Mammalian NOTCH-1 activates beta1 integrins via the small GTPase R-Ras.
Notch is a central regulator of important cell fate decisions. Notch activation produces diverse cellular effects suggesting the presence of context-dependent control mechanisms. Genetic studies have demonstrated that Notch and integrin mutations have related phenotypes in key developmental processes such as vascular development and somitogenesis. We show that the intracellular domain of mammalian Notch-1 activates integrins without affecting integrin expression. Integrin activation is dependent on gamma-secretase-mediated intramembranous cleavage of membrane-bound Notch releasing intracellular Notch that activates R-Ras, independent of CSL-transcription. Notch also reverses H-Ras and Raf-mediated integrin suppression without affecting ERK phosphorylation. Membrane-bound Notch mutants that are inefficiently cleaved or intracellular Notch mutants lacking the ankyrin repeat sequence do not activate R-Ras or integrins. Co-expression of Msx2-interacting nuclear target (MINT) protein with Notch or expression of intracellular Notch-1 truncation mutants lacking the C-terminal transactivation/PEST domain suppresses Notch transcriptional activity without affecting integrin activation. Notch ligand, Delta-like ligand-4, stimulates R-Ras-dependent alpha 5 beta 1 integrin-mediated adhesion, demonstrating the physiological relevance of this pathway. This new CSL-independent Notch/R-Ras pathway provides a molecular mechanism to explain Notch, integrin, and Ras cross-talk during the development of multicellular organisms.
University of Edinburgh, MRC Centre for Inflammation Research, Queen's Medical Research Institute, 47 Little France Crescent, Edinburgh EH16 4SA, Scotland, United Kingdom.
Philip S
PS
Hodkinson
University of Edinburgh, MRC Centre for Inflammation Research, Queen's Medical Research Institute, 47 Little France Crescent, Edinburgh EH16 4SA, Scotland, United Kingdom.
Paul A
PA
Elliott
University of Edinburgh, MRC Centre for Inflammation Research, Queen's Medical Research Institute, 47 Little France Crescent, Edinburgh EH16 4SA, Scotland, United Kingdom.
Yatish
Y
Lad
University of Edinburgh, MRC Centre for Inflammation Research, Queen's Medical Research Institute, 47 Little France Crescent, Edinburgh EH16 4SA, Scotland, United Kingdom.
Brian J
BJ
McHugh
University of Edinburgh, MRC Centre for Inflammation Research, Queen's Medical Research Institute, 47 Little France Crescent, Edinburgh EH16 4SA, Scotland, United Kingdom.
Alison C
AC
MacKinnon
University of Edinburgh, MRC Centre for Inflammation Research, Queen's Medical Research Institute, 47 Little France Crescent, Edinburgh EH16 4SA, Scotland, United Kingdom.
Christopher
C
Haslett
University of Edinburgh, MRC Centre for Inflammation Research, Queen's Medical Research Institute, 47 Little France Crescent, Edinburgh EH16 4SA, Scotland, United Kingdom. Electronic address: t.sethi@ed.ac.uk.
Tariq
T
Sethi
D053829:Amyloid Precursor Protein Secretases / Q000235:genetics / Q000378:metabolism; D000818:Animals; D016466:CHO Cells; D002448:Cell Adhesion / Q000502:physiology; D006224:Cricetinae; D003412:Cricetulus; D004268:DNA-Binding Proteins; D048049:Extracellular Signal-Regulated MAP Kinases / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D051819:Immunoglobulin J Recombination Signal Sequence-Binding Protein / Q000235:genetics / Q000378:metabolism; D039081:Integrin alpha5beta1 / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary / Q000502:physiology; D016283:Proto-Oncogene Proteins p21(ras) / Q000235:genetics / Q000378:metabolism; D016601:RNA-Binding Proteins; D051881:Receptor, Notch1 / Q000235:genetics / Q000378:metabolism*; D018631:ras Proteins / Q000235:genetics / Q000378:metabolism*
D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; D051819:Immunoglobulin J Recombination Signal Sequence-Binding Protein; D039081:Integrin alpha5beta1; D009124:Muscle Proteins; C497761:NOTCH1 protein, human; C497762:Notch1 protein, mouse; D009687:Nuclear Proteins; C497570:RBPJ protein, human; D016601:RNA-Binding Proteins; D051881:Receptor, Notch1; C476510:SPEN protein, human; C499035:Smpx protein, mouse; C121253:Spen protein, mouse; D048049:Extracellular Signal-Regulated MAP Kinases; D053829:Amyloid Precursor Protein Secretases; C085929:RRAS protein, human; C513254:Rras protein, mouse; C495971:Hras protein, mouse; D016283:Proto-Oncogene Proteins p21(ras); D018631:ras Proteins