Blood relations: Nanoparticles that enter the bloodstream become coated with proteins. Four apolipoproteins are consistently recovered on model copolymer nanoparticles by using a centrifugation procedure (see electropherogram); their interaction with the nanoparticles is stronger than that of other plasma proteins with higher abundance.

Blutsverwandte: Nanopartikel, die in den Blutstrom eintreten, lagern an ihrer Oberfläche Proteine an. Vier Apolipoproteine wurden mithilfe von Copolymernanopartikeln beim Zentrifugieren vollständig zurückerhalten (siehe Elektropherogramm); ihre Wechselwirkung mit den Nanopartikeln ist stärker als die anderer Plasmaproteine, die in höheren Konzentrationen vorkommen.

Summary Background Microparticles (MPs), small vesicles shed from stimulated cells, permit cross-talk between cells within a particular environment. Their composition is thought to reflect their cell of origin, and differs according to whether they are produced by stimulation or by apoptosis. Whether MP properties vary according to stimulus is not yet known. Methods We studied the characteristics of MPs produced from monocytic THP-1 cells upon stimulation with lipopolysaccharide or a soluble P-selectin chimera, using proteomics, flow cytometry, western blotting, and electron microscopy. Results Utilizing a novel criterion of calcein-AM staining to define MPs, we found that MP populations were similar with respect to size, presence and organization of cytoskeleton, and expression of certain antigens. The MPs shared the same level of procoagulant activity. We found that MPs also have distinct characteristics, depending on stimuli. These include differences in phosphatidylserine expression and expression of proteins from specific subcellular locations such as the mitochondria, and of unique antigens such as leukocyte-associated immunoglobin-like-receptor (LAIR)-1, which was found only upon stimulation with the soluble P-selectin chimera. Conclusion We found that the properties of MPs depend on the stimulus that produced them. This supports the concept that monocytic MPs differentially modulate thrombosis, inflammation and immune regulation according to stimulus.

Wnts regulate important intracellular signaling events, and dysregulation of the Wnt pathway has been linked to human disease. Here, we uncover numerous Wnt canonical effectors in human platelets where Wnts, their receptors, and downstream signaling components have not been previously described. We demonstrate that the Wnt3a ligand inhibits platelet adhesion, activation, dense granule secretion, and aggregation. Wnt3a also altered platelet shape change and inhibited the activation of the small GTPase RhoA. In addition, we found the Wnt-␤-catenin signaling pathway to be functional in platelets. Finally, disruption of the Wnt Frizzled 6 receptor in the mouse resulted in a hyperactivatory platelet phenotype and a reduced sensitivity to Wnt3a. Taken together our studies reveal a novel functional role for Wnt signaling in regulating anucleate platelet function and may provide a tractable target for future antiplatelet therapy.Wnt-␤-catenin pathway ͉ integrin ␣IIb␤3 ͉ frizzled 6 knockout mice A nucleate platelets are the principle effectors of haemostasis and are found circulating in a nonadhesive, quiescent state. At sites of vascular damage, platelets adhere to various exposed subendothelial matrix proteins and are activated, converting from a resting, discoid shape into larger, flattened structures with extended pseudopodia (1). Such activated platelets secrete and synthesize further agonists, inflammatory mediators, and vasoactive substances and through conformational changes in their major integrin receptor, ␣IIb␤3, aggregate to other platelets via fibrinogen (Fb) to form a haemostatic plug (2). Aberrant platelet activation can cause pathological thrombus formation, leading to thrombosis and ultimately vessel occlusion and tissue ischemia, the processes underlying myocardial infarction and stroke. Understanding the regulation of platelet activity is thus fundamental to comprehending thrombotic disorders and developing therapeutic strategies.The mammalian Wnt gene family is comprised of 19 secreted Wnt glycoproteins, which play essential roles in cell proliferation, cell-fate determination, and cell-fate differentiation during embryonic development and adult homeostasis (3, 4). These Wnt ligands activate a number of different signaling pathways via distinct receptors and downstream effectors to mediate effects on gene transcription and cell adhesion/migration (5, 6). For the Wnt-␤-catenin (␤-cat) signaling pathway (Fig. 1A), traditionally referred to as the ''canonical'' pathway, Wnts bind to a surface receptor complex comprised of a Frizzled (Fzd) receptor and the Lipoprotein Receptor-related Protein 5/6 (LRP5/6) coreceptor (5, 7). The signal is then transduced to the cytoplasmic protein Dishevelled (Dvl) where downstream pathways regulate the stability of ␤-cat (5, 7). In the absence of Wnt, ␤-cat is phosphorylated by a destruction complex containing Casein Kinase 1 (CK1), Glycogen Synthase Kinase 3␤ (GSK3␤), Axin-1, FRAT-1, and Adenomatous Polyposis Coli (APC), which targets ␤-cat for degradation via ubiquitina...

Short synthetic oligopeptides based on regions of human proteins that encompass functional motifs are versatile reagents for understanding protein signaling and interactions. They can either mimic or inhibit the parent protein's activity and have been used in drug development. Peptide studies typically either derive peptides from a single identified protein or (at the other extreme) screen random combinatorial peptides, often without knowledge of the signaling pathways targeted. Our objective was to determine whether rational bioinformatic design of oligopeptides specifically targeted to potentially signaling-rich juxtamembrane regions could identify modulators of human platelet function. High-throughput in vitro platelet function assays of palmitylated cell-permeable oligopeptides corresponding to these regions identified many agonists and antagonists of platelet function. Many bioactive peptides were from adhesion molecules, including a specific CD226-derived inhibitor of inside-out platelet signaling. Systematic screens of this nature are highly efficient tools for discovering short signaling motifs in molecular signaling pathways.