RESUMO
Four transmembrane tyrosine kinases constitute the ErbB protein family: epidermal growth factor receptor (EGFR) or ErbB1, ErbB2, ErbB3, and ErbB4. In general, the structure and mechanism of the activation of these members are similar. However, significant differences in homologous desensitization are known between EGFR and ErbB4. Desensitization of ligand-occupied EGFR occurs by endocytosis, while that of ErbB4 occurs by selective cleavage at the cell surface. Because ErbB4 is abundantly expressed in neurons from fetal to adult brains, elucidation of the desensitization mechanism is important to understand neuronal development and synaptic functions. Recently, it has become clear that heterologous desensitization of EGFR and ErbB4 are induced by endocytosis and cleavage, respectively, similar to homologous desensitization. It has been reported that heterologous desensitization of EGFR is induced by serine phosphorylation of EGFR via the p38 mitogen-activated protein kinase (p38 MAP kinase) pathway in various cell lines, including alveolar epithelial cells. In contrast, the protein kinase C pathway is involved in ErbB4 cleavage. In this review, we will describe recent advances in the desensitization mechanisms of EGFR and ErbB4, mainly in alveolar epithelial cells and hypothalamic neurons, respectively.
Assuntos
Receptores ErbB/metabolismo , Animais , Linhagem Celular , Células Epiteliais/metabolismo , Receptores ErbB/genética , Flagelina/farmacologia , Hormônio Liberador de Gonadotropina/farmacologia , Hormônio Liberador de Gonadotropina/fisiologia , Humanos , Hipotálamo/citologia , Hipotálamo/metabolismo , Sistema de Sinalização das MAP Quinases/fisiologia , Neurônios/metabolismo , Fosforilação , Proteína Quinase C/fisiologia , Alvéolos Pulmonares/citologia , Alvéolos Pulmonares/metabolismo , Receptor ErbB-4 , Serina/metabolismo , Transdução de Sinais/fisiologia , Ativação Transcricional , Fator de Necrose Tumoral alfa/fisiologiaRESUMO
We studied retrospectively amount of bleeding, clamping time, and the presence or absence of ischemia-reperfusion injury in all seven cases of IABO performed for placenta accreta from 2007 to 2012 at our hospital. We also examined rSO2 change before and after clamping in four cases in which lower-limb rSO2 monitoring was performed with NIRS (near-infrared spectroscopy). There was no case suspected of ischemia-reperfusion injury during and after clamping with the amount of bleeding around 1,580-10,973 ml (mean 4,536 ml) and clamping time of 10-83 min (mean 44 min). No significant decrease was observed in lower-limb rSO2 with 73.5 ± 5.9% before clamping and 70.8 ± 5.6% (mean ± SD) after clamping.