RGD-mutants of B-lymphotropic polyomavirus capsids specifically bind to alpha(v)beta3 integrin.
Integrins are a family of cell surface proteins that function as receptors for extracellular matrix ligands and for some viruses. A subset of integrins recognises peptide sequences containing arginine-glycine-aspartic acid (RGD) motifs as ligands. The B-lymphotropic polyomavirus (LPV) has a non-enveloped capsid that recognises a sialylated cell surface receptor. To change the receptor binding specificity we have replaced sets of three amino acids in three predicted surface loops of the major capsid protein VP1 of the B-lymphotropic polyomavirus LPV by RGD. Ten mutants gave rise to the expected 40 kDa VP1 protein upon expression from a baculovirus vector in insect cells. Five of the VP1 mutants representing all three surface loops have retained the ability to spontaneously assemble to capsids in the nuclei of the insect cells. Structural changes of the mutant capsid surface were shown by differential reactivity with a set of 7 neutralising monoclonal antibodies that recognise conformational surface epitopes of wildtype LPV virions. In addition all mutant capsids had lost specific binding to the LPV receptor. Three mutant capsids of one loop (BC) showed specific binding to alpha(v)beta3 integrin but not to integrins alpha(v)beta5, alpha(v)beta6, or to alpha(IIb)beta3 known also to recognise RGD containing peptide sequences. This selective binding of the mutant capsids could be inhibited by synthetic peptides that specifically bind to alpha(v)beta3 integrin with IC50 values between 10 and 40 nM.
Langner
J
J
Research Program Infection and Cancer, Deutsches Krebsforschungszentrum, Heidelberg, Germany.
Neumann
B
B
Goodman
S L
SL
Pawlita
M
M
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D036022:Capsid Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D039302:Integrin alphaVbeta3 / Q000378:metabolism*; D016023:Integrins / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D020125:Mutation, Missense; D009842:Oligopeptides / Q000235:genetics / Q000378:metabolism*; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000378:metabolism*; D011120:Polyomavirus / Q000235:genetics*; D011485:Protein Binding; D011487:Protein Conformation; D011991:Receptors, Virus / Q000378:metabolism; D019030:Receptors, Vitronectin / Q000378:metabolism; D013539:Simian virus 40; D019065:Virus Assembly
D036022:Capsid Proteins; D039302:Integrin alphaVbeta3; D016023:Integrins; D009842:Oligopeptides; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D011991:Receptors, Virus; D019030:Receptors, Vitronectin; C062481:VP1 protein, polyomavirus; C064660:integrin alphaVbeta5; C047981:arginyl-glycyl-aspartic acid