Decreased numbers of dense granules in fetal and neonatal platelets.
Ontology highlight
ABSTRACT:
SUBMITTER: Urban D
PROVIDER: S-EPMC5286950 | biostudies-literature |
REPOSITORIES: biostudies-literature
Similar Datasets
Project description:Human and murine platelets (PLTs) variably express toll-like receptors (TLRs), which link the innate and adaptive immune responses during infectious inflammation and atherosclerotic vascular disease. In this paper, we show that the TLR9 transcript is specifically up-regulated during pro-PLT production and is distributed to a novel electron-dense tubular system-related compartment we have named the T granule. TLR9 colocalizes with protein disulfide isomerase and is associated with either VAMP 7 or VAMP 8, which regulates its distribution in PLTs on contact activation (spreading). Preincubation of PLTs with type IV collagen specifically increased TLR9 and CD62P surface expression and augmented oligodeoxynucleotide (ODN) sequestration and PLT clumping upon addition of bacterial/viral ODNs. Collectively, this paper (a) tracks TLR9 to a new intracellular compartment in PLTs and (b) describes a novel mechanism of TLR9 organization and signaling in human PLTs.
| S-EPMC3514030 | biostudies-literature
Project description:Platelet dense granules (DGs) are storage organelles for calcium ions, small organic molecules such as ADP and serotonin, and larger polyphosphates that are secreted upon platelet stimulation to enhance platelet activation, adhesion, and stabilization at sites of vascular damage. DGs are thought to fully mature within megakaryocytes (MKs) prior to platelet formation. Here we challenge this notion by exploiting vital fluorescent dyes to distinguish mildly acidic DGs from highly acidic compartments by microscopy in platelets and MKs. In isolated primary mouse platelets, compartments labeled by mepacrine - a fluorescent weak base that accumulates in DGs - are readily distinguishable from highly acidic compartments, likely lysosomes, that are labeled by the acidic pH indicator, LysoTracker, and from endolysosomes and alpha granules labeled by internalized and partially digested DQ™ BSA. By contrast, in murine fetal liver- and human CD34+ cell-derived MKs and the megakaryocytoid cell lines, MEG-01 and differentiated G1ME2, labeling by mepacrine overlapped nearly completely with labeling by LysoTracker and partially with labeling by DQ™ BSA. Mepacrine labeling in G1ME2-derived MKs was fully sensitive to proton ATPase inhibitors, but was only partially sensitive in platelets. These data indicate that mepacrine in MKs accumulates as a weak base in endolysosomes but is likely pumped into or retained in separate DGs in platelets. Fluorescent puncta that labeled uniquely for mepacrine were first evident in G1ME2-derived proplatelets, suggesting that DGs undergo a maturation step that initiates in the final stages of MK differentiation.
| S-EPMC5604861 | biostudies-literature
Project description:Regulated exocytosis of dense core secretory granules releases biologically active proteins in a stimulus-dependent fashion. The packaging of the cargo within newly forming granules involves a transition: soluble polypeptides condense to form water-insoluble aggregates that constitute the granule cores. Following exocytosis, the cores generally disassemble to diffuse in the cell environment. The ciliates Tetrahymena thermophila and Paramecium tetraurelia have been advanced as genetically manipulatable systems for studying exocytosis via dense core granules. However, all of the known granule proteins in these organisms condense to form the architectural units of lattices that are insoluble both before and after exocytosis. Using an approach designed to detect new granule proteins, we have now identified Igr1p (induced during granule regeneration). By structural criteria, it is unrelated to the previously characterized lattice-forming proteins. It is distinct in that it is capable of dissociating from the insoluble lattice following secretion and therefore represents the first diffusible protein identified in ciliate granules.
| S-EPMC117993 | biostudies-literature
Project description:In addition to their primary roles in hemostasis and thrombosis, platelets participate in many other physiological and pathological processes, including, but not limited to inflammation, wound healing, tumor metastasis, and angiogenesis. Among their most interesting properties is the large number of bioactive proteins stored in their α-granules, the major storage granule of platelets. We previously showed that platelets differentially package pro- and antiangiogenic proteins in distinct α-granules that undergo differential release upon platelet activation. Nevertheless, how megakaryocytes achieve differential packaging is not fully understood. In this study, we use a mouse megakaryocyte culture system and endocytosis assay to establish when and where differential packaging occurs during platelet production. Live cell microscopy of primary mouse megakaryocytes incubated with fluorescently conjugated fibrinogen and endostatin showed differential endocytosis and packaging of the labeled proteins into distinct α-granule subpopulations. Super-resolution microscopy of mouse proplatelets and human whole-blood platelet α-granules simultaneously probed for 2 different membrane proteins (VAMP-3 and VAMP-8), and multiple granular content proteins (bFGF, ENDO, TSP, VEGF) confirmed differential packaging of protein contents into α-granules. These data suggest that megakaryocytes differentially sort and package α-granule contents, which are preserved as α-granule subpopulations during proplatelet extension and platelet production.
