ABSTRACT
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.
Subject(s)
Cell Movement/physiology , Cytoskeletal Proteins , Drosophila Proteins , Drosophila melanogaster/physiology , Egg Proteins/metabolism , Insect Proteins/metabolism , Oocytes/physiology , Receptor Protein-Tyrosine Kinases/metabolism , Actins/metabolism , Amino Acid Sequence , Animals , Cytoskeleton/metabolism , Drosophila melanogaster/cytology , Egg Proteins/chemistry , Egg Proteins/genetics , ErbB Receptors/metabolism , Female , Humans , Immunoblotting , Insect Proteins/chemistry , Insect Proteins/genetics , Ligands , Microscopy, Fluorescence , Molecular Sequence Data , Oocytes/cytology , Oogenesis/physiology , Ovary/metabolism , Receptors, Growth Factor/metabolism , Receptors, Platelet-Derived Growth Factor/metabolism , Receptors, Vascular Endothelial Growth Factor , Sequence Alignment , Signal Transduction/physiology , rac GTP-Binding Proteins/metabolismSubject(s)
Cell Transformation, Neoplastic/genetics , Nuclear Proteins/genetics , Protein-Tyrosine Kinases/genetics , Receptor Protein-Tyrosine Kinases/genetics , Anaplastic Lymphoma Kinase , Animals , Cell Division , Genes, ras , Lymphoma, Large-Cell, Anaplastic/genetics , Nuclear Proteins/metabolism , Nucleophosmin , Peptide Fragments , Rats , Receptor Protein-Tyrosine Kinases/metabolism , Recombinant Fusion Proteins/genetics , Recombinant Fusion Proteins/metabolism , Repressor Proteins/genetics , Repressor Proteins/metabolismABSTRACT
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.
Subject(s)
Cell Movement , Drosophila Proteins , Drosophila melanogaster/cytology , Drosophila melanogaster/physiology , ErbB Receptors/physiology , Neuregulins , Signal Transduction , Transforming Growth Factor alpha , Animals , Drosophila melanogaster/genetics , ErbB Receptors/genetics , Female , Insect Proteins/genetics , Insect Proteins/physiology , Ligands , MAP Kinase Signaling System , Mitogen-Activated Protein Kinases/metabolism , Mutation , Oocytes/cytology , Oocytes/physiology , Oogenesis , Ovarian Follicle/cytology , Ovarian Follicle/physiology , Proto-Oncogene Proteins c-raf/metabolism , Transforming Growth Factors/genetics , Transforming Growth Factors/physiologyABSTRACT
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.
