title: ARF6-dependent activation of ERK and Rac1 modulates epithelial tubule development.
abstract: Tubules are the building blocks of epithelial organs and form in response to cues derived from morphogens such as hepatocyte growth factor (HGF). Relatively little is known about signaling pathways that orchestrate the cellular behaviors that constitute tubule development. Here, using three-dimensional cell cultures of Madin-Darby canine kidney cells, we show that the ARF6 GTPase is a critical determinant of tubule initiation in response to HGF. ARF6 is transiently activated during tubulogenesis and perturbing the ARF6 GTP/GDP cycle by inducible expression of ARF6 mutants defective in GTP binding or hydrolysis, inhibits the development of mature tubules. Further, we show that activation of ARF6 is necessary and sufficient to initiate tubule extension. The effect of ARF6 on tubule initiation is two-fold. First, ARF6 regulates the subcellular distribution of the GTPase, Rac1, to tubule extensions. Second, ARF6-induced ERK activation regulates Rac1 activation during tubule initiation through the expression of the receptor for urokinase type plasminogen activator. Thus, we have identified a cellular apparatus downstream of ARF6 activation, which regulates membrane and cytoskeleton remodeling necessary for the early stages of tubule development.
authors.affiliation: Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46656, USA.
authors.forename: Jogender Singh
authors.initials: JS
authors.lastname: Tushir
authors.forename: Crislyn
authors.initials: C
authors.lastname: D'Souza-Schorey
mesh_terms: D000089982:ADP-Ribosylation Factor 6; D020727:ADP-Ribosylation Factors / Q000378:metabolism*; D000818:Animals; D004285:Dogs; D004789:Enzyme Activation; D004848:Epithelium / Q000254:growth & development*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D005786:Gene Expression Regulation; D006153:Guanosine Diphosphate / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D008954:Models, Biological; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism; D055293:Receptors, Urokinase Plasminogen Activator; D015398:Signal Transduction; D020830:rac1 GTP-Binding Protein / Q000378:metabolism*
chemical_list: D000089982:ADP-Ribosylation Factor 6; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D055293:Receptors, Urokinase Plasminogen Activator; D006153:Guanosine Diphosphate; D006160:Guanosine Triphosphate; D048049:Extracellular Signal-Regulated MAP Kinases; D020727:ADP-Ribosylation Factors; D020830:rac1 GTP-Binding Protein