Schizophrenia susceptibility gene product dysbindin-1 regulates the homeostasis of cyclin D1

Expression analysis of type I ARF small GTPases ARF1-3 during mouse brain development

BACKGROUND

ARF (ADP-ribosylation factor) GTPases are major regulators of intracellular trafficking, and classified into 3 groups (Type I - III), among which the type I group members, ARF1 and 3, are responsible genes for neurodevelopmental disorders.

METHODS

In this study, we analysed the expression of Type I ARFs ARF1-3 during mouse brain development using biochemical and morphological methods.

RESULTS

Western blotting analyses revealed that ARF1-3 are weakly expressed in the mouse brain at embryonic day 13 and gradually increase until postnatal day 30. ARF1-3 appear to be abundantly expressed in various telencephalon regions. Biochemical fractionation studies detected ARF1-3 in the synaptosome fraction of cortical neurons containing both pre- and post-synapses, however ARF1-3 were not observed in post-synaptic compartments. In immunohistochemical analyses, ARF1-3 appeared to be distributed in the cytoplasm and dendrites of cortical and hippocampal neurons as well as in the cerebellar molecular layer including dendrites of Purkinje cells and granule cell axons. Immunofluorescence in primary cultured hippocampal neurons revealed that ARF1-3 are diffusely distributed in the cytoplasm and dendrites with partial colocalization with a pre-synaptic marker, synaptophysin.

CONCLUSIONS

Overall, our results support the notion that ARF1-3 could participate in vesicle trafficking both in the dendritic shaft (excluding spines) and axon terminals (pre-synaptic compartments).

Objective to identify and verify the regulatory mechanism of DTNBP1 as a prognostic marker for hepatocellular carcinoma

Although the overall survival of hepatocellular carcinoma (HCC) patients has been significantly improved, prognostic clinical evaluation remains a substantial problem owing to the heterogeneity and complexity of tumor. A reliable and accurate predictive biomarker may assist physicians in better monitoring of patient treatment outcomes and follow the overall survival of patients. Accumulating evidence has revealed that DTNBP1 plays functional roles in cancer prognosis. Therefore, the expression and function of DTNBP1in HCC was systematically investigated in our study. The expression and prognostic value of DTNBP1 were investigated using the data from Cancer Genome Atlas (TCGA) database, Gene Expression Omnibus (GEO) cohorts and clinical samples. A series of cellular function assays were performed to elucidate the effect of DTNBP1 on cellular proliferation, apoptosis and metastasis. Kyoto Encyclopaedia of Genes and Genomes (KEGG) pathway enrichment and Protein–protein interaction (PPI) network construction were performed to screen the genes with highest interaction scores with DTNBP1. Finally, the underlying mechanism was also analyzed using Gene Set Enrichment Analysis (GSEA) and confirmed using RT-qPCR and western blotting. DTNBP1 was upregulated in many types of cancers, especially in HCC. The DTNBP1 expression levels is associated with clinicopathologic variables and patient survival status. The differential expression of DTNBP1 could be used to determine the risk stratification of patients with HCC. DTNBP1 deficiency inhibited cell proliferation and metastasis, but promoted cell apoptosis. Mechanistically, DTNBP1 regulated the cell cycle progression through affecting the expression of cell cycle-related genes such as CDC25A, CCNE1, CDK2, CDC20, CDC25B, CCNB1, and CDK1. DTNBP1, which regulates the cell cycle progression, may be used as a prognostic marker for HCC.

The synaptic scaffolding protein CNKSR2 interacts with CYTH2 to mediate hippocampal granule cell development

CNKSR2 is a synaptic scaffolding molecule that is encoded by the CNKSR2 gene located on the X chromosome. Heterozygous mutations to CNKSR2 in humans are associated with intellectual disability and epileptic seizures, yet the cellular and molecular roles for CNKSR2 in nervous system development and disease remain poorly characterized. Here, we identify a molecular complex comprising CNKSR2 and the guanine nucleotide exchange factor (GEF) for ARF small GTPases, CYTH2, that is necessary for the proper development of granule neurons in the mouse hippocampus. Notably, we show that CYTH2 binding prevents proteasomal degradation of CNKSR2. Furthermore, to explore the functional significance of coexpression of CNKSR2 and CYTH2 in the soma of granule cells within the hippocampal dentate gyrus, we transduced mouse granule cell precursors in vivo with small hairpin RNAs (shRNAs) to silence CNKSR2 or CYTH2 expression. We found that such manipulations resulted in the abnormal localization of transduced cells at the boundary between the granule cell layer and the hilus. In both cases, CNKSR2-knockdown and CYTH2-knockdown cells exhibited characteristics of immature granule cells, consistent with their putative roles in neuron differentiation. Taken together, our results demonstrate that CNKSR2 and its molecular interaction partner CYTH2 are necessary for the proper development of dentate granule cells within the hippocampus through a mechanism that involves the stabilization of a complex comprising these proteins.

Dysbindin promotes progression of pancreatic ductal adenocarcinoma via direct activation of PI3K

Pancreatic ductal adenocarcinoma (PDAC) represents a biggest challenge in clinic oncology due to its invasiveness and lack of targeted therapeutics. Our recent study showed that schizophrenia susceptibility factor dysbindin exhibited significant higher level in serum of PDAC patients. However, the functional relevance of dysbindin in PDAC is still unclear. Here, we show that dysbindin promotes tumor growth both in vitro and in vivo by accelerating the G1/S phase transition in cell cycle via PI3K/AKT signaling pathway. Mechanistically, dysbindin interacts with PI3K and stimulates the kinase activity of PI3K. Moreover, overexpression of dysbindin in PDAC is correlated with clinicopathological characteristics significantly, such as histological differentiation (P = 0.011) and tumor size (P = 0.007). Kaplan-Meier survival curves show that patients with high dysbindin expression exhibit poorer overall survival, compared to those with low dysbindin expression (P < 0.001). Multivariate analysis reveals that dysbindin is an independent prognostic factor for pancreatic ductal adenocarcinoma (P = 0.001). Thus, our findings reveal that dysbindin is a novel PI3K activator and promotes PDAC progression via stimulation of PI3K/AKT. Dysbindin therefore represents a potential target for prognosis and therapy of PDAC.