RESUMO
Son of Sevenless 1 (SOS1) is a dual guanine nucleotide exchange factor (GEF) that activates the small GTPases RAC and RAS. Although the molecular mechanisms of RAS GEF catalysis have been unveiled, how SOS1 acquires RAC GEF activity and what is the physio-pathological relevance of this activity is much less understood. Here we show that SOS1 is tyrosine phosphorylated on Y1196 by ABL. Phosphorylation of Y1196 controls SOS1 inter-molecular interaction, is required to promote the exchange of nucleotides on RAC in vitro and for platelet-derived growth factor (PDGF) activation of RAC- and RAC-dependent actin remodeling and cell migration. SOS1 is also phosphorylated on Y1196 by BCR-ABL in chronic myelogenous leukemic cells. Importantly, in these cells, SOS1 is required for BCR-ABL-mediated activation of RAC, cell proliferation and transformation in vitro and in a xenograft mouse model. Finally, genetic removal of Sos1 in the bone marrow-derived cells (BMDCs) from Sos1fl/fl mice and infected with BCR-ABL causes a significant delay in the onset of leukemogenesis once BMDCs are injected into recipient, lethally irradiated mice. Thus, SOS1 is required for full transformation and critically contribute to the leukemogenic potential of BCR-ABL.
Assuntos
Transformação Celular Neoplásica/genética , Transformação Celular Neoplásica/metabolismo , Proteínas de Fusão bcr-abl/genética , Fatores de Troca do Nucleotídeo Guanina/metabolismo , Proteína SOS1/metabolismo , Animais , Linhagem Celular Tumoral , Movimento Celular , Proliferação de Células , Modelos Animais de Doenças , Proteínas de Fusão bcr-abl/metabolismo , Humanos , Leucemia/genética , Leucemia/metabolismo , Camundongos , Fosforilação , Fator de Crescimento Derivado de Plaquetas/metabolismo , Proteínas Proto-Oncogênicas p21(ras)/metabolismo , Tirosina/metabolismo , Proteínas rac de Ligação ao GTP , Proteínas rac1 de Ligação ao GTP/metabolismoRESUMO
The dissection of the molecular circuitries at the base of cell life and the identification of their abnormal transformation during carcinogenesis rely on the characterization of biological phenotypes generated by targeted overexpression or deletion of gene products through genetic manipulation. Fluorescence microscopy provides a wide variety of tools to monitor cell life with minimal perturbations. The observation of living cells requires the selection of a correct balance between temporal, spatial and "statistical" resolution according to the process to be analyzed. In the following paper ad hoc developed optical tools for dynamical tracking from cellular to molecular resolution will be presented. Particular emphasis will be devoted to discuss how to exploit light-matter interaction to selectively target specific molecular species, understanding the relationships between their intracellular compartmentalization and function.