The semaphorin 4D receptor controls invasive growth by coupling with Met.
Semaphorins are cell surface and soluble signals that control axonal guidance. Recently, semaphorin receptors (plexins) have been discovered and shown to be widely expressed. Their biological activities outside the nervous system and the signal transduction mechanism(s) they utilize are largely unknown. Here, we show that in epithelial cells, Semaphorin 4D (Sema 4D) triggers invasive growth, a complex programme that includes cell#150;cell dissociation, anchorage-independent growth and branching morphogenesis. Interestingly, the same response is also controlled by scatter factors through their tyrosine kinase receptors, which share striking structural homology with plexins in their extracellular domain. We found that in cells expressing the endogenous proteins, Plexin B1 (the Sema 4D Receptor) and Met (the Scatter Factor 1/ Hepatocyte Growth Factor Receptor) associate in a complex. In addition, binding of Sema 4D to Plexin B1 stimulates the tyrosine kinase activity of Met, resulting in tyrosine phosphorylation of both receptors. Finally, cells lacking Met expression do not respond to Sema 4D unless exogenous Met is expressed. This work identifies a novel biological function of semaphorins and suggests the involvement of an unexpected signalling mechanism, namely, the coupling of a plexin to a tyrosine kinase receptor.
Institute for Cancer Research and Treatment, University of Torino School of Medicine, 10060 Candiolo, Torino, Italy. sgiordarno@ircc.unito.it
Silvia
S
Giordano
Simona
S
Corso
Paolo
P
Conrotto
Stefania
S
Artigiani
Giorgio
G
Gilestro
Davide
D
Barberis
Luca
L
Tamagnone
Paolo M
PM
Comoglio
D000595:Amino Acid Sequence; D000818:Animals; D015703:Antigens, CD; D001483:Base Sequence; D002455:Cell Division; D002460:Cell Line; D018076:DNA, Complementary / Q000235:genetics; D022781:Hepatocytes / Q000166:cytology / Q000502:physiology; D008562:Membrane Glycoproteins / Q000502:physiology*; D051379:Mice; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000502:physiology; D010766:Phosphorylation; D011485:Protein Binding; D019859:Proto-Oncogene Proteins c-met / Q000235:genetics / Q000502:physiology*; D011956:Receptors, Cell Surface / Q000502:physiology; D039961:Semaphorins; D015398:Signal Transduction; D013234:Stem Cells / Q000166:cytology / Q000502:physiology
D015703:Antigens, CD; C093224:CD100 antigen; D018076:DNA, Complementary; D008562:Membrane Glycoproteins; D009419:Nerve Tissue Proteins; C492118:Plxnb1 protein, mouse; D011956:Receptors, Cell Surface; D039961:Semaphorins; D019859:Proto-Oncogene Proteins c-met