Post-translational modification of the RhoGTPase activating protein 21, ARHGAP21, by SUMO2/3

Association analysis of polymorphisms of candidate genes for laying traits in Yangzhou geese

Egg production is an important economic trait in the Chinese goose industry. Due to the low heritability of annual egg production traits in geese, large-scale individual selection based on annual egg production measurements cannot be carried out. Therefore, new selection methods must be applied for large-scale early selections. To screen for effective molecular markers for early Yangzhou geese selection, the genotypes and gene frequencies of mutated loci of five candidate genes related to egg production, MAGI-1, ACSF2, ASTN2, KIAA1462, and ARHGAP21, were detected and analyzed by PCR-direct sequencing.Furthermore, correlation analysis was performed with annual egg mass and body weight at the point of lay and egg weight, and the results were as follows:Magi-1 (Record-106975)was A > G, ACSF2 (Record-106582)was A > C, ASTN2 (Record-111407)was A > T, KIAA1462 (Record-134172)was A > T, and the base of ARHGAP21 (Record-112359) was G > T. At all the five loci above, the Yangzhou geese population followed the Hardy-Weinberg equilibrium (P > 0.05). The results of the association analysis between different genotypes and production performance showed no significant differences in annual egg production, body weight at the point of lay, and egg weight, among different genotypes (P > 0.05) at the mutation loci of MAGI-1 and ASTN2. At the ACSF2 and KIAA1462, the annual egg production of AC was significantly higher than that of AA and CC (P < 0.05), the annual egg production of TT was significantly higher than that of AA (P < 0.05), and there were no significant differences in body weight at the point of lay and egg weight, among the three genotypes (P > 0.05). At ARHGAP21, the body weight at the lay point of the TT genotype was the highest, which was significantly higher than that of GG (P < 0.05); however, there was no significant difference with the heterozygous GT genotype for this trait (P > 0.05). Therefore, Genotype AC at ACSF2 and genotype TT at KIAA1462 could be used as favorable genotypes for egg production, and genotype TT at ARHGAP21 could be used as a favorable genotype for weight in Yangzhou geese.

Migration deficits of the neural crest caused by CXADR triplication in a human Down syndrome stem cell model

Down syndrome (DS) is the most common chromosomal abnormality in live-born infants and is caused by trisomy of chromosome 21. Most individuals with DS display craniofacial dysmorphology, including reduced sizes of the skull, maxilla, and mandible. However, the underlying pathogenesis remains largely unknown. Since the craniofacial skeleton is mainly formed by the neural crest, whether neural crest developmental defects are involved in the craniofacial anomalies of individuals with DS needs to be investigated. Here, we successfully derived DS-specific human induced pluripotent stem cells (hiPSCs) using a Sendai virus vector. When DS-hiPSCs were induced to differentiate into the neural crest, we found that trisomy 21 (T21) did not influence cell proliferation or apoptosis. However, the migratory ability of differentiated cells was significantly compromised, thus resulting in a substantially lower number of postmigratory cranial neural crest stem cells (NCSCs) in the DS group than in the control group. We further discovered that the migration defects could be partially attributed to the triplication of the coxsackievirus and adenovirus receptor gene (CXADR; an adhesion protein) in the DS group cells, since knockdown of CXADR substantially recovered the cell migratory ability and generation of postmigratory NCSCs in the DS group. Thus, the migratory deficits of neural crest cells may be an underlying cause of craniofacial dysmorphology in individuals with DS, which may suggest potential targets for therapeutic intervention to ameliorate craniofacial or other neural crest-related anomalies in DS.

ARHGAP10 inhibits the epithelial-mesenchymal transition of non-small cell lung cancer by inactivating PI3K/Akt/GSK3β signaling pathway

Background

Rho GTPase activating protein 10 (ARHGAP10) has been implicated as an essential element in multiple cellular process, including cell migration, adhesion and actin cytoskeleton dynamic reorganization. However, the correlation of ARHGAP10 expression with epithelial–mesenchymal transition (EMT) in lung cancer cells is unclear and remains to be elucidated. Herein, we investigated the relationship between the trait of ARHGAP10 and non-small cell lung cancer (NSCLC) pathological process.

Methods

Immunohistochemistry was conducted to evaluate the expression of ARHGAP10 in NSCLC tissues. CCK-8 assays, Transwell assays, scratch assays were applied to assess cell proliferation, invasion and migration. The expression levels of EMT biomarkers and active molecules involved in PI3K/Akt/GSK3β signaling pathway were examined through immunofluorescence and Western blot.

