Effect of the G375C and G346E Achondroplasia Mutations on FGFR3 Activation

Two mutations in FGFR3, G380R and G375C are known to cause achondroplasia, the most common form of human dwarfism. The G380R mutation accounts for 98% of the achondroplasia cases, and thus has been studied extensively. Here we study the effect of the G375C mutation on the phosphorylation and the cross-linking propensity of full-length FGFR3 in HEK 293 cells, and we compare the results to previously published results for the G380R mutant. We observe identical behavior of the two achondroplasia mutants in these experiments, a finding which supports a direct link between the severity of dwarfism phenotypes and the level and mechanism of FGFR3 over-activation. The mutations do not increase the cross-linking propensity of FGFR3, contrary to previous expectations that the achondroplasia mutations stabilize the FGFR3 dimers. Instead, the phosphorylation efficiency within un-liganded FGFR3 dimers is increased, and this increase is likely the underlying cause for pathogenesis in achondroplasia. We further investigate the G346E mutation, which has been reported to cause achondroplasia in one case. We find that this mutation does not increase FGFR3 phosphorylation and decreases FGFR3 cross-linking propensity, a finding which raises questions whether this mutation is indeed a genetic cause for human dwarfism

Hepatocyte Growth Factor Increases Osteopontin Expression in Human Osteoblasts through PI3K, Akt, c-Src, and AP-1 Signaling Pathway

BACKGROUND: Hepatocyte growth factor (HGF) has been demonstrated to stimulate osteoblast proliferation and participated bone remodeling. Osteopontin (OPN) is a secreted phosphoglycoprotein that belongs to the SIBLING family and is present during bone mineralization. However, the effects of HGF on OPN expression in human osteoblasts are large unknown. METHODOLOGY/PRINCIPAL FINDINGS: Here we found that HGF induced OPN expression in human osteoblasts dose-dependently. HGF-mediated OPN production was attenuated by c-Met inhibitor and siRNA. Pretreatment of osteoblasts with PI3K inhibitor (Ly294002), Akt inhibitor, c-Src inhibitor (PP2), or AP-1 inhibitor (curcumin) blocked the potentiating action of HGF. Stimulation of osteoblasts with HGF enhanced PI3K, Akt, and c-Src activation. In addition, incubation of cells with HGF also increased c-Jun phosphorylation, AP-1-luciferase activity, and c-Jun binding to the AP-1 element on the OPN promoter. HGF-mediated AP-1-luciferase activity and c-Jun binding to the AP-1 element was reduced by c-Met inhibitor, Ly294002, Akt inhibitor, and PP2. CONCLUSIONS/SIGNIFICANCE: Our results suggest that the interaction between HGF and c-Met increases OPN expression in human osteoblasts via the PI3K, Akt, c-Src, c-Jun, and AP-1 signaling pathway

The impact of polyphenols on chondrocyte growth and survival: a preliminary report

Background: Imbalances in the functional binding of fibroblast growth factors (FGFs) to their receptors (FGFRs) have consequences for cell proliferation and differentiation that in chondrocytes may lead to degraded cartilage. The toxic, proinflammatory, and oxidative response of cytokines and FGFs can be mitigated by dietary polyphenols. Objective: We explored the possible effects of polyphenols in the management of osteoarticular diseases using a model based on the transduction of a mutated human FGFR3 (G380R) in murine chondrocytes. This mutation is present in most cases of skeletal dysplasia and is responsible for the overexpression of FGFR3 that, in the presence of its ligand, FGF9, results in toxic effects leading to altered cellular growth. Design: Different combinations of dietary polyphenols derived from plant extracts were assayed in FGFR3 (G380R) mutated murine chondrocytes, exploring cell survival, chloride efflux, extracellular matrix (ECM) generation, and grade of activation of mitogen-activated protein kinases. Results: Bioactive compounds from Hibiscus sabdariffa reversed the toxic effects of FGF9 and restored normal growth, suggesting a probable translation to clinical requests in humans. Indeed, these compounds activated the intracellular chloride efflux, increased ECM generation, and stimulated cell proliferation. The inhibition of mitogen-activated protein kinase phosphorylation was interpreted as the main mechanism governing these beneficial effects. Conclusions: These findings support the rationale behind the encouragement of the development of drugs that repress the overexpression of FGFRs and suggest the dietary incorporation of supplementary nutrients in the management of degraded cartilage.The authors are grateful for the constant support provided by the Hospital Universitari de Sant Joan and the Universitat Rovira i Virgili. Salvador Fernández-Arroyo is the recipient of a Sara Borrell grant (CD12/00672) from the Instituto de Salud Carlos III, Madrid, Spain. The authors also thank the Andalusian Regional Government Council of Innovation and Science for the Excellence Project P11-CTS-7625 and Generalitat Valenciana for the project PROMETEO/2012/007. This work was also supported by projects of the Fundación Areces and the Fundación MAGAR

