Human platelet 12-lipoxygenase: Naturally occurring Q261/R261 variants and N544L mutant show altered activity but unaffected substrate binding and membrane association behavior

SummaryWe have observed that naturally occurring serum antibodies generated a 30 Kd band in a platelet immunoblot assay. The target protein had the same molecular weight (30 Kd) under nonreduced and reduced electrophoretic conditions, and could be immunoblotted from either autologous or homologous platelet lysates. Also, the 30 Kd reactive autoantibodies could be totally adsorbed by platelet cytoskeletons. From these data one likely candidate for the autoantibody target was the intracellular platelet protein tropomyosin. Indeed, a commercially available monoclonal antitropomyosin antibody reacted with proteins comigrating with this 30 Kd band; affinity purified human platelet tropomyosin was bound by the antibodies that recognized the 30 Kd protein. This body of evidence conclusively demonstrated that naturally occurring serum autoantibodies reacted with the platelet cytoskeleton protein - tropomyosin. These tropomyosin specific antibodies were found in roughly the same percentage of sera from patients with chronic idiopathic thrombocytopenic purpura (ITP) as from normal individuals.

Download Full-text

Discovery of Potent and Selective Inhibitors of Human Platelet-Type 12- Lipoxygenase

Journal of Medicinal Chemistry ◽

10.1021/jm2005089 ◽

2011 ◽

Vol 54 (15) ◽

pp. 5485-5497 ◽

Cited By ~ 44

Author(s):

Victor Kenyon ◽

Ganesha Rai ◽

Ajit Jadhav ◽

Lena Schultz ◽

Michelle Armstrong ◽

...

Keyword(s):

Human Platelet ◽

Selective Inhibitors ◽

12 Lipoxygenase

Download Full-text

Human Platelet 12-Lipoxygenase, New Findings about Its Activity, Membrane Binding and Low-resolution Structure

Journal of Molecular Biology ◽

10.1016/j.jmb.2007.11.086 ◽

2008 ◽

Vol 376 (1) ◽

pp. 193-209 ◽

Cited By ~ 46

Author(s):

Ansari M. Aleem ◽

Jerzy Jankun ◽

John D. Dignam ◽

Matthias Walther ◽

Hartmut Kühn ◽

...

Keyword(s):

Human Platelet ◽

Membrane Binding ◽

Low Resolution ◽

New Findings ◽

12 Lipoxygenase ◽

Resolution Structure

Download Full-text

Inhibition of platelet aggregation by protease inhibitors. Possible involvement of proteases in platelet aggregation

Blood ◽

10.1182/blood.v52.1.1.1 ◽

1978 ◽

Vol 52 (1) ◽

pp. 1-12 ◽

Cited By ~ 20

Author(s):

N Aoki ◽

K Naito ◽

N Yoshida

Keyword(s):

Platelet Aggregation ◽

Protease Inhibitors ◽

Serine Proteases ◽

Human Platelet ◽

Serotonin Release ◽

Second Phase ◽

Inhibition Of Platelet Aggregation ◽

Naturally Occurring ◽

Human Platelet Aggregation ◽

Platelet Receptor

Abstract The possible participation of proteases in human platelet aggregation was explored using various protease inhibitors and substrates. Protease inhibitors used included naturally occurring inhibitors of serine proteases and synthetic inhibitors that modify the active site of protease. Substrates used were synthetic substrates for the trypsin type as well as for the chymotrypsin type of protease. All these inhibitors and substrates inhibited platelet aggregation and serotonin release induced by ADP, collagen, epinephrine, or thrombin. In ADP- and epinephrine-induced platelet aggregation the second phase of aggregation was most efficiently inhibited. The inhibitors suppressed the formation of malondialdehyde during platelet aggregation. Release by aggregating agents of arachidonate and its metabolites from indomethacin-treated platelets as well as nontreated platelets was also inhibited. The inhibitors apperar to interact with stimulated platelets but not with unstimulated platelets. These observations suggest that the interaction of an aggregating agent with its platelet receptor activates a unique precursor serine protease that in turn activates platelet phospholipase to liberate arachidonic acid (the precursor of the potent platelet aggregating agent thromboxane A2) from platelet phospholipids.

Download Full-text