Results

ARHGAP10 was detected to be lower expression in NSCLC tissues compared with normal tissues from individuals. Moreover, overexpression of ARHGAP10 inhibited migratory and invasive potentials of A549 and NCI-H1299 cells. In addition, ARHGAP10 directly mediated the process of EMT via PI3K/Akt/GSK3β pathway. Meanwhile, activation of the signaling pathway of insulin-like growth factors-1 (IGF-1) reversed ARHGAP10 overexpression regulated EMT in NSCLC cells.

Conclusion

ARHGAP10 inhibits the epithelial–mesenchymal transition in NSCLC via PI3K/Akt/GSK3β signaling pathway, suggesting agonist of ARHGAP10 may be an optional remedy for NSCLC patients than traditional opioids.

Whole body ARHGAP21 reduction improves glucose homeostasis in high-fat diet obese mice

GTPase activating proteins (GAPs) are ubiquitously expressed, and their role in cellular adhesion and membrane traffic processes have been well described. TBC1D1, which is a Rab-GAP, is necessary for adequate glucose uptake by muscle cells, whereas increased TCGAP, which is a Rho-GAP, decreases GLUT4 translocation, and consequently glucose uptake in adipocytes. Here, we assessed the possible involvement of ARHGAP21, a Rho-GAP protein, in glucose homeostasis. For this purpose, wild type mice and ARHGAP21 transgenic whole-body gene-deficiency mice (heterozygous mice, expressing approximately 50% of ARHGAP21) were fed either chow (Ctl and Het) or high-fat diet (Ctl-HFD and Het-HFD). Het-HFD mice showed a reduction in white fat storage, reflected in a lower body weight gain. These mice also displayed an improvement in insulin sensitivity and glucose tolerance, which likely contributed to reduced insulin secretion and pancreatic beta cell area. The reduction of body weight was also observed in Het mice and this phenomenon was associated with an increase in brown adipose tissue and reduced muscle weight, without alteration in glucose-insulin homeostasis. In conclusion, the whole body ARHGAP21 reduction improved glucose homeostasis and protected against diet-induced obesity specifically in Het-HFD mice. However, the mechanism by which ARHGAP21 leads to these outcomes requires further investigation.

SUMOylation of HSP27 by small ubiquitin-like modifier 2/3 promotes proliferation and invasion of hepatocellular carcinoma cells

Primary hepatocellular carcinoma (PHC) is a major health problem worldwide and is one of the 10 most commonly diagnosed cancers in China. Heat shock protein 27 (HSP27) were found to be overexpressed in a wide range of malignancies including PHC, however, post-translational modification of HSP27 still needs exploration in PHC. Recently, SUMOylation, an important post-translational modification associating with the development of many kinds of cancers has been intensively studied. In the current study, mRNA and protein level of HSP27 in archived tumor samples representing various pathological characteristics of PHC were examined, and modification of HSP27 by SUMO2/3 was investigated. HSP27 were expressed abundantly in patients' tumor tissues, and found to be associated with pathological progression. Besides, HSP27 was also elevated significantly in liver cancer cell lines Huh7 and HepG2 compared with human hepatocyte cells L02. Furthermore, knockdown of HSP27 was found to be associated with the decreased proliferation and invasion ability in Huh7 and HepG2 cells. Immunofluorescence assay showed that HSP27 and SUMO2/3 were co-localized in the subcellular, and co-immunoprecipitation verified the interaction between HSP27 and SUMO2/3. Overexpression of SUMO2/3 upregulated the HSP27 protein level and promotes Huh7 and HepG2 cell proliferation and invasion, and vice versa when the SUMO2/3 was knockdown. Taken together, increased protein level of HSP27 through SUMO2/3-mediated SUMOylation plays crucial roles in the progression of PHC, and this finding may shed light on developing potential therapeutic targets for PHC.

Deciphering the Molecular and Functional Basis of RHOGAP Family Proteins: A SYSTEMATIC APPROACH TOWARD SELECTIVE INACTIVATION OF RHO FAMILY PROTEINS

RHO GTPase-activating proteins (RHOGAPs) are one of the major classes of regulators of the RHO-related protein family that are crucial in many cellular processes, motility, contractility, growth, differentiation, and development. Using database searches, we extracted 66 distinct human RHOGAPs, from which 57 have a common catalytic domain capable of terminating RHO protein signaling by stimulating the slow intrinsic GTP hydrolysis (GTPase) reaction. The specificity of the majority of the members of RHOGAP family is largely uncharacterized. Here, we comprehensively investigated the sequence-structure-function relationship between RHOGAPs and RHO proteins by combining our in vitro data with in silico data. The activity of 14 representatives of the RHOGAP family toward 12 RHO family proteins was determined in real time. We identified and structurally verified hot spots in the interface between RHOGAPs and RHO proteins as critical determinants for binding and catalysis. We have found that the RHOGAP domain itself is nonselective and in some cases rather inefficient under cell-free conditions. Thus, we propose that other domains of RHOGAPs confer substrate specificity and fine-tune their catalytic efficiency in cells.

