Inhibition of PDGF-B induction and cell growth by syndecan-1 involves the ubiquitin and SUMO-1 ligase, Topors.
Syndecans are receptors for soluble ligands, including heparin-binding growth factors, and matrix proteins. However, intracellular targets of syndecan-1 (Sdc-1)-mediated signaling are not fully understood. A yeast two-hybrid protein interaction screening of a mouse embryo library identified the ubiquitin and SUMO-1 E3 ligase, Topors, as a novel ligand of the Sdc-1 cytoplasmic domain (S1CD), a finding confirmed by ligand blotting and co-precipitation with Sdc-1 from cell lysates. Deletion mutagenesis identified an 18-amino acid sequence of Topors required for the interaction with the S1CD. By immunohistochemistry, Topors and Sdc-1 co-localized near the cell periphery in normal murine mammary gland (NMuMG) cells in vitro and in mouse embryonic epithelia in vivo. Finally, siRNA-mediated knockdown of Topors demonstrated that Topors is a growth promoter for murine arterial smooth muscle cells and is required for the inhibitory effect of Sdc-1 on cell growth and platelet-derived growth factor-B induction. These data suggest a novel mechanism for the inhibitory effects of Sdc-1 on cell growth that involves the interaction between the cytoplasmic domain of Sdc-1 and the SUMO-1 E3 ligase, Topors.
Benaroya Research Institute at Virginia Mason, Seattle, Washington, United States of America.
Kathleen R
KR
Braun
Allison M
AM
DeWispelaere
Steven L
SL
Bressler
Nozomi
N
Fukai
Richard D
RD
Kenagy
Lihua
L
Chen
Alexander W
AW
Clowes
Michael G
MG
Kinsella
D000818:Animals; D001665:Binding Sites / Q000235:genetics; D015153:Blotting, Western; D002460:Cell Line; D049109:Cell Proliferation; D002478:Cells, Cultured; D047468:Immunoprecipitation; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009154:Mutation; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000378:metabolism; D041681:NIH 3T3 Cells; D011485:Protein Binding; D020574:Proto-Oncogene Proteins c-sis / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D053668:Syndecan-1 / Q000235:genetics / Q000378:metabolism*; D013917:Thrombin / Q000494:pharmacology; D020798:Two-Hybrid System Techniques; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*
D020574:Proto-Oncogene Proteins c-sis; D053668:Syndecan-1; C550140:Topors protein, mouse; D044767:Ubiquitin-Protein Ligases; D013917:Thrombin