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.
Buckley
C D
CD
Division of Immunity and Infection, MRC Centre for Immune Regulation, The University of Birmingham, UK.
Pilling
D
D
Henriquez
N V
NV
Parsonage
G
G
Threlfall
K
K
Scheel-Toellner
D
D
Simmons
D L
DL
Akbar
A N
AN
Lord
J M
JM
Salmon
M
M
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