The RGD integrin binding site in human L1-CAM is important for nuclear signaling.
L1 cell adhesion molecule (L1-CAM) is a transmembrane cell adhesion molecule initially defined as a promigratory molecule in the developing nervous system. L1 is also overexpressed in a variety of human carcinomas and is associated with bad prognosis. In carcinoma cell lines L1 augments cell motility and metastasis, tumor growth in nude mice and induces expression of L1-dependent genes. It is not known whether L1-signaling requires ligand binding. The RGD motif in the sixth Ig domain of L1 is a binding site for integrins. In the present study we analyzed the role of RGDs in L1-signaling using site-directed mutagenesis combined with antibody blocking studies. We observed that L1-RGE expressing HEK293 cells showed reduced cell-cell binding, cell motility, invasiveness and tumor growth in NOD/SCID mice. The RGE-mutation impaired L1-dependent gene regulation and antibodies to alphavbeta5 integrin had similar effects. Mutant L1 was unable to translocate to the nucleus. Our findings highlight the importance of the RGD site in L1 for human tumors and suggest that nuclear signaling of L1 is dependent on integrins.
Tumor Immunology Programme, D010, German Cancer Research Center, Heidelberg, Germany.
Daniela
D
Gast
Svenja
S
Riedle
Helena
H
Kiefel
Susanne Sebens
SS
Müerköster
Heiner
H
Schäfer
Michael K E
MK
Schäfer
Peter
P
Altevogt
D021581:Active Transport, Cell Nucleus / Q000235:genetics; D000818:Animals; D001665:Binding Sites / Q000235:genetics / Q000502:physiology; D016466:CHO Cells; D002448:Cell Adhesion / Q000235:genetics; D002450:Cell Communication / Q000235:genetics; D002465:Cell Movement / Q000235:genetics; D002467:Cell Nucleus / Q000378:metabolism*; D002478:Cells, Cultured; D006224:Cricetinae; D003412:Cricetulus; D005260:Female; D017353:Gene Deletion; D005786:Gene Expression Regulation; D006801:Humans; D016023:Integrins / Q000378:metabolism*; D051379:Mice; D016688:Mice, Inbred NOD; D016513:Mice, SCID; D039842:Neural Cell Adhesion Molecule L1 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D009842:Oligopeptides / Q000235:genetics / Q000502:physiology*; D015398:Signal Transduction; D014183:Transplantation, Heterologous
D016023:Integrins; D039842:Neural Cell Adhesion Molecule L1; D009842:Oligopeptides; C047981:arginyl-glycyl-aspartic acid