RESUMO
Gene targeting studies have indicated that the two receptors for PDGF, alpha and beta, direct unique functions during development. Distinct ligand affinities, patterns of gene expression, and/or mechanisms of signal relay may account for functional specificity of the two PDGF receptor isoforms. To distinguish between these factors, we have created two complementary lines of knockin mice in which the intracellular signaling domains of one PDGFR have been removed and replaced by those of the other PDGFR. While both lines demonstrated substantial rescue of normal development, substitution of the PDGFbetaR signaling domains with those of the PDGFalphaR resulted in varying degrees of vascular disease. This observation provides a framework for discussing the evolution of receptor tyrosine kinase functional specificity.
Assuntos
Receptor alfa de Fator de Crescimento Derivado de Plaquetas/metabolismo , Receptor beta de Fator de Crescimento Derivado de Plaquetas/metabolismo , Transdução de Sinais , Animais , Células Cultivadas , Deleção de Genes , Marcação de Genes/métodos , Teste de Complementação Genética , Genótipo , Glomerulonefrite/genética , Glomerulonefrite/patologia , Cardiopatias Congênitas/genética , Cardiopatias Congênitas/patologia , Histocitoquímica , Rim/anormalidades , Rim/embriologia , Rim/patologia , Camundongos , Camundongos Transgênicos , Proteínas Quinases Ativadas por Mitógeno/metabolismo , Fosforilação , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , Estrutura Terciária de Proteína , Receptor alfa de Fator de Crescimento Derivado de Plaquetas/genética , Receptor beta de Fator de Crescimento Derivado de Plaquetas/genética , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/metabolismo , Retina/anormalidades , Retina/embriologia , Retina/patologia , Trombose/genética , Trombose/patologia , Fatores de TempoRESUMO
Signal transduction by the platelet-derived growth-factor receptor beta (PDGFR-beta) tyrosine kinase is required for proper formation of vascular smooth muscle cells (VSMC). However, the importance of individual PDGFR-beta signal transduction pathways in vivo is not known. To investigate the role of two of the pathways believed to be critical for PDGF signal transduction, we have generated mice that bear a PDGFR-beta that can no longer activate PI3kinase or PLCgamma. Although these mutant mice have normal vasculature, we provide multiple lines of evidence in vivo and from cells derived from the mutant mice that suggest that the mutant PDGFR-beta operates at suboptimal levels. Our observations indicate that although loss of these pathways can lead to attenuated PDGF-dependent cellular function, certain PDGFR-beta-induced signal cascades are not essential for survival in mice.