FGFR2-Cbl interaction in lipid rafts triggers attenuation of PI3K/Akt signaling and osteoblast survival

Fibroblast growth factor receptor (FGFR) signaling plays an important role in skeletogenesis. The molecular mechanisms triggered by activated FGFR in bone forming cells are however not fully understood. In this study, we identify a role for phosphatidylinositol 3-kinase (PI3K) signaling in cell apoptosis induced by FGFR2 activation in osteoblasts. We show that FGFR2 activation leads to decrease PI3K protein levels, resulting in attenuation of PI3K signaling in human osteoblasts. Biochemical and molecular analyses revealed that the attenuated PI3K signaling induced by FGFR2 activation is due to increased Cbl-PI3K molecular interaction mediated by the Cbl Y731 residue, which results in increased PI3K ubiquitination and proteasome degradation. Biochemical and immunocytochemical analyses showed that FGFR2 and Cbl interact in raft micro-domains at the plasma membrane. FGFR2 activation increases FGFR2 and Cbl recruitment in micro-domains, resulting in increased molecular interactions. Consistently, functional analyses showed that the attenuation of PI3K/Akt signaling triggered by FGFR2 activation results in increased osteoblast apoptosis. These results identify a functional molecular mechanism by which activated FGFR2 recruits Cbl in raft micro-domains to trigger PI3K ubiquitination and proteasome degradation, and reveal a novel role for PI3K/Akt attenuation in the control of osteoblast survival by FGFR2 signaling.     

Sciatica from disk herniation: Medical treatment or surgery?

Disk-related sciatica is a common disorder that resolves without surgery in 95% of patients within 1 to 12months. Several treatment strategies designed to hasten recovery, enable a return to previous social and occupational activities, and prevent chronicization have been evaluated. Available efficacy data support the use of analgesics, nonsteroidal anti-inflammatory drugs, and epidural steroid injections, which probably relieve the pain and improve the quality of life without radically changing the midterm outcome. After a specialized evaluation of physical, psychological, social, and occupational factors, surgery may be offered to patients with persistent nerve root pain (as opposed to low back pain). The complication rate ranges from 1% to 3%. Surgery is clearly effective, shortening the time to recovery by about 50% compared to nonsurgical treatment. Whether one specific surgical procedure is better than others remains unclear. Methodological weaknesses of studies evaluating the efficacy of percutaneous methods preclude definitive conclusions. Bed rest, systemic glucocorticoid therapy, spinal manipulation, bracing, spinal traction, and physical therapy have no proven effects on the outcome of sciatica.     

Comparison of 2 systems for identifying nonfermenting or fermenting oxidase-positive gram-negative bacilli

The N/F FLOW and API 20 NE identification systems were compared for their ability to identify 182 strains of either non-fermentative or fermentative oxidase-positive gram-negative bacilli. Agreement with the identification given by conventional methods was achieved for 91,7 per cent of strains by the API System but for only 81,9 per cent of strains by the N/F System. Complementary tests were needed to identify 35,4 per cent of strains using the API System but 65,2 per cent using the N/F System.     

Idazoxan and 8-OH-DPAT modify the behavioral effects induced by either NA, or 5-HT, or dual NA/5-HT reuptake inhibition in the rat forced swimming test.

The rat forced swimming test (FST) predicts the efficacy of antidepressants, which decrease immobility duration in the test, and can distinguish selective serotonin (5-HT) and noradrenaline (NA) reuptake inhibitors, which, respectively, increase swimming and climbing behaviors. However, dual 5-HT and NA reuptake-inhibition produces climbing behavior solely, thereby suggesting with other data that the NA-system mediates inhibiting interactions on 5-HT-induced swimming in the FST. Since alpha(2)-adrenoreceptors and 5-HT(1A)-receptors have important regulatory functions and are involved in 5-HT/NA interactions, we examined whether the alpha(2)-receptor-antagonist idazoxan and the 5-HT(1A)-receptor-agonist 8-hydroxy-2-(di-n-propylamino)-tetralin (8-OH-DPAT) would modify the behavioral pattern induced in the FST by either selective or non-selective antidepressant treatments. The rats were treated subacutely (3 injections IP over 48 h) with: (a) idazoxan (0.5-10 mg/kg) alone, and in combination with desipramine (10 mg/kg), or desipramine + fluoxetine (10/10 mg/kg), or the dual serotonin/noradrenaline reuptake-inhibitor milnacipran (20 mg/kg). (b) 8-OH-DPAT (0.25-1 mg/kg) alone, and in combination with either desipramine (10 mg/kg) or fluoxetine (10 mg/kg). The results indicated: (a) Idazoxan (0.5, 5, 10 mg/kg) produced no anti-immobility effects per se in the FST, antagonized the effects of the NA-reuptake-inhibitor desipramine, and allowed desipramine + fluoxetine, as well as milnacipran, to increase swimming behavior. (b) 8-OH-DPAT produced non-significant effects per se, potentiated desipramine-induced antidepressant-like effects on immobility and climbing, and both antagonized swimming and produced climbing behavior in combination with fluoxetine. Our data support clinical trials suggesting that alpha(2)-receptor-antagonists and 5-HT(1A)-receptor-agonists may be of interest in augmentation strategies for antidepressant treatments. The scoring of active behaviors in the FST appears to be an interesting tool for studying 5-HT/NA interactions induced by antidepressants, as well as for the testing of augmentation strategies.     

Characterisation of cellular changes which influence progression of human papillomavirus type-16 immortalised keratinocytes to anchorage-independent phenotype

Cellular alterations which influence progression to an anchorage-independent phenotype are poorly understood. Few immortalised keratinocyte lines have been reported to form colonies in semi-solid medium, and the important role of the anchorage-dependence in controlling the behaviour of keratinocytes reflects the resistance of these cells to form colonies in soft agar. We describe here a model for studying in vitro the progression of human papillomavirus type-16 (HPV-16) immortalised keratinocytes from the early stages of immortalisation to an anchorage-independent phenotype. By an extensive selection procedure we have isolated three related cell lines, one immortalised, one weakly anchorage independent and one completely anchorage-independent. The comparison of these three lines gave a clear indication that this in vitro altered growth property is mainly correlated with a deregulation of the epidermal growth factor receptor (ECFR), leading to an increased proliferation rate of the cells coupled with changes in keratin expression.     

Functional consequences of integrin gene mutations in mice

Integrins are cell-surface receptors responsible for cell attachment to extracellular matrices and to other cells. The application of mouse genetics has significantly increased our understanding of integrin function in vivo. In this review, we summarize the phenotypes of mice carrying mutant integrin genes and compare them with phenotypes of mice lacking the integrin ligands.