Apical accumulation of the Drosophila PDGF/VEGF receptor ligands provides a mechanism for triggering localized actin polymerization.
Epithelial tissue functions depend largely on a polarized organization of the individual cells. We examined the roles of the Drosophila PDGF/VEGF receptor (PVR) in polarized epithelial cells, with specific emphasis on the wing disc epithelium. Although the receptor is broadly distributed in this tissue, two of its ligands, PVF1 and PVF3 are specifically deposited within the apical extracellular space, implying that polarized apical activation of the receptor takes place. The apical localization of the ligands involves a specialized secretion pathway. Clones for null alleles of Pvr or expression of RNAi constructs showed no phenotypes in the wing disc or pupal wing, suggesting that Pvr plays a redundant role in this tissue. However, when uniform expression of a constitutively dimerizing receptor was induced, loss of epithelial polarity, formation of multiple adherens and septate junctions, and tumorous growth were observed in the wing disc. Elevation of the level of full-length PVR also gave rise to prominent phenotypes, characterized by higher levels of actin microfilaments at the basolateral areas of the cells and irregular folding of the tissue. Together, these results suggest that polarized PVR activation is necessary for the proper organization of the wing disc epithelium, by regulating the apical assembly of the actin cytoskeleton.
Rosin
Dalia
D
Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel.
Schejter
Eyal
E
Volk
Talila
T
Shilo
Ben-Zion
BZ
D000199:Actins / Q000378:metabolism*; D000818:Animals; D016764:Cell Polarity; D003599:Cytoskeleton / Q000378:metabolism; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000033:anatomy & histology / Q000196:embryology* / Q000378:metabolism; D004527:Egg Proteins / Q000235:genetics / Q000378:metabolism*; D004628:Embryonic Structures / Q000033:anatomy & histology / Q000502:physiology*; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism*; D006493:Heparin / Q000378:metabolism; D008024:Ligands; D010641:Phenotype; D010982:Platelet-Derived Growth Factor / Q000378:metabolism; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism; D014921:Wings, Animal / Q000033:anatomy & histology / Q000196:embryology
D000199:Actins; D029721:Drosophila Proteins; D004527:Egg Proteins; D008024:Ligands; C487426:PVF3 protein, Drosophila; D010982:Platelet-Derived Growth Factor; C438367:Pvf1 protein, Drosophila; D011993:Recombinant Fusion Proteins; D042461:Vascular Endothelial Growth Factor A; D006493:Heparin; C438368:Pvr protein, Drosophila; D020794:Receptor Protein-Tyrosine Kinases