Mutation analysis of the seven in absentia homolog 1 (SIAH1) gene in Parkinson’s disease

Targeting α-synuclein post-translational modifications in Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disease characterized by the progressive loss of dopaminergic neurons in the nigrostriatal pathway. Although the exact mechanisms underlying PD are still not completely understood, it is well accepted that α-synuclein plays key pathophysiological roles as the main constituent of the cytoplasmic inclusions known as Lewy bodies. Several post-translational modifications (PTMs), such as the best-known phosphorylation, target α-synuclein and are thus implicated in its physiological and pathological functions. In this review, we present (1) an overview of the pathophysiological roles of α-synuclein, (2) a descriptive analysis of α-synuclein PTMs, including phosphorylation, ubiquitination, SUMOylation, acetylation, glycation, truncation, and O-GlcNAcylation, as well as (3) a brief summary on α-synuclein PTMs as potential biomarkers for PD. A better understanding of α-synuclein PTMs is of paramount importance for elucidating the mechanisms underlying PD and can thus be expected to improve early detection and monitoring disease progression, as well as identify promising new therapeutic targets.

MicroRNA-193b-3p reduces oxidative stress and mitochondrial damage in rats with cerebral ischemia-reperfusion injury via the seven in absentia homolog 1/Jun N-terminal kinase pathway

Ischemic stroke is one of the major causes of death and disability among adults. This study sought to explore the mechanism of microRNA (miR)-193b-3p in rats with cerebral ischemia-reperfusion (I/R) injury. The cerebral I/R injury models of rats were established using the suture-occluded method. The pathological changes were observed, and oxidative stress (OS) and mitochondrial function indexes in rat brain tissue were examined. The levels of miR-193b-3p and seven in absentia homolog 1 (SIAH1) were detected. miR-193b-3p agomir or antagomir was injected into the lateral ventricle of I/R rats to overexpress or inhibit miR-193b-3p expression. The targeting relationship between miR-193b-3p and SIAH1 was verified. The effect of SIAH1 overexpression on brain injury in I/R rats was investigated by injecting the lentivirus vector into the lateral ventricle. The phosphorylation level of Jun N-terminal kinase (JNK) was identified. miR-193b-3p was lowly expressed in I/R rats. Overexpression of miR-193b-3p alleviated the pathological damage of I/R rats and limited the OS and mitochondrial damage. miR-193b-3p targeted SIAH1. Overexpression of SIAH1 partially reversed the protection of miR-193b-3p overexpression against cerebral I/R injury. p-JNK was up-regulated in I/R rats and overexpression of miR-193b-3p inhibited p-JNK. Overall, overexpression of miR-193b-3p targeted SIAH1 to inhibit the activation of the JNK pathway and protect rats against cerebral I/R injury.

Siah1 in cancer and nervous system diseases (Review)

The dysregulation of the ubiquitin‑proteasome system will result in the abnormal accumulation and dysfunction of proteins, thus leading to severe diseases. Seven in absentia homolog 1 (Siah1), an E3 ubiquitin ligase, has attracted wide attention due to its varied functions in physiological and pathological conditions, and the numerous newly discovered Siah1 substrates. In cancer and nervous system diseases, the functions of Siah1 as a promoter or a suppressor of diseases are related to the change in cellular microenvironment and subcellular localization. At the same time, complex upstream regulations make Siah1 different from other E3 ubiquitin ligases. Understanding the molecular mechanism of Siah1 will help the study of various signaling pathways and benefit the therapeutic strategy of human diseases (e.g., cancer and nervous system diseases). In the present review, the functions and regulations of Siah1 are described. Moreover, novel substrates of Siah1 discovered in recent studies will be highlighted in cancer and nervous system diseases, providing ideas for future research and clinical targeted therapies using Siah1.

