Glycoprotein Ibalpha-bound thrombin functions as a serine protease to produce macromolecular activators of phagocytosis from platelets.
Production of macromolecular activators of phagocytosis from platelets (MAPPs) was observed when the lysate of fresh platelets was incubated with MAPP precursors and thrombin. An 800-Da MAPP activator (PMA-II) was obtained by Superdex peptide gel filtration of the lysate after thrombin treatment. The necessity of thrombin in MAPP production in fresh platelets was confirmed by the action of anti-thrombin monoclonal antibody or anti-thrombin III and heparin. To specify the thrombin receptor on which the thrombin forming PMA-II binds, the effects of thrombin-receptor-derived peptides and anti-thrombin receptor antibodies on MAPP production by stored platelets which have lost their thrombin content were investigated. DYYPEEDTEGD involved in glycoprotein Ibalpha and anti-glycoprotein Ibalpha antibody prevented stored platelets from producing MAPP. These observations suggest that thrombin bound to glycoprotein Ibalpha functions as a serine protease in MAPP formation.
Sakamoto
H
H
2nd Department of Pathology, Kagawa Medical University, Kagawa, 761-0793, Japan.
Ueno
M
M
Yanghong
W
W
Khatun
R
R
Tanaka
S
S
Miyabe
K
K
Ogawa
Y
Y
Onodera
M
M
D000595:Amino Acid Sequence; D001792:Blood Platelets / Q000378:metabolism* / Q000648:ultrastructure; D006801:Humans; D016253:Microscopy, Immunoelectron; D008969:Molecular Sequence Data; D010587:Phagocytosis; D010980:Platelet Membrane Glycoproteins / Q000378:metabolism*; D013917:Thrombin / Q000378:metabolism*
D010980:Platelet Membrane Glycoproteins; D013917:Thrombin