NMDA receptor signaling mediates the expression of protein inhibitor of activated STAT1 (PIAS1) in rat hippocampus

IL-17 promotes melanoma through TRAF2 as a scaffold protein recruiting PIAS2 and ELAVL1 to induce EPHA5

An abnormal immune response induces melanoma development. IL-17 and the classical downstream signal STAT1 are associated with melanoma development. TRAF2 also mediates the downstream signaling of IL-17; however, its role in IL-17-stimulated melanoma remains unclear. Bioinformatic analysis revealed that TRAF2 can bind to PIAS2 (a SUMO E3 ligase), ELAVL1 (an RNA-binding protein), and EPHA5 (an ephrin receptor of the tyrosine kinase family). To elucidate the IL-17 downstream signal, the IL-17 receptor (R), STAT1, TRAF2, PIAS2, ELAVL1, and EPHA5 were knocked down before melanoma cells were treated with recombinant IL-17A protein. Co-immunoprecipitation and RNA immunoprecipitation were conducted to determine the interaction of TRAF2 with PIAS2, ELAVL1, and EPHA5 proteins, as well as the interaction of ELAVL1 protein with EPHA5 mRNA. STAT1 knockdown suppressed the proliferation and invasion triggered by IL-17A, but the suppressive effects were much weaker than those caused by IL-17R knockdown. This implies that another nonclassical signal mediates IL-17 effects. IL-17A induces TRAF2 recruitment of ELAVL1, PIAS2, and EPHA5 proteins. We speculated that ELAVL1 bound to the AU-rich elements in the 3' untranslated region of the EPHA5 mRNA, thereby enhancing mRNA stability. Furthermore, PIAS2 induced EPHA5 SUMOylation, which suppressed EPHA5 ubiquitination and degradation. Through pre- and post-translational regulation, IL-17A induced EPHA5 expression in melanoma, and EPHA5 knockdown markedly suppressed IL-17A-induced proliferation and invasion. This study revealed a non-classical signaling mechanism responsible for the effects of IL-17 in melanoma.

Super-resolution study of PIAS SUMO E3-ligases in hippocampal and cortical neurons

The SUMOylation machinery is a regulator of neuronal activity and synaptic plasticity. It is composed of SUMO isoforms and specialized enzymes named E1, E2 and E3 SUMO ligases. Recent studies have highlighted how SUMO isoforms and E2 enzymes localize with synaptic markers to support previous functional studies but less information is available on E3 ligases. PIAS proteins - belonging to the protein inhibitor of activated STAT (PIAS) SUMO E3-ligase family - are the best-characterized SUMO E3-ligases and have been linked to the formation of spatial memory in rodents. Whether however they exert their function co-localizing with synaptic markers is still unclear. In this study, we applied for the first time structured illumination microscopy (SIM) to PIAS ligases to investigate the co-localization of PIAS1 and PIAS3 with synaptic markers in hippocampal and cortical murine neurons. The results indicate partial co-localization of PIAS1 and PIAS3 with synaptic markers in hippocampal neurons and much rarer occurrence in cortical neurons. This is in line with previous super-resolution reports describing the co-localization with synaptic markers of other components of the SUMOylation machinery.

Genes in immune pathways associated with abnormal white matter integrity in first-episode and treatment-naïve patients with schizophrenia

BACKGROUND

Previous studies have inferred a strong genetic component in schizophrenia. However, the genetic variants involved in the susceptibility to schizophrenia remain unclear.AimsTo detect potential gene pathways and networks associated with schizophrenia, and to explore the relationship between common and rare variants in these pathways and abnormal white matter integrity in schizophrenia.

METHOD

The analysis included 100 first-episode treatment-naïve patients with schizophrenia and 140 healthy controls. A network-based analysis was carried out on the data collected from the Psychiatric Genomics Consortium Phase I (PGC-I). Based on our genome-wide association study and whole-exome sequencing data-sets, we performed a gene-set analysis to detect associations between the combining effects of common and rare genetic variants and abnormal white matter integrity in schizophrenia.

RESULTS

Patients had significantly reduced functional anisotropy in the left and right anterior cingulate cortex, left and right precuneus and extra-nuclear (t = 4.61-5.10, PFDR < 0.01), compared with controls. Generated from co-expression network analysis of the PGC-1 summary statistics of schizophrenia, a subnetwork of 207 genes associated with schizophrenia was identified (P < 0.01), and 176 genes were co-expressed in four gene modules. Functional enrichment analysis for genes in each module revealed that the yellow module was enriched with highly co-expressed, innate immune response genes. Furthermore, rare variants of enriched genes in the yellow module were associated with reduced functional anisotropy in the left anterior cingulate cortex (P = 0.006; Padjusted = 0.024) in patients only.

CONCLUSIONS

The pathogenesis of schizophrenia may be substantially influenced by genes involved in the immune system, via both pathway and network.Declaration of interestsNone.

Smad4 SUMOylation is essential for memory formation through upregulation of the skeletal myopathy gene TPM2

Background

Smad4 is a critical effector of TGF-β signaling that regulates a variety of cellular functions. However, its role in the brain has rarely been studied. Here, we examined the molecular mechanisms underlying the post-translational regulation of Smad4 function by SUMOylation, and its role in spatial memory formation.