DNA methylation in the pathophysiology of hyperphenylalaninemia in the PAH(enu2) mouse model of phenylketonuria

Phenylalanine hydroxylase deficient phenylketonuria (PKU) is the paradigm for a treatable inborn error of metabolism where maintaining plasma phenylalanine (Phe) in the therapeutic range relates to improved clinical outcomes. While Phe is the presumed intoxicating analyte causal in neurologic damage, the mechanism(s) of Phe toxicity has remained elusive. Altered DNA methylation is a recognized response associated with exposure to numerous small molecule toxic agents. Paralleling this effect, we hypothesized that chronic Phe over-exposure in the brain would lead to aberrant DNA methylation with secondary influence upon gene regulation that would ultimately contribute to PKU neuropathology. The PAH(enu2) mouse models human PKU with intrinsic hyperphenylalaninemia, abnormal response to Phe challenge, and neurologic deficit. To examine this hypothesis, we assessed DNA methylation patterns in brain tissues using methylated DNA immunoprecipitation and paired end sequencing in adult PAH(enu2) animals maintained under either continuous dietary Phe restriction or chronic hyperphenylalaninemia. Heterozygous PAH(enu2/WT) litter mates served as controls for normal Phe exposure. Extensive repatterning of DNA methylation was observed in brain tissue of hyperphenylalaninemic animals while Phe restricted animals displayed an attenuated pattern of aberrant DNA methylation. Affected gene coding regions displayed aberrant hypermethylation and hypomethylation. Gene body methylation of noncoding RNA genes was observed and among these microRNA genes were prominent. Of particular note, observed only in hyperphenylalaninemic animals, was hypomethylation of miRNA genes within the imprinted Dlk1-Dio3 locus on chromosome 12. Aberrant methylation of microRNA genes influenced their expression which has secondary effects upon the expression of targeted protein coding genes. Differential hypermethylation of gene promoters was exclusive to hyperphenylalaninemic PAH(enu2) animals. Genes with synaptic involvement were targets of promoter hypermethylation that resulted in down-regulation of their expression. Gene dysregulation secondary to abnormal DNA methylation may be contributing to PKU neuropathology. These results suggest drugs that prevent or correct aberrant DNA methylation may offer a novel therapeutic option to management of neurological symptoms in PKU patients.

Regulating Rho GTPases and their regulators

Rho GTPases regulate cytoskeletal and cell adhesion dynamics and thereby coordinate a wide range of cellular processes, including cell migration, cell polarity and cell cycle progression. Most Rho GTPases cycle between a GTP-bound active conformation and a GDP-bound inactive conformation to regulate their ability to activate effector proteins and to elicit cellular responses. However, it has become apparent that Rho GTPases are regulated by post-translational modifications and the formation of specific protein complexes, in addition to GTP-GDP cycling. The canonical regulators of Rho GTPases - guanine nucleotide exchange factors, GTPase-activating proteins and guanine nucleotide dissociation inhibitors - are regulated similarly, creating a complex network of interactions to determine the precise spatiotemporal activation of Rho GTPases.

Stathmin 1 is involved in the highly proliferative phenotype of high-risk myelodysplastic syndromes and acute leukemia cells

Stathmin 1 is an important cytoplasmic microtubule-destabilizing protein that plays critical roles in proliferation and accurate chromosome segregation through regulation of microtubule dynamics. High levels of Stathmin 1 expression have been reported in leukemia and solid tumors. However, Stathmin 1 has not been studied in myelodysplastic syndrome cells. We, herein, report that significantly higher Stathmin 1 levels were observed in proliferating hematopoietic cells, in high-risk MDS and acute leukemia cells. In addition, Stathmin 1 silencing in U937 and Namalwa leukemia cells reduced cell proliferation and clonogenicity. Our data suggest that Stathmin 1 expression may be related to the highly proliferative phenotype of hematopoietic cells and add new insights into the participation of Stathmin 1 in hematological malignancies.