Lp(a) particles mold fibrin-binding properties of apo(a) in size-dependent manner: a study with different-length recombinant apo(a), native Lp(a), and monoclonal antibody.
OBJECTIVE
Small-sized apolipoprotein(a) [apo(a)] isoforms with high antifibrinolytic activity are frequently found in cardiovascular diseases, suggesting a role for apo(a) size in atherothrombosis. To test this hypothesis, we sought to characterize the lysine (fibrin)-binding function of isolated apo(a) of variable sizes.


RESULTS
Recombinant apo(a) [r-apo(a)] preparations consisting of 10 to 34 kringles and a monoclonal antibody that neutralizes the lysine-binding function were produced and used in parallel with lipoprotein(a) [Lp(a)] particles isolated from plasma in fibrin-binding studies. All r-apo(a) preparations displayed similar affinity and specificity for lysine residues on fibrin regardless of size (K(d) 3.6+/-0.3 nmol/L) and inhibited the binding of plasminogen with a similar intensity (IC50 16.8+/-5.4 nmol/L). In contrast, native Lp(a) particles displayed fibrin affinities that were in inverse relationship with the apo(a) kringle number. Thus, a 15-kringle apo(a) separated from Lp(a) and a 34-kringle r-apo(a) displayed an affinity for fibrin that was higher than that in the corresponding particles (K(d) 2.5 versus 10.5 nmol/L and K(d) 3.8 versus 541 nmol/L, respectively). However, fibrin-binding specificity of the r-apo(a) preparations and the Lp(a) particles was efficiently neutralized (IC50 0.07 and 4 nmol/L) by a monoclonal antibody directed against the lysine-binding function of kringle IV-10.


CONCLUSIONS
Our data indicate that fibrin binding is an intrinsic property of apo(a) modulated by the composite structure of the Lp(a) particle.
INSERM U460, Faculté de Médecine Xavier Bichat, Paris, France.
Chantal
C
Kang
Miguel
M
Dominguez
Stéphane
S
Loyau
Toshiyuki
T
Miyata
Vincent
V
Durlach
Edouard
E
Anglés-Cano
D000911:Antibodies, Monoclonal / Q000378:metabolism*; D001053:Apolipoproteins / Q000097:blood / Q000276:immunology / Q000378:metabolism*; D001054:Apolipoproteins A / Q000097:blood / Q000737:chemistry / Q000276:immunology / Q000378:metabolism*; D053241:Apoprotein(a); D001666:Binding Sites, Antibody / Q000276:immunology; D001667:Binding, Competitive / Q000276:immunology; D002460:Cell Line; D005337:Fibrin / Q000378:metabolism*; D006801:Humans; D007668:Kidney / Q000166:cytology / Q000196:embryology; D018082:Kringles / Q000276:immunology; D017270:Lipoprotein(a) / Q000097:blood / Q000276:immunology / Q000378:metabolism*; D008970:Molecular Weight; D010958:Plasminogen / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding / Q000276:immunology; D020033:Protein Isoforms / Q000096:biosynthesis / Q000737:chemistry / Q000276:immunology / Q000302:isolation & purification; D011994:Recombinant Proteins / Q000276:immunology / Q000378:metabolism*
D000911:Antibodies, Monoclonal; D001053:Apolipoproteins; D001054:Apolipoproteins A; D017270:Lipoprotein(a); D020033:Protein Isoforms; D011994:Recombinant Proteins; D005337:Fibrin; D010958:Plasminogen; D053241:Apoprotein(a)