Tuberculosis comorbidity with rheumatoid arthritis: Gene signatures, associated biomarkers, and screening

Rheumatoid arthritis (RA) is known to be related to an elevated risk of infections because of its pathobiology and the use of immunosuppressive therapies. Reactivation of latent tuberculosis (TB) infection is a serious issue in patients with RA, especially after receiving anti-TNFs therapy. TNF blocking reinforces the TB granuloma formation and maintenance and the growth of Mycobacterium tuberculosis (Mtb). After intercurrent of TB infection, the standard recommendation is that the treatment with TNF inhibitors to be withheld despite its impressive effect on suppression of inflammation until the infection has resolved. Knowing pathways and mechanisms that are common between two diseases might help to find the mechanistic basis of this comorbidity, as well as provide us a new approach to apply them as therapeutic targets or diagnostic biomarkers. Also, screening for latent TB before initiation of an anti-TNF therapy can minimize complications. This review summarizes the shared gene signature between TB and RA and discusses the biomarkers for early detection of this infection, and screening procedures as well.

Genome-Wide Identification of Apple Ubiquitin SINA E3 Ligase and Functional Characterization of MdSINA2

SINA (Seven in absentia) proteins are a small family of ubiquitin ligases that play important roles in regulating plant growth and developmental processes as well as in responses to diverse types of biotic and abiotic stress. However, the characteristics of the apple SINA family have not been previously studied. Here, we identified 11 MdSINAs members in the apple genome based on their conserved, N-terminal RING and C-terminal SINA domains. We also reconstructed a phylogeny of these genes; characterized their chromosomal location, structure, and motifs; and identified two major groups of MdSINA genes. Subsequent qRT-PCR analyses were used to characterize the expression of MdSINA genes in various tissues and organs, and levels of expression were highest in leaves. MdSINAs were significantly induced under ABA and carbon- and nitrate-starvation treatment. Except for MdSINA1 and MdSINA7, the other MdSINA proteins could interact with each other. Moreover, MdSINA2 was found to be localized in the nucleus using Agrobacterium-mediated transient expression. Western-blot analysis showed that MdSINA2 accumulated extensively under light, decreased under darkness, and became insensitive to light when the RING domain was disrupted. Finally, ABA-hypersensitive phenotypes were confirmed by transgenic calli and the ectopic expression of MdSINA2 in Arabidopsis. In conclusion, our results suggest that MdSINA genes participate in the responses to different types of stress, and that MdSINA2 might act as a negative regulator in the ABA stress response.

Transcriptome-wide association study of inflammatory biologic age

Chronic low grade inflammation is a fundamental mechanism of aging. We estimated biologic age using nine biomarkers from diverse inflammatory pathways and we hypothesized that genes associated with inflammatory biological age would provide insights into human aging. In Framingham Offspring Study participants at examination 8 (2005 to 2008), we used the Klemera-Doubal method to estimate inflammatory biologic age and we computed the difference (∆Age) between biologic age and chronologic age. Gene expression in whole blood was measured using the Affymetrix Human Exon 1.0 ST Array. We used linear mixed effect models to test associations between inflammatory ∆Age and gene expression (dependent variable) adjusting for age, sex, imputed cell counts, and technical covariates. Our study sample included 2386 participants (mean age 67A±9 years, 55% women). There were 448 genes significantly were associated with inflammatory ∆Age (P<2.8x10^-6), 302 genes were positively associated and 146 genes were negatively associated. Pathway analysis among the identified genes highlighted the NOD-like receptor signaling and ubiquitin mediated proteolysis pathways. In summary, we identified 448 genes that were significantly associated with inflammatory biologic age. Future functional characterization may identify molecular interventions to delay aging and prolong healthspan in older adults.

