Suppression of the PI3K subunit p85α delays embryoid body development and inhibits cell adhesion

Characterization of lncRNA and mRNA profiles in ciliary body in experimental myopia

Currently, researchers have mainly focused on the role of the tissues of the posterior segment of the eyes in the development of myopia. However, the ciliary body, an anterior ocular tissue that contracts to initiate the process of accommodation, may also play an important role in the progression of myopia due to the increased demand for near work. In the present study, we established a lens-induced myopia (LIM) animal model in guinea pigs and investigated the molecular changes in the ciliary body associated with the development of myopia based on RNA sequencing. As a result, 871 differentially expressed (DE) mRNAs and 19 DE lncRNAs were identified in the ciliary body between the LIM group and the normal control group. In addition, the lncRNA-mRNA co-expression analysis was performed to explore the target genes of lncRNAs, which were mainly enriched in the Rap1 signaling pathway, cytokine-cytokine receptor interaction, and complement and coagulation cascades pathways based on the functional enrichment analysis. Among the target genes of lncRNAs, three hub genes, including Ctnnb1, Pik3r1, and Itgb1, were found to be involved in the Rap1 signaling pathway. Interestingly, two crucial genes, Grk1 and Pde6a, which are mainly expressed in retinal photoreceptors, were enriched in visual perception in the ciliary body in functional analysis and were verified to be expressed in the ciliary body. These findings indicate the molecular pathogenetic role of the ciliary body in myopia and provide new insights into the underlying mechanism of myopia development. Further studies are needed to explore the specific contributions of these identified lncRNAs and mRNAs to the development of myopia.

Inhibition of cell migration by focal adhesion kinase: Time-dependent difference in integrin-induced signaling between endothelial and hepatoblastoma cells

Angiogenesis plays an important role in the development and progression of tumors, and it involves a series of signaling pathways contributing to the migration of endothelial cells for vascularization and to the invasion of cancer cells for secondary tumor formation. Among these pathways, the focal adhesion kinase (FAK) signaling cascade has been implicated in a variety of human cancers in connection with cell adhesion and migration events leading to tumor angiogenesis, metastasis and invasion. Therefore, the inhibition of FAK in endothelial and/or cancer cells is a potential target for anti-angiogenic therapy. In the present study, a small-molecule FAK inhibitor, 1,2,4,5-benzenetetramine tetrahydrochloride (Y15), was used to study the effects of FAK inhibition on the adhesion and migration behaviors of vascular endothelial cells (VECs) and human hepatoblastoma cells. Furthermore, the time-dependent differences in proteins associated with the integrin-mediated FAK/Rho GTPases signaling pathway within 2 h were examined. The results indicated that the inhibition of FAK significantly decreased the migration ability of VECs and human hepatoblastoma cells in a dose-dependent manner. Inhibition of FAK promoted cell detachment by decreasing the expression of focal adhesion components, and blocked cell motility by reducing the level of Rho GTPases. However, the expression of crucial proteins involved in integrin-induced signaling in two cell lines exhibited a time-dependent difference with increased duration of FAK inhibitor treatment, suggesting different mechanisms of FAK-mediated cell migration behavior. These results suggest that the mechanism underlying FAK-mediated adhesion and migration behavior differs among various cells, which is expected to provide evidence for future FAK therapy targeted against tumor angiogenesis.

P42 Ebp1 regulates the proteasomal degradation of the p85 regulatory subunit of PI3K by recruiting a chaperone-E3 ligase complex HSP70/CHIP

The short isoform of ErbB3-binding protein 1 (Ebp1), p42, is considered to be a potent tumor suppressor in a number of human cancers, although the mechanism by which it exerts this tumor-suppressive activity is unclear. Here, we report that p42 interacts with the cSH2 domain of the p85 subunit of phosphathidyl inositol 3-kinase (PI3K), leading to inhibition of its lipid kinase activity. Importantly, we found that p42 induces protein degradation of the p85 subunit and further identified HSP70/CHIP complex as a novel E3 ligase for p85 that is responsible for p85 ubiquitination and degradation. In this process, p42 couples p85 to the HSP70/CHIP-mediated ubiquitin–proteasomal system (UPS), thereby promoting a reduction of p85 levels both in vitro and in vivo. Thus, the tumor-suppressing effects of p42 in cancer cells are driven by negative regulation of the p85 subunit of PI3K.

