Activation of Human Platelets by Misfolded Proteins

Laboratory of Thrombosis and Haemostasis, Department of Clinical Chemistry and Haematology, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands.
Arteriosclerosis Thrombosis and Vascular Biology (Impact Factor: 6). 08/2007; 27(7):1657-65. DOI: 10.1161/ATVBAHA.107.143479
Source: PubMed


Protein misfolding diseases result from the deposition of insoluble protein aggregates that often contain fibrils called amyloid. Amyloids are found in Alzheimer disease, atherosclerosis, diabetes mellitus, and systemic amyloidosis, which are diseases where platelet activation might be implicated.
We induced amyloid properties in 6 unrelated proteins and found that all induced platelet aggregation in contrast to fresh controls. Amyloid-induced platelet aggregation was independent of thromboxane A2 formation and ADP secretion but enhanced by feedback stimulation through these pathways. Treatments that raised cAMP (iloprost), sequestered Ca2+ (BAPTA-AM) or prevented amyloid-platelet interaction (sRAGE, tissue-type plasminogen activator [tPA]) induced almost complete inhibition. Modulation of the function of CD36 (CD36-/- mice), p38(MAPK) (SB203580), COX-1 (indomethacin), and glycoprotein Ib alpha (Nk-protease, 6D1 antibody) induced approximately 50% inhibition. Interference with fibrinogen binding (RGDS) revealed a major contribution of alphaIIb beta3-independent aggregation (agglutination).
Protein misfolding resulting in the appearance of amyloid induces platelet aggregation. Amyloid activates platelets through 2 pathways: one is through CD36, p38(MAPK), thromboxane A2-mediated induction of aggregation; the other is through glycoprotein Ib alpha-mediated aggregation and agglutination. The platelet stimulating properties of amyloid might explain the enhanced platelet activation observed in many diseases accompanied by the appearance of misfolded proteins with amyloid.

Download full-text


Available from: Eszter Herczenik
  • Source
    • "RAGE and its ligands are expressed by malignant cells as well as other cells within the tumor microenvironment including leukocytes, endothelial cells, fibroblasts and platelets. These ligands can act not only in an autocrine fashion but also in a paracrine manner over many RAGE-positive cells, promoting tumor growth, angiogenesis and metastasis [25] [26] [27] [28] [29] [30] [31] [32] [33] [34]. Additionally, these ligands in the tumor microenvironment can activate platelet, promoting thrombus formation in patients with cancer [35] [36] [37] [38] [39]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: While platelets are well known to play a central role in hemostasis and thrombosis, there is emerging experimental evidence to suggest that they also mediate tumor cell growth, angiogenesis and metastasis. The receptor for advanced glycation end products (RAGE) has been extensively reported in many tumor types and initiates a downstream proinflammatory signaling cascade. RAGE ligands are expressed and secreted by tumor cells and are associated with poorer outcomes in a wide variety of tumors. In addition RAGE has been identified on human platelets and RAGE ligands may contribute to platelet activation. Therefore in the tumor microenvironment, upon activation, activated platelets interact with tumor cells through paracrine signaling and direct contact, thereby promoting tumor cell growth and thrombosis. Therefore, according to what is mentioned in this article, RAGE expression and its ligands could be a useful serological biomarker for diagnosis and treatment of cancer, as well as molecular target for novel forms of therapies.
    Full-text · Article · Jan 2016 · Blood reviews
  • Source
    • "The mechanism by which Ab peptides trigger platelet activation is unknown. A previous study has demonstrated that aggregated Ab peptides, as other misfolded proteins, induce platelet activation through two different pathways initiated by CD36 or GPIb, respectively [7]. Shen and collaborators have demonstrated that the ability of Ab 1–40 to promote platelet activation and to potentiate the effect of weak agonists is completely conserved by the smaller Ab 25–35 peptide, a fragment of 11 amino acids corresponding to the intermembrane segment of the entire peptide [8]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Accumulation of amyloidogenic Aβ peptides in the brain contributes to the onset of Alzheimer disease. Aβ peptide deposits are also present in blood vessel walls, mainly deriving from circulating platelets. However, their effect on platelet function is unclear. We demonstrate that immobilized Aβ peptides induce platelet adhesion and spreading through metalloproteinase-sensitive surface receptors. Aβ peptides also fasten platelet spreading on collagen, and support the time- and ADP-dependent activation of adherent platelets, leading to stimulation of several signalling proteins. Our results indicate a potential role for peripheral Aβ peptides in promoting platelet adhesion and activation in the initiation of thrombus formation.
    Full-text · Article · Jul 2013 · FEBS letters
  • Source
    • "In this study, we purified platelet membrane proteins for quantitative proteomics and identify potential biomarkers and pathways affected in patients with clinically diagnosed AD. In line with previous findings, many of the platelet-specific pathways that are changing are involved in platelet activation, and this is consistent with a role for Aβ peptide in activating platelets and leading to platelet aggregation [47]; moreover, APP from platelets is a major source of Aβ in circulating blood [15,100], suggesting a potential feed-forward mechanism since APP is established to be an alpha granule component [101], and its mobilization via platelet activation could lead to increased circulating Aβ. We did not sequence any APP Aβ peptide in the extracted membrane proteome, although APP was sequenced by eight peptides distributed across residues 41 to 662 in the total platelet proteome, suggesting that amyloid processing may occur in vitro during or prior to the membrane enrichment process and consistent with the presence in platelets of the full complement of secretase activities [18]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Introduction Peripheral biomarkers to diagnose Alzheimer's disease (AD) have not been established. Given parallels between neuron and platelet biology, we hypothesized platelet membrane-associated protein changes may differentiate patients clinically defined with probable AD from noncognitive impaired controls. Methods Purified platelets, confirmed by flow cytometry were obtained from individuals before fractionation by ultracentrifugation. Following a comparison of individual membrane fractions by SDS-PAGE for general proteome uniformity, equal protein weight from the membrane fractions for five representative samples from AD and five samples from controls were pooled. AD and control protein pools were further divided into molecular weight regions by one-dimensional SDS-PAGE, prior to digestion in gel. Tryptic peptides were analyzed by reverse-phase liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). Ionized peptide intensities were averaged for each identified protein in the two pools, thereby measuring relative protein abundance between the two membrane protein pools. Log2-transformed ratio (AD/control) of protein abundances fit a normal distribution, thereby permitting determination of significantly changed protein abundances in the AD pool. Results We report a comparative analysis of the membrane-enriched platelet proteome between patients with mild to moderate AD and cognitively normal, healthy subjects. A total of 144 proteins were determined significantly altered in the platelet membrane proteome from patients with probable AD. In particular, secretory (alpha) granule proteins were dramatically reduced in AD. Of these, we confirmed significant reduction of thrombospondin-1 (THBS1) in the AD platelet membrane proteome by immunoblotting. There was a high protein-protein connectivity of proteins in other pathways implicated by proteomic changes to the proteins that define secretory granules. Conclusions Depletion of secretory granule proteins is consistent with a preponderance of post-activated platelets in circulation in AD. Significantly changed pathways implicate additional AD-related defects in platelet glycoprotein synthesis, lipid homeostasis, amyloidogenic proteins, and regulators of protease activity, many of which may be useful plasma membrane-expressed markers for AD. This study highlights the utility of LC-MS/MS to quantify human platelet membrane proteins and suggests that platelets may serve as a source of blood-based biomarkers in neurodegenerative disease.
    Full-text · Article · Jun 2013 · Alzheimer's Research and Therapy
Show more