Glycoprotein (GP) Ib was purified from lysates of human platelets prepared in the presence or absence of inhibitors of the endogenous calcium-activated neutral protease (CANP) by immunoaffinity chromatography, employing the GPIb-specific murine monoclonal antibody, AP1, coupled to Sepharose CL4B. When derived from lysates prepared in the presence of EDTA or leupeptin, the eluate from the AP1-af...

Bernard-Soulier syndrome (BSS) platelets, which lack the membrane glycoprotein complex Ib-IX, do not adhere to subendothelium. The adhesion of platelets from two patients with BSS to subendothelial microfibrils (MFs) and type I collagen was compared in an in vitro assay adapted to patients with low platelet count. With both patients, platelet adhesion to MFs was strongly defective, whereas the ...

BACKGROUND Animal models have been instrumental in defining thrombus formation, including the role of platelet surface glycoprotein (GP) receptors, in acute ischemic stroke (AIS). However, the involvement of GP receptors in human ischemic stroke pathophysiology and their utility as biomarkers for ischemic stroke risk and severity requires elucidation. AIMS To determine whether platelet GPIb a...

The Mr approximately 540,000 dimeric actin gelation protein, actin-binding protein (ABP), has previously been shown in human platelets to link actin to membrane glycoprotein Ib (GPIb) (Fox, J. E. B. (1985) J. Biol. Chem. 260, 11970-11977; Okita, J. R., Pidard, D., Newman, P. J., Montgomery, R. R., and Kunicki, T. J. (1985) J. Cell Biol. 100, 317-321). We have examined further the interaction be...

BACKGROUND Inhibition of early platelet adhesion by blockade of glycoprotein-IB (GPIb) protects mice from ischemic stroke. To elucidate underlying mechanisms in-vivo, infarct development was followed by ultra-high field MRI at 17.6 Tesla. METHODS Cerebral infarction was induced by transient-middle-cerebral-artery-occlusion (tMCAO) for 1 hour in C57/BL6 control mice (N = 10) and mice treated w...

Bernard-Soulier syndrome (B-Ss) is a rare congenital bleeding disorder caused by abnormal giant platelets, thrombocytopenia, and defective glycoprotein (GP) Ib-V-IX, the adhesion receptor for von Willebrand factor (vWF). This report describes the molecular defect in two related individuals with well-established B-Ss whose platelets exhibit decreased GPIb-IX and normal GPV on their surfaces. The...

OBJECTIVE The glycoprotein (GP) Ib-V-IX complex regulates the adhesion, activation, and procoagulant activity of platelets. We previously reported that RAM.1, a rat monoclonal antibody directed against the extracellular domain of mouse GPIbβ, diminished adhesion of platelets and chinese hamster ovary cells transfected with the human GPIb-IX complex to von Willebrand factor under flow conditions...

A case is reported of a 49-year-old woman with a mild bleeding tendency. Her bleeding time, platelet count and size, plasma ristocetin cofactor activity, von Willebrand factor (vWF) antigen, and vWF multimeric pattern are all within normal limits. Spontaneous platelet aggregation is observed when citrated platelet-rich plasma (PRP) is stirred in an aggregometer cuvette. This aggregation is comp...

The platelet receptor for von Willebrand factor (VWF), glycoprotein (GP) Ib-IX, mediates initial platelet adhesion and activation. It is known that the cytoplasmic domain of GPIbbeta is phosphorylated at Ser(166) by cAMP-dependent protein kinase (PKA). To understand the physiological role of GPIbbeta phosphorylation, a GPIb-IX mutant replacing Ser(166) of GPIbbeta with alanine (S166A) and a del...

Calcium-activated neutral proteinase (calpain) has been shown to cleave proteins involved in the maintenance of cell structure. In human platelets, substrates of calpain include glycoprotein Ib (GPIb), actin-binding protein (ABP), and talin. GPIb-ABP complexes can be isolated in detergent extracts and are thought to represent membrane-cytoskeleton attachment sites. It has been hypothesized that...