Cycling around cell-cell adhesion with Rho GTPase regulators

The formation and stability of epithelial adhesive systems, such as adherens junctions, desmosomes and tight junctions, rely on a number of cellular processes that ensure a dynamic interaction with the cortical cytoskeleton, and appropriate delivery and turnover of receptors at the surface. Unique signalling pathways must be coordinated to allow the coexistence of distinct adhesive systems at discrete sub-domains along junctions and the specific properties they confer to epithelial cells. Rho, Rac and Cdc42 are members of the Rho small GTPase family, and are well-known regulators of cell-cell adhesion. The spatio-temporal control of small GTPase activation drives specific intracellular processes to enable the hierarchical assembly, morphology and maturation of cell-cell contacts. Here, we discuss the small GTPase regulators that control the precise amplitude and duration of the levels of active Rho at cell-cell contacts, and the mechanisms that tailor the output of Rho signalling to a particular cellular event. Interestingly, the functional interaction is reciprocal; Rho regulators drive the maturation of cell-cell contacts, whereas junctions can also modulate the localisation and activity of Rho regulators to operate in diverse processes in the epithelial differentiation programme.

miR-200c and GATA binding protein 4 regulate human embryonic stem cell renewal and differentiation

Human embryonic stem cells (hESCs) are functionally unique for their self-renewal ability and pluripotency, but the molecular mechanisms giving rise to these properties are not fully understood. hESCs can differentiate into embryoid bodies (EBs) containing ectoderm, mesoderm, and endoderm. In the miR-200 family, miR-200c was especially enriched in undifferentiated hESCs and significantly downregulated in EBs. The knockdown of the miR-200c in hESCs downregulated Nanog expression, upregulated GATA binding protein 4 (GATA4) expression, and induced hESC apoptosis. The knockdown of GATA4 rescued hESC apoptosis induced by downregulation of miR-200c. miR-200c directly targeted the 3'-untranslated region of GATA4. Interestingly, the downregulation of GATA4 significantly inhibited EB formation in hESCs. Overexpression of miR-200c inhibited EB formation and repressed the expression of ectoderm, endoderm, and mesoderm markers, which could partially be rescued by ectopic expression of GATA4. Fibroblast growth factor (FGF) and activin A/nodal can sustain hESC renewal in the absence of feeder layer. Inhibition of transforming growth factor-β (TGF-β[Symbol: see text])/activin A/nodal signaling by SB431542 treatment downregulated the expression of miR-200c. Overexpression of miR-200c partially rescued the expression of Nanog/phospho-Smad2 that was downregulated by SB431542 treatment. Our observations have uncovered novel functions of miR-200c and GATA4 in regulating hESC renewal and differentiation.

miR-376a suppresses proliferation and induces apoptosis in hepatocellular carcinoma

MicroRNAs are known to be involved in the pathogenesis of hepatocellular carcinoma (HCC). This study aims to explore the potential biological function of miR-376a, which was found to be inhibited after partial hepatectomy, in HCC. We discovered that miR-376a was frequently down-regulated in HCC cell lines and HCC tissues, while higher relative level of miR-376a was significantly associated with high serum AFP level. Over-expression of miR-376a not only inhibited proliferation but induced apoptosis in Huh7 cells. Additionally, p85α (PIK3R1) was identified as a direct and functional target of miR-376a in Huh7 cells. Moreover, we confirmed that p85α and miR-376a were inversely correlated in HCC. These findings suggest that down-regulation of miR-376a may contribute to the development of HCC by targeting p85α.