Biology of urothelial tumorigenesis: insights from genetically engineered mice

Urothelium, one of the slowest cycling epithelia in the body, embodies a unique biological context for cellular transformation. Introduction of oncogenes into or removing tumor suppressor genes from the urothelial cells or a combination of both using the transgenic and/or knockout mouse approaches has provided useful insights into the molecular mechanisms of urothelial transformation and tumorigenesis. It is becoming increasingly clear that over-activation of the receptor tyrosine kinase (RTK) pathway, as exemplified by the constitutively activated Ha-ras oncogene, is both necessary and sufficient to initiate the low-grade, non-invasive urothelial carcinomas. Dosage of the mutated Ha-ras, but not concurrent inactivation of pro-senescence molecules p16Ink4a and p19Arf, dictates whether and when the low-grade urothelial carcinomas arise. Inactivation of both p53 and pRb, a prevailing paradigm previously proposed for muscle-invasive urothelial tumorigenesis, is found to be necessary but insufficient to initiate this urothelial carcinoma variant. Instead, downregulation in p53/pRb co-deficient urothelial cells of p107, a pRb family member, is associated with the genesis of the muscle-invasive bladder cancers. p53 deficiency also seems to be capable of cooperating with that of PTEN in eliciting invasive urothelial carcinomas. The genetically engineered mice have improved the molecular definition of the divergent pathways of urothelial tumorigenesis and progression, helped delineate the intricate crosstalk among different genetic alterations within a urothelium-specific context, identified new prognostic markers and novel therapeutic targets potentially applicable for clinical intervention, and provided in vivo platforms for testing preventive strategies of bladder cancer

The primary cilium as a dual sensor of mechanochemical signals in chondrocytes

The primary cilium is an immotile, solitary, and microtubule-based structure that projects from cell surfaces into the extracellular environment. The primary cilium functions as a dual sensor, as mechanosensors and chemosensors. The primary cilia coordinate several essential cell signaling pathways that are mainly involved in cell division and differentiation. A primary cilium malfunction can result in several human diseases. Mechanical loading is sense by mechanosensitive cells in nearly all tissues and organs. With this sensation, the mechanical signal is further transduced into biochemical signals involving pathways such as Akt, PKA, FAK, ERK, and MAPK. In this review, we focus on the fundamental functional and structural features of primary cilia in chondrocytes and chondrogenic cells

Consequences of replacing EGFR juxtamembrane domain with an unstructured sequence.

PMC3497011EGFR is the best studied receptor tyrosine kinase. Yet, a comprehensive mechanistic understanding of EGFR signaling is lacking, despite very active research in the field. In this paper, we investigate the role of the juxtamembrane (JM) domain in EGFR signaling by replacing it with a (GGS)(10) unstructured sequence. We probe the effect of this replacement on (i) EGFR phosphorylation, (ii) EGFR dimerization and (iii) ligand (EGF) binding. We show that the replacement of EGFR JM domain with a (GGS)(10) unstructured linker completely abolishes the phosphorylation of all tyrosine residues, without measurable effects on receptor dimerization or ligand binding. Our results suggest that the JM domain does not stabilize the inactive EGFR dimer in the absence of ligand, and is likely critical only for the last step of EGFR activation, the ligand-induced transition from the inactive to active dimer.JH Libraries Open Access Fun

Effective corporate social responsibility as a panacea for peaceful cohabitation between organisations and host communities: University of agriculture Makurdi Nigeria's experience between 1988-2015

Corporate Social responsibility is the ability of organisations to give back to the society through mutually beneficial initiatives to guarantee a conflict-free co-existence. Consequently, this study was carried out to assess the impact of corporate social responsibility of the Federal University of Agriculture, Makurdi on its host communities. Snowball sampling technique was used to select 100 respondents for the study. Data were analyzed using frequencies, percentages and paired sample t-test methods. The results revealed that employment opportunities, agricultural innovations, extension services (adopted villages), electricity and water were the specific social responsibilities carried within the host communities. . The result of the Chi square statistic (20.967) at 5 percent level of probability showed that the projects had little positive impact on the means of livelihood of her host communities. It was concluded that the Cooperate Social Responsibility (CSR) projects of FUAM in the host communities were inadequate, hence the occasional disturbance by youths. It was recommended that the university should embark on more CSR Projects in the host communities

Adaptive statistical iterative reconstruction reduces patient radiation dose in neuroradiology CT studies.

INTRODUCTION: Adaptive statistical iterative reconstruction (ASIR) can decrease image noise, thereby generating CT images of comparable diagnostic quality with less radiation. The purpose of this study is to quantify the effect of systematic use of ASIR versus filtered back projection (FBP) for neuroradiology CT protocols on patients' radiation dose and image quality. METHODS: We evaluated the effect of ASIR on six types of neuroradiologic CT studies: adult and pediatric unenhanced head CT, adult cervical spine CT, adult cervical and intracranial CT angiography, adult soft tissue neck CT with contrast, and adult lumbar spine CT. For each type of CT study, two groups of 100 consecutive studies were retrospectively reviewed: 100 studies performed with FBP and 100 studies performed with ASIR/FBP blending factor of 40 %/60 % with appropriate noise indices. The weighted volume CT dose index (CTDIvol), dose-length product (DLP) and noise were recorded. Each study was also reviewed for image quality by two reviewers. Continuous and categorical variables were compared by t test and free permutation test, respectively. RESULTS: For adult unenhanced brain CT, CT cervical myelography, cervical and intracranial CT angiography and lumbar spine CT both CTDIvol and DLP were lowered by up to 10.9 % (p < 0.001), 17.9 % (p = 0.005), 20.9 % (p < 0.001), and 21.7 % (p = 0.001), respectively, by using ASIR compared with FBP alone. Image quality and noise were similar for both FBP and ASIR. CONCLUSION: We recommend routine use of iterative reconstruction for neuroradiology CT examinations because this approach affords a significant dose reduction while preserving image quality