA and the expression of PKA (C-α), a catalytic subunit of PKA, were significantly decreased in the frontal cortex of individuals with regressive autism compared to control subjects and individuals with non-regressive autism. Such changes were not observed in the cerebellum, or the cortices from the temporal, parietal, and occipital regions of the brain in subjects with regressive autism. In addition, there was no significant difference in PKA activity or expression of PKA (C-α) between non-regressive autism and control groups. These results suggest that regression in autism may be associated, in part, with decreased PKA-mediated phosphorylation of proteins and abnormalities in cellular signaling.

Ndel1 alters its conformation by sequestering cAMP-specific phosphodiesterase-4D3 (PDE4D3) in a manner that is dynamically regulated through Protein Kinase A (PKA)

The involvement of the Nuclear distribution element-like (Ndel1; Nudel) protein in the recruitment of the dynein complex is critical for neurodevelopment and potentially important for neuronal disease states. The PDE4 family of phosphodiesterases specifically degrades cAMP, an important second messenger implicated in learning and memory functions. Here we show for the first time that Ndel1 can interact directly with PDE4 family members and that the interaction of Ndel1 with the PDE4D3 isoform is uniquely disrupted by elevation of intracellular cAMP levels. While all long PDE4 isoforms are subject to stimulatory PKA phosphorylation within their conserved regulatory UCR1 domain, specificity for release of PDE4D3 is conferred due to the PKA-dependent phosphorylation of Ser13 within the isoform-specific, unique amino-terminal domain of PDE4D3. Scanning peptide array analyses identify a common region on Ndel1 for PDE4 binding and an additional region that is unique to PDE4D3. The common site lies within the stutter region that links the second coiled-coil region to the unstable third coiled-coil regions of Ndel1. The additional binding region unique to PDE4D3 penetrates into the start of the third coiled-coil region that can undergo tail-to-tail interactions between Ndel1 dimers to form a 4 helix bundle. We demonstrate Ndel1 self-interaction in living cells using a BRET approach with luciferase- and GFP-tagged forms of Ndel1. BRET assessed Ndel1-Ndel1 self-interaction is amplified through the binding of PDE4 isoforms. For PDE4D3 this effect is ablated upon elevation of intracellular cAMP due to PKA-mediated phosphorylation at Ser13, while the potentiating effects of PDE4B1 and PDE4D5 are resistant to cAMP elevation. PDE4D long isoforms and Ndel1 show a similar sub-cellular distribution in hippocampus and cortex and locate to post-synaptic densities. We show that Ndel1 sequesters EPAC, but not PKA, in order to form a cAMP signalling complex. We propose that a key function of the Ndel1 signalling scaffold is to signal through cAMP by sequestering EPAC, whose activity may thus be specifically regulated by sequestered PDE4 that also stabilizes Ndel1-Ndel1 self-interaction. In the case of PDE4D3, its association with Ndel1 is dynamically regulated by PKA input through its ability to phosphorylate Ser13 in the unique N-terminal region of this isoform, triggering the specific release of PDE4D3 from Ndel1 when cAMP levels are elevated. We propose that Ser13 may act as a redistribution trigger in PDE4D3, allowing it to dynamically re-shape cAMP gradients in distinct intracellular locales upon its phosphorylation by PKA.

Gene expression changes in peripheral mononuclear cells from schizophrenic patients treated with a combination of antipsychotic with fluvoxamine

Antipsychotic treatment combined with Selective Serotonin Reuptake Inhibitor (SSRI) antidepressant can improve negative symptoms in schizophrenic patients that are unresponsive to antipsychotic drugs alone. The mechanism of this therapeutic effect is not clear. The current study examined molecular changes induced by the combined treatment in human peripheral mononuclear cells (PMC) in order to get insight into its mechanism of action. Gene expression profile of PMC from antipsychotic-treated patients was examined before addition of the SSRI fluvoxamine, and 3 and 6 weeks after. Gene expression patterns screened with a cDNA array, comprising 1176 genes, revealed homologous changes in a range of transcripts related to G-protein coupled receptors (GPCR). Genes related to GPCR-family were assayed using customized cDNA array and the results verified by real-time RT-PCR. The mRNA expression of chemokine receptors, IL8RA and CCR1, and of RGS7 was significantly down-regulated following fluvoxamine augmentation. The clinical assessments showed improvement in negative symptoms following the combined treatment. The transcriptional analysis suggests that the therapeutic mechanism of the combined antipsychotic-fluvoxamine treatment may involve genes associated with G-protein coupled receptors (GPCR). Our findings suggest that gene expression changes in PMC may be useful in investigating the mechanism of drug action in schizophrenia.

Platelet resistance to the antiaggregatory cyclic nucleotides in central obesity involves reduced phosphorylation of vasodilator-stimulated phosphoprotein

BACKGROUND

Impairment of platelet response to antiaggregatory agents is seen in individuals with central obesity and may play a role in the increased cardiovascular risk associated with obesity. In this study we evaluated whether this impairment involves the antiaggregatory pathways regulated by cAMP and cGMP.

METHODS

We obtained platelet-rich plasma from 12 obese individuals and 12 controls. We investigated the effects of the cyclic nucleotide analogs 8-pCPT-cAMP (10-500 micromol/L) and 8-pCPT-cGMP (10-500 micromol/L) on ADP-induced platelet aggregation as assessed by decreased light scattering. We assessed the activation of cAMP- and cGMP-dependent protein kinases by measuring phosphorylation of the vasodilator-stimulated phosphoprotein (VASP) at Ser157 and Ser239.

RESULTS

The antiaggregatory effect of both cyclic nucleotide analogs was impaired in obese individuals compared to controls, with mean (SE) half-maximal inhibitory concentrations (IC(50)) (after 20-min incubation) of 123 (33) micromol/L vs 5 (1) micromol/L, respectively, for 8-pCPT-cAMP (P <0.01) and of 172 (43) micromol/L vs 17 (8) micromol/L, respectively, for 8-pCPT-cGMP (P <0.01). The Homeostasis Model Assessment Index of Insulin Resistance was independently correlated with cyclic nucleotide analog IC(50). In obese individuals, VASP phosphorylation at Ser157 and Ser239 in response to cyclic nucleotides was significantly lower than in controls.

CONCLUSIONS

In central obesity the reduced ability of cyclic nucleotides to inhibit platelet aggregation is associated with reduced activation of their specific kinases. Because cyclic nucleotides help regulate platelet antiaggregation, alteration of this ability is consistent with platelet hyperactivity in obesity.

Rolipram attenuates MK-801-induced deficits in latent inhibition

Latent inhibition is used to examine attention and study cognitive deficits associated with schizophrenia. Research using MK-801, an N-methyl-D-aspartate (NMDA) open channel blocker, implicates glutamate receptors in acquisition of latent inhibition of cued fear conditioning. Evidence suggests an important relationship between NMDA-induced increases in cyclic adenosine monophosphate (cAMP) and learning and memory. The authors examine whether amplification of the cAMP signaling pathway by rolipram, a selective Type 4 cAMP phosphodiesterase inhibitor, reverses MK-801-induced impairments in latent inhibition. One day before training, mice were injected with MK-801, rolipram, MK-801 and rolipram, or vehicle and received 20 preexposures or no preexposures to an auditory conditioned stimulus (CS). Training consisted of 2 CS-footshock unconditioned stimulus pairings. Rolipram attenuated the disruptive effect of MK-801 on latent inhibition, which suggests a role for the cAMP signaling pathway in the task and implicates phosphodiesterase inhibition as a target for treating cognitive impairments associated with schizophrenia.