RGD peptides induce apoptosis by direct caspase-3 activation.
Synthetic peptides containing the arginine-glycine-aspartate (RGD) motif have been used extensively as inhibitors of integrin-ligand interactions in studies of cell adhesion, migration, growth and differentiation, because the RGD motif is an integrin-recognition motif found in many ligands. Here we report that RGD-containing peptides are able to directly induce apoptosis without any requirement for integrin-mediated cell clustering or signals. We show that RGD-containing peptides enter cells and directly induce autoprocessing and enzymatic activity of procaspase-3, a pro-apoptotic protein. Using the breast carcinoma cell line MCF-7, which has a functional deletion of the caspase-3 gene, we confirm that caspase-3 is required for RGD-mediated cell death. In addition to an RGD motif, pro-caspase-3 also contains a potential RGD-binding motif, aspartate-aspartate-methionine (DDM), near the site of processing to produce the p12 and p17 subunits. On the basis of the ability of RGD-DDX interactions to trigger integrin activation, we suggest that RGD peptides induce apoptosis by triggering conformational changes that promote pro-caspase-3 autoprocessing and activation. These findings provide an alternative molecular explanation for the potent proapoptotic properties of RGD peptides in models of angiogenesis, inflammation and cancer metastasis.
Division of Immunity and Infection, MRC Centre for Immune Regulation, The University of Birmingham, UK.
C D
CD
Buckley
D
D
Pilling
N V
NV
Henriquez
G
G
Parsonage
K
K
Threlfall
D
D
Scheel-Toellner
D L
DL
Simmons
A N
AN
Akbar
J M
JM
Lord
M
M
Salmon
D000595:Amino Acid Sequence; D017209:Apoptosis; D053148:Caspase 3; D020169:Caspases / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D004789:Enzyme Activation; D004792:Enzyme Precursors / Q000378:metabolism; D006801:Humans; D016023:Integrins / Q000378:metabolism; D019169:Jurkat Cells; D008214:Lymphocytes / Q000166:cytology / Q000187:drug effects; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000494:pharmacology*; D011499:Protein Processing, Post-Translational; D014407:Tumor Cells, Cultured
D004792:Enzyme Precursors; D016023:Integrins; D009842:Oligopeptides; C047981:arginyl-glycyl-aspartic acid; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases