title: Endocytic deficiency induced by ITSN-1s knockdown alters the Smad2/3-Erk1/2 signaling balance downstream of Alk5.
abstract: Recently, we demonstrated in cultured endothelial cells and in vivo that deficiency of an isoform of intersectin-1, ITSN-1s, impairs caveolae and clathrin-mediated endocytosis and functionally upregulates compensatory pathways and their morphological carriers (i.e. enlarged endocytic structures, membranous rings or tubules) that are normally underrepresented. We now show that these endocytic structures internalize the broadly expressed transforming growth factor β receptor I (TGFβ-RI or TGFBR1), also known as Alk5, leading to its ubiquitylation and degradation. Moreover, the apoptotic or activated vascular cells of the ITSN-1s-knockdown mice release Alk5-bearing microparticles to the systemic circulation. These interact with and transfer Alk5 to endocytosis-deficient endothelial cells, resulting in lung endothelial cell survival and phenotypic alteration towards proliferation through activation of Erk1 and Erk2 (also known as MAPK3 and MAPK1, respectively). We also show that non-productive assembly of the Alk5-Smad-SARA (Smad anchor for receptor activation, also known as ZFYVE9) signaling complex and preferential formation of the Alk5-mSos-Grb2 complex account for Erk1/2 activation downstream of Alk5 and proliferation of pulmonary endothelial cells. Taken together, our studies demonstrate a functional relationship between the intercellular transfer of Alk5 by microparticles and endothelial cell survival and proliferation, and define a novel molecular mechanism for TGFβ and Alk5-dependent Erk1/2(MAPK) signaling that is significant for proliferative signaling and abnormal growth.
authors.affiliation: Department of Pharmacology, Rush University, Chicago, IL 60612, USA.
authors.forename: Cristina
authors.initials: C
authors.lastname: Bardita
authors.affiliation: Department of Pharmacology, Rush University, Chicago, IL 60612, USA Pulmonary and Critical Care Medicine, Rush University Medical Center, Chicago, IL 60612, USA.
authors.forename: Dan N
authors.initials: DN
authors.lastname: Predescu
authors.affiliation: Department of Pharmacology, Rush University, Chicago, IL 60612, USA.
authors.forename: Fei
authors.initials: F
authors.lastname: Sha
authors.affiliation: Department of Pharmacology, Rush University, Chicago, IL 60612, USA.
authors.forename: Monal
authors.initials: M
authors.lastname: Patel
authors.affiliation: Department of Microbiology and Immunology, College of Medicine, University of Illinois at Chicago, Chicago, IL 60612, USA.
authors.forename: Ganesh
authors.initials: G
authors.lastname: Balaji
authors.affiliation: Department of Pharmacology, Rush University, Chicago, IL 60612, USA Pulmonary and Critical Care Medicine, Rush University Medical Center, Chicago, IL 60612, USA sanda_predescu@rush.edu.
authors.forename: Sanda A
authors.initials: SA
authors.lastname: Predescu
mesh_terms: D033942:Adaptor Proteins, Vesicular Transport / Q000235:genetics*; D000818:Animals; D017209:Apoptosis; D021941:Caveolae / Q000378:metabolism; D002460:Cell Line; D002470:Cell Survival; D004705:Endocytosis; D042783:Endothelial Cells / Q000378:metabolism; D055785:Gene Knockdown Techniques; D006801:Humans; D008297:Male; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D000077293:Receptor, Transforming Growth Factor-beta Type I; D018125:Receptors, Transforming Growth Factor beta / Q000378:metabolism*; D015398:Signal Transduction; D051899:Smad2 Protein / Q000378:metabolism*
chemical_list: D033942:Adaptor Proteins, Vesicular Transport; C485568:ITSN1 protein, human; D018125:Receptors, Transforming Growth Factor beta; C497782:SMAD2 protein, human; D051899:Smad2 Protein; C497783:Smad2 protein, mouse; C115919:intersectin 1; D017346:Protein Serine-Threonine Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D000077293:Receptor, Transforming Growth Factor-beta Type I; C000625841:TGFBR1 protein, human; C000625842:Tgfbr1 protein, mouse
keywords: Alternative endocytic pathway; Microparticle; Proliferation