Inhibition of collagen-induced platelet aggregation by anopheline antiplatelet protein, a saliva protein from a malaria vector mosquito.
During blood feeding, mosquitoes inject saliva containing a mixture of molecules that inactivate or inhibit various components of the hemostatic response to the bite injury as well as the inflammatory reactions produced by the bite, to facilitate the ingestion of blood. However, the molecular functions of the individual saliva components remain largely unknown. Here, we describe anopheline antiplatelet protein (AAPP) isolated from the saliva of Anopheles stephensi, a human malaria vector mosquito. AAPP exhibited a strong and specific inhibitory activity toward collagen-induced platelet aggregation. The inhibitory mechanism involves direct binding of AAPP to collagen, which blocks platelet adhesion to collagen and inhibits the subsequent increase in intracellular Ca(2+) concentration ([Ca(2+)]i). The binding of AAPP to collagen effectively blocked platelet adhesion via glycoprotein VI (GPVI) and integrin alpha(2)beta(1). Cell adhesion assay showed that AAPP inhibited the binding of GPVI to collagen type I and III without direct effect on GPVI. Moreover, intravenously administered recombinant AAPP strongly inhibited collagen-induced platelet aggregation ex vivo in rats. In summary, AAPP is a malaria vector mosquito-derived specific antagonist of receptors that mediate the adhesion of platelets to collagen. Our study may provide important insights for elucidating the effects of mosquito blood feeding against host hemostasis.
Division of Medical Zoology, Department of Infection and Immunity, Jichi Medical University, Tochigi, Japan. shigeto@jichi.ac.jp
Shigeto
S
Yoshida
Toshiki
T
Sudo
Masashi
M
Niimi
Lian
L
Tao
Bing
B
Sun
Junichi
J
Kambayashi
Hiroyuki
H
Watanabe
Enjie
E
Luo
Hiroyuki
H
Matsuoka
D000818:Animals; D000852:Anopheles; D001792:Blood Platelets / Q000187:drug effects / Q000502:physiology; D003094:Collagen / Q000494:pharmacology*; D019476:Insect Proteins / Q000235:genetics / Q000494:pharmacology*; D010973:Platelet Adhesiveness / Q000187:drug effects*; D010974:Platelet Aggregation / Q000187:drug effects / Q000502:physiology*; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology*; D010980:Platelet Membrane Glycoproteins / Q000187:drug effects / Q000502:physiology*; D011485:Protein Binding; D011994:Recombinant Proteins / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012469:Salivary Glands; D012471:Salivary Proteins and Peptides / Q000235:genetics / Q000494:pharmacology*
D019476:Insect Proteins; D010975:Platelet Aggregation Inhibitors; D010980:Platelet Membrane Glycoproteins; D011994:Recombinant Proteins; D012471:Salivary Proteins and Peptides; C121275:anophelin protein, Anopheles albimanus; C098341:platelet membrane glycoprotein VI; D003094:Collagen