Ligand switching in cell-permeable peptides: manipulation of the alpha-integrin signature motif.
A synthetic cell-permeable peptide corresponding to the highly conserved alpha-integrin signature motif, Palmityl-K(989)VGFFKR(995) (Pal-FF), induces integrin activation and aggregation in human platelets. Systematic replacement of the F(992)-F(993) with amino acids of greater or lesser hydrophobicity to create Pal-KVGxxKR peptides demonstrate that hydrophobic amino acids (isoleucine, phenylalanine, tyrosine, tryptophan) are essential for agonist potency. In marked contrast, substitution with small and/or hydrophilic amino acids (glycine, alanine, serine) causes a switch in the biological activity resulting in inhibition of platelet aggregation, adhesion, ADP secretion, and thromboxane synthesis. These substituted, hydrophilic peptides are not true pharmacological antagonists, as they actively induce a phosphotyrosine signaling cascade in platelets. Singly substituted peptides (Pal-AF and Pal-FA) cause preferential retention of pro- or anti-thrombotic properties, respectively. Because the alpha-integrin signature motif is an established docking site for a number of diverse cytoplasmic proteins, we conclude that eliminating critical protein-protein interactions mediated through the hydrophobic amino acids, especially F(993), favors an anti-thrombotic pathway in platelets. Agents derived from the inhibitory peptides described in this study may represent a new therapeutic strategy for anti-platelet or anti-integrin drug development.
Bernard
Elise
E
Molecular & Cellular Therapeutics, Royal College of Surgeons in Ireland, Dublin 2, Ireland.
Parthasarathi
Laavanya
L
Cho
Min-Kyu
MK
Aylward
Kelly
K
Raab
Markus
M
Daxecker
Heide
H
O'Dushlaine
Colm T
CT
Shields
Denis C
DC
Devocelle
Marc
M
Keyes
Tia
T
Cosgrave
Lynda
L
O'Neill
Sarah
S
Mok
Kenneth H
KH
Moran
Niamh
N
D002448:Cell Adhesion / Q000187:drug effects; D002463:Cell Membrane Permeability; D006801:Humans; D039001:Integrin alpha Chains / Q000737:chemistry* / Q000378:metabolism*; D008024:Ligands; D010455:Peptides / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology*; D010974:Platelet Aggregation / Q000187:drug effects
D039001:Integrin alpha Chains; D008024:Ligands; D010455:Peptides