E3 Ubiquitin Ligase Siah-1 is Down-regulated and Fails to Target Natural HBx Truncates for Degradation in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is a common worldwide malignancy with high morbidity and mortality. Hepatitis B viral (HBV)-encoded X protein (HBx) and natural HBx variants play important roles in HBV-associated HCC development. HBx is an unstable protein that can be degraded in vivo. Our previous study found that the E3 ubiquitin ligase Siah-1 could target HBx for poly-ubiquitylation and proteasomal degradation and attenuate the transcriptional activity of HBx. However, in HCC patients, high expression levels of HBx and HBx variants are frequently observed and are associated with HCC progression. The mechanism underlying their up-regulation is largely unknown. In this study, we screened for Siah-1 mutations in 270 HCC samples and 9 HCC cell lines, and examined Siah-1 mRNA and protein expression in a subset of paired HCC specimens. Our results demonstrate that Siah-1 is highly conserved, as no somatic mutation was identified, with the exception of one synonymous transition from G to A at codon 67. Both the mRNA and protein levels of Siah-1 were significantly down-regulated in HCC tissues compared with their adjacent normal counterparts. We constructed three natural HBx truncates that were identified in our HCC cases. We found that Siah-1 failed to decrease the stability of these HBx variants and was unable to inhibit the transcriptional activity of these HBx truncates at heat shock elements (HSEs). Moreover, Siah-1 had weaker association with three HBx mutants than full length HBx. Therefore, our findings suggest that down-regulation of Siah-1, but not its mutations, and natural HBx variants resistant to Siah-1-induced degradation may be a novel mechanism for HCC development.

α-Synuclein aggregation and modulating factors

Aggregated a-synuclein is the major component of inclusions in Parkinson's disease and other synucleinopathy brains indicating that a-syn aggregation is associated with the pathogenesis of neurodegenerative disorders. Although the mechanisms underlying a-syn aggregation and toxicity are not fully elucidated, it is clear that a-syn undergoes post-translational modifications and interacts with numerous proteins and other macromolecules, metals, hormones, neurotransmitters, drugs and poisons that can all modulate its aggregation propensity. The current and most recent findings regarding the factors modulating a-syn aggregation process are discussed in detail.

Ubiquitination of LHY by SINAT5 regulates flowering time and is inhibited by DET1

Ubiquitin is a small polypeptide and ubiquitination is the post-translational modification by ubiquitin protein, resulting in degradation of target proteins by the 26S proteasome complex. Here, we found that E3 ubiquitin ligase SINAT5, an Arabidopsis homologue of the Drosophila SINA RING-finger protein, interacts directly with LHY, a component of the circadian oscillator, and DET1, a negative regulator of light-regulated gene expression. We also found that SINAT5 has E3 ubiquitination activity for LHY but not for DET1. Interestingly, LHY ubiquitination by SINAT5 was inhibited by DET1. Late flowering of sinat5 mutants indicates that flowering time can be controlled by DET1 through regulation of LHY stability by SINAT5.

Seven in absentia proteins affect plant growth and nodulation in Medicago truncatula

Protein ubiquitination is a posttranslational regulatory process essential for plant growth and interaction with the environment. E3 ligases, to which the seven in absentia (SINA) proteins belong, determine the specificity by selecting the target proteins for ubiquitination. SINA proteins are found in animals as well as in plants, and a small gene family with highly related members has been identified in the genome of rice (Oryza sativa), Arabidopsis (Arabidopsis thaliana), Medicago truncatula, and poplar (Populus trichocarpa). To acquire insight into the function of SINA proteins in nodulation, a dominant negative form of the Arabidopsis SINAT5 was ectopically expressed in the model legume M. truncatula. After rhizobial inoculation of the 35S:SINAT5DN transgenic plants, fewer nodules were formed than in control plants, and most nodules remained small and white, a sign of impaired symbiosis. Defects in rhizobial infection and symbiosome formation were observed by extensive microscopic analysis. Besides the nodulation phenotype, transgenic plants were affected in shoot growth, leaf size, and lateral root number. This work illustrates a function for SINA E3 ligases in a broad spectrum of plant developmental processes, including nodulation.