RESUMEN
Directed cell migrations are important for development, but the signaling pathways and mechanisms responsible for guiding cell migration in vivo are poorly understood. Migration of border cells during Drosophila oogenesis is a simple and attractive model system in which to address these questions. We demonstrate that PVR, a receptor tyrosine kinase related to mammalian PDGF and VEGF receptors, acts in border cells to guide them to the oocyte. The oocyte is the source of a ligand for PVR, PDGF/VEGF factor 1 (PVF1). Intriguingly, the guidance function of PVR is largely redundant with that of EGFR. We present evidence implicating Rac and the Rac activator Mbc/DOCK180/CED-5 as mediators of the guidance signal.
Asunto(s)
Movimiento Celular/fisiología , Proteínas del Citoesqueleto , Proteínas de Drosophila , Drosophila melanogaster/fisiología , Proteínas del Huevo/metabolismo , Proteínas de Insectos/metabolismo , Oocitos/fisiología , Proteínas Tirosina Quinasas Receptoras/metabolismo , Actinas/metabolismo , Secuencia de Aminoácidos , Animales , Citoesqueleto/metabolismo , Drosophila melanogaster/citología , Proteínas del Huevo/química , Proteínas del Huevo/genética , Receptores ErbB/metabolismo , Femenino , Humanos , Immunoblotting , Proteínas de Insectos/química , Proteínas de Insectos/genética , Ligandos , Microscopía Fluorescente , Datos de Secuencia Molecular , Oocitos/citología , Oogénesis/fisiología , Ovario/metabolismo , Receptores de Factores de Crecimiento/metabolismo , Receptores del Factor de Crecimiento Derivado de Plaquetas/metabolismo , Receptores de Factores de Crecimiento Endotelial Vascular , Alineación de Secuencia , Transducción de Señal/fisiología , Proteínas de Unión al GTP rac/metabolismoAsunto(s)
Transformación Celular Neoplásica/genética , Proteínas Nucleares/genética , Proteínas Tirosina Quinasas/genética , Proteínas Tirosina Quinasas Receptoras/genética , Quinasa de Linfoma Anaplásico , Animales , División Celular , Genes ras , Linfoma Anaplásico de Células Grandes/genética , Proteínas Nucleares/metabolismo , Nucleofosmina , Fragmentos de Péptidos , Ratas , Proteínas Tirosina Quinasas Receptoras/metabolismo , Proteínas Recombinantes de Fusión/genética , Proteínas Recombinantes de Fusión/metabolismo , Proteínas Represoras/genética , Proteínas Represoras/metabolismoRESUMEN
Directed cell migration is important for many aspects of normal animal development, but little is known about how cell migrations are guided or the mechanisms by which guidance cues are translated into directed cell movement. Here we present evidence that signaling mediated by the epidermal growth factor receptor (EGFR) guides dorsal migration of border cells during Drosophila oogenesis. The transforming growth factor-alpha (TGF-alpha)-like ligand Gurken appears to serve as the guidance cue. To mediate this guidance function, EGFR signals via a pathway that is independent of Raf-MAP kinase and receptor-specific.
Asunto(s)
Movimiento Celular , Proteínas de Drosophila , Drosophila melanogaster/citología , Drosophila melanogaster/fisiología , Receptores ErbB/fisiología , Neurregulinas , Transducción de Señal , Factor de Crecimiento Transformador alfa , Animales , Drosophila melanogaster/genética , Receptores ErbB/genética , Femenino , Proteínas de Insectos/genética , Proteínas de Insectos/fisiología , Ligandos , Sistema de Señalización de MAP Quinasas , Proteínas Quinasas Activadas por Mitógenos/metabolismo , Mutación , Oocitos/citología , Oocitos/fisiología , Oogénesis , Folículo Ovárico/citología , Folículo Ovárico/fisiología , Proteínas Proto-Oncogénicas c-raf/metabolismo , Factores de Crecimiento Transformadores/genética , Factores de Crecimiento Transformadores/fisiologíaRESUMEN
We have cloned from a chicken intestinal cDNA library Cmdr1, the first avian P-glycoprotein. Cmdr1 is 67% and 69% identical to proteins encoded by the human MDR1 and MDR2 genes, respectively. Functional expression of Cmdr1 in both mouse NIH 3T3 and yeast cells demonstrated that Cmdr1 represents the avian ortholog of human Mdr1, since it confers resistance to several anticancer drugs and the fluorescent dye rhodamine 6G. Northern and immunoblot analysis showed that CMDR1 is highly expressed throughout the intestine and in the liver, and to a considerable extent in kidney, brain, lung, heart, eye and follicles. In situ hybridization revealed a cell type-specific expression of CMDR1 in the intestinal epithelium, with high levels in the villi of the small and large intestine as well as crypt cells. These data suggest that Cmdr1 could play a role in intestinal detoxification. Most interestingly, immunoblotting showed that Cmdr1 is also expressed in ovarian tissues, particularly in theca cells, the major site for ovarian estrogen production in birds. Indeed, competition experiments indicated that Cmdr1 interacts with estradiol, since rhodamine 6G efflux was efficiently blocked by estradiol in NIH 3T3 cells expressing Cmdr1. Rhodamine efflux was also blocked by PSC-833, a specific inhibitor of steroid-transporting P-glycoproteins from mammalian cells. We propose that Cmdr1 in ovarian cells could be involved in the cell type-specific transport or release of estrogen that is essential for avian follicular development.