Results

In the hippocampus, Smad4 is SUMOylated by the E3 ligase PIAS1 at Lys-113 and Lys-159. Both spatial training and NMDA injection enhanced Smad4 SUMOylation. Inhibition of Smad4 SUMOylation impaired spatial learning and memory in rats by downregulating TPM2, a gene associated with skeletal myopathies. Similarly, knockdown of TPM2 expression impaired spatial learning and memory, while TPM2 mRNA and protein expression increased after spatial training. Among the TPM2 mutations associated with skeletal myopathies, the TPM2E122K mutation was found to reduce TPM2 expression and impair spatial learning and memory in rats.

Conclusions

We have identified a novel role of Smad4 SUMOylation and TPM2 in learning and memory formation. These results suggest that patients with skeletal myopathies who carry the TPM2E122K mutation may also have deficits in learning and memory functions.

Electronic supplementary material

The online version of this article (doi:10.1186/s12915-017-0452-9) contains supplementary material, which is available to authorized users.

Epigenetic regulation of HDAC1 SUMOylation as an endogenous neuroprotection against Aβ toxicity in a mouse model of Alzheimer's disease

Amyloid-β (Aβ) produces neurotoxicity in the brain and causes neuronal death, but the endogenous defense mechanism that is activated on Aβ insult is less well known. Here we found that acute Aβ increases the expression of PIAS1 and Mcl-1 via activation of MAPK/ERK, and Aβ induction of PIAS1 enhances HDAC1 SUMOylation in rat hippocampus. Knockdown of PIAS1 decreases endogenous HDAC1 SUMOylation and blocks Aβ induction of Mcl-1. Sumoylated HDAC1 reduces it association with CREB, increases CREB binding to the Mcl-1 promoter and mediates Aβ induction of Mcl-1 expression. Transduction of SUMO-modified lenti-HDAC1 vector to the hippocampus of APP/PS1 mice rescues spatial learning and memory deficit and long-term potentiation impairment in APP/PS1 mice. It also reduces the amount of amyloid plaque and the number of apoptotic cells in CA1 area of APP/PS1 mice. Meanwhile, HDAC1 SUMOylation decreases HDAC1 binding to the neprilysin promoter. These results together reveal an important role of HDAC1 SUMOylation as a naturally occurring defense mechanism protecting against Aβ toxicity and provide an alternative therapeutic strategy against AD.

Hepatitis B virus surface protein-induced hPIAS1 transcription requires TAL1, E47, MYOG, NFI, and MAPK signal pathways

The protein inhibitor of activated STAT1 (PIAS1) plays important roles in regulating virus-induced chronic hepatitis, but the interaction between hepatitis B virus (HBV) and hPIAS1 is not clear. Our aim was to verify if HBV encoding proteins enhance the transcription of hPIAS1 and which cis-elements and transcription factors were involved in the mechanism. In order to do, so a series of molecular biological methods, along with functional and histological studies, were performed. We found that the HBV surface protein (HBs) enhanced hPIAS1 transcription through the activities of TAL1, E47, myogenin (MYOG), and NFI, dependent on the activation of p38MAPK and ERK signaling pathways in vitro, which might contribute to the ineffectiveness of treatment in CHB patients. Furthermore, liver samples from patients with high HBsAg levels and HBV DNA displayed increased hPIAS1 expression and high levels of TAL1, E47, MYOG, and NFI, compared to those patients with low HBsAg levels and HBV DNA, and healthy controls. These findings suggest that the HBs protein-induced hPIAS1 transcription requires TAL1, E47, MYOG, NFI, and MAPK signal pathways. It provides new potential targets for antiviral therapeutic strategies for controlling HBV-associated diseases.

CREB SUMOylation by the E3 ligase PIAS1 enhances spatial memory

cAMP-responsive element binding protein (CREB) phosphorylation and signaling plays an important role in long-term memory formation, but other posttranslational modifications of CREB are less known. Here, we found that CREB1Δ, the short isoform of CREB, could be sumoylated by the small ubiquitin-like modifier (SUMO) E3 ligase protein inhibitor of activated STAT1 (PIAS1) at Lys271 and Lys290 and PIAS1 SUMOylation of CREB1Δ increased the expression level of CREB1Δ. CREB1Δ could also be sumoylated by other PIAS family proteins, but not by the E3 ligases RanBP2 and Pc2 or by the E2 ligase Ubc9. Furthermore, water maze training increased the level of endogenous CREB SUMOylation in rat CA1 neurons determined by in vitro SUMOylation assay, but this effect was not observed in other brain areas. Moreover, transduction of Lenti-CREBWT to rat CA1 area facilitated, whereas transduction of Lenti-CREB double sumo-mutant (CREBK271RK290R) impaired, spatial learning and memory performance. Transduction of Lenti-CREBWT-SUMO1 fusion vector to rat CA1 area showed a more significant effect in enhancing spatial learning and memory and CREB SUMOylation. Lenti-CREBWT transduction increased, whereas Lenti-CREBK271RK290R transduction decreased, CREB DNA binding to the brain-derived neurotrophic factor (bdnf) promoter and decreased bdnf mRNA expression. Knock-down of PIAS1 expression in CA1 area by PIAS1 siRNA transfection impaired spatial learning and memory and decreased endogenous CREB SUMOylation. In addition, CREB SUMOylation was CREB phosphorylation dependent and lasted longer. Therefore, CREB phosphorylation may be responsible for signal transduction during the early phase of long-term memory formation, whereas CREB SUMOylation sustains long-term memory.