The original Pathologische Anatomie Leiden-Endothelium monoclonal antibody recognizes a vascular endothelial growth factor binding site within neuropilin-1.
For two decades, the antigen recognized by the Pathologische Anatomie Leiden-Endothelium (PAL-E) monoclonal antibody, a standard vascular endothelial cell marker, has remained elusive. Here, we used a combinatorial phage display-based approach ("epitope mapping") to select peptides binding to the original PAL-E antibody. We found that a subset of the selected panel of peptides had motifs with strong homology to an exposed site within the b1 domain of human neuropilin-1 (NRP-1). We confirmed peptide binding by ELISA and by surface plasmon resonance. We also showed that the PAL-E antigen colocalizes with NRP-1 staining in endothelial cells. Crystal structure of the b1 domain in NRP-1 suggests that the PAL-E binding site overlaps with a vascular endothelial growth factor (VEGF) binding site. Taken together, these results indicate that NRP-1 is an endothelial cell antigen recognized by the true PAL-E antibody. The consistent biochemical, morphologic, and functional features between the PAL-E antigen and NRP-1 support our interpretation. Given that NRP-1 is a VEGF receptor, these results explain the attributes of the PAL-E antibody as a marker of vascular permeability and angiogenesis.
Jaalouk
Diana E
DE
The University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030, USA.
Ozawa
Michael G
MG
Sun
Jessica
J
Lahdenranta
Johanna
J
Schlingemann
Reinier O
RO
Pasqualini
Renata
R
Arap
Wadih
W
D000595:Amino Acid Sequence; D000911:Antibodies, Monoclonal / Q000276:immunology*; D001666:Binding Sites, Antibody; D002478:Cells, Cultured; D020650:Combinatorial Chemistry Techniques; D042783:Endothelial Cells / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D018604:Epitope Mapping; D006801:Humans; D008958:Models, Molecular; D039942:Neuropilin-1 / Q000276:immunology* / Q000378:metabolism; D019151:Peptide Library; D010455:Peptides / Q000276:immunology* / Q000378:metabolism; D020349:Surface Plasmon Resonance; D042461:Vascular Endothelial Growth Factor A / Q000276:immunology* / Q000378:metabolism
D000911:Antibodies, Monoclonal; D019151:Peptide Library; D010455:Peptides; C467484:VEGFA protein, human; D042461:Vascular Endothelial Growth Factor A; D039942:Neuropilin-1