Human neural cell adhesion molecule L1 and rat homologue NILE are ligands for integrin alpha v beta 3.
Integrin alpha v beta 3 is distinct in its capacity to recognize the sequence Arg-Gly-Asp (RGD) in many extra-cellular matrix (ECM) components. Here, we demonstrate that in addition to the recognition of ECM components, alpha v beta 3 can interact with the neural cell adhesion molecule L1-CAM; a member of the immunoglobulin superfamily (IgSF). M21 melanoma cells displayed significant Ca(++)-dependent adhesion and spreading on immunopurified rat L1 (NILE). This adhesion was found to be dependent on the expression of the alpha v-integrin subunit and could be significantly inhibited by an antibody to the alpha v beta 3 heterodimer. M21 cells also displayed some alpha v beta 3-dependent adhesion and spreading on immunopurified human L1. Ligation between this ligand and alpha v beta 3 was also observed to promote significant haptotactic cell migration. To map the site of alpha v beta 3 ligation we used recombinant L1 fragments comprising the entire extracellular domain of human L1. Significant alpha v beta 3-dependent adhesion and spreading was evident on a L1 fragment containing Ig-like domains 4, 5, and 6. Importantly, mutation of an RGD sequence present in the sixth Ig-like domain of L1 abrogated M21 cell adhesion. We conclude that alpha v beta 3-dependent recognition of human L1 is dependent on ligation of this RGD site. Despite high levels of L1 expression the M21 melanoma cells did not display significant adhesion via a homophilic L1-L1 interaction. These data suggest that M21 melanoma cells recognize and adhere to L1 through a mechanism that is primarily heterophilic and integrin dependent. Finally, we present evidence that melanoma cells can shed and deposit L1 in occluding ECM. In this regard, alpha v beta 3 may recognize L1 in a cell-cell or cell-substrate interaction.
Montgomery
A M
AM
Department of Immunology, Scripps Research Institute, La Jolla, California 92037, USA.
Becker
J C
JC
Siu
C H
CH
Lemmon
V P
VP
Cheresh
D A
DA
Pancook
J D
JD
Zhao
X
X
Reisfeld
R A
RA
D000595:Amino Acid Sequence; D000818:Animals; D000906:Antibodies; D000954:Antigens, Surface / Q000378:metabolism; D001483:Base Sequence; D001665:Binding Sites; D002448:Cell Adhesion; D002460:Cell Line; D002465:Cell Movement; D017931:DNA Primers; D006801:Humans; D007700:Kinetics; D039841:Leukocyte L1 Antigen Complex; D008024:Ligands; D008545:Melanoma; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D019006:Neural Cell Adhesion Molecules / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism*; D009842:Oligopeptides; D016133:Polymerase Chain Reaction; D051381:Rats; D019030:Receptors, Vitronectin / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism; D014407:Tumor Cells, Cultured
D000906:Antibodies; D000954:Antigens, Surface; D017931:DNA Primers; D039841:Leukocyte L1 Antigen Complex; D008024:Ligands; D019006:Neural Cell Adhesion Molecules; D009842:Oligopeptides; D019030:Receptors, Vitronectin; D011993:Recombinant Fusion Proteins; C047981:arginyl-glycyl-aspartic acid