| S-EPMC6849942 | biostudies-literature
Project description:Platelet-dense (?) granules are important for platelet function. Platelets contribute to host defense and vascular integrity during pneumonia and sepsis, and ? granule products, including adenosine diphosphate (ADP), can influence inflammatory responses. We therefore aimed to study the role of platelet ? granules in the host response during sepsis. Hermansky-Pudlak syndrome (Hps)3coa mice (with reduced ? granule content), mice treated with the platelet ADP receptor inhibitor clopidogrel, and appropriate control mice were infected with the human sepsis pathogen Klebsiella pneumoniae via the airways to induce pneumonia and sepsis. In order to override potential redundancy in platelet functions, we also studied Hps3coa and control mice with moderate antibody-induced thrombocytopenia (10%) prior to infection. We found that sepsis-induced thrombocytopenia tended to be less severe in Hps3coa mice, and was significantly ameliorated in Hps3coa mice with low pre-infection platelet counts. Bacterial growth was similar in Hps3coa and control mice in the presence of normal platelet counts prior to infection, but lower in the lungs of Hps3coa mice with low pre-infection platelet counts. Hps3coa mice had unaltered lung pathology and distant organ injury during pneumosepsis, irrespective of pre-infection platelet counts; lung bleeding did not differ between Hps3coa and control mice. Clopidogrel did not influence any host response parameter. These data suggest that platelet ? granules can play a detrimental role in pneumosepsis by aggravating thrombocytopenia and impairing local antibacterial defense, but that these unfavorable effects only become apparent in the presence of low platelet counts.
| S-EPMC6738263 | biostudies-literature
Project description:Recently, we identified and characterized a novel protein, granuphilin, whose domain structure is similar to that of the Rab3 effector protein rabphilin3 (J. Wang, T. Takeuchi, H. Yokota, and T. Izumi, J. Biol. Chem. 274:28542-28548, 1999). Screening its possible Rab partner by a yeast two-hybrid system revealed that an amino-terminal zinc-finger domain of granuphilin interacts with Rab27a. Granuphilin preferentially bound to the GTP form of Rab27a. Formation of the Rab27a/granuphilin complex was readily detected in the pancreatic beta cell line MIN6. Moreover, the tissue distributions of Rab27a and granuphilin are remarkably similar: both had significant and specific expression in pancreatic islets and in pituitary tissue, but no expression was noted in the brain. Analyses by immunofluorescence, immunoelectron microscopy, and sucrose density gradient subcellular fractionation showed that Rab27a and granuphilin are localized on the membrane of insulin granules. These findings suggest that granuphilin functions as a Rab27a effector protein in beta cells. Overexpression of wild-type Rab27a and its GTPase-deficient mutant significantly enhanced high K(+)-induced insulin secretion without affecting basal insulin release. Although Rab3a, another exocytotic Rab protein, has some similarities with Rab27a in primary sequence, intracellular distribution, and affinity toward granuphilin, overexpression of Rab3a caused different effects on insulin secretion. These results indicate that Rab27a is involved in the regulated exocytosis of conventional dense-core granules possibly through the interaction with granuphilin, in addition to its recently identified role in lysosome-related organelles.
| S-EPMC135591 | biostudies-literature
Project description:Adrenal chromaffin cells release hormones and neuropeptides that are essential for physiological homeostasis. During this process, secretory granules fuse with the plasma membrane and deliver their cargo to the extracellular space. It was once believed that fusion was the final regulated step in exocytosis, resulting in uniform and total release of granule cargo. Recent evidence argues for nonuniform outcomes after fusion, in which cargo is released with variable kinetics and selectivity. The goal of this study was to identify factors that contribute to the different outcomes, with a focus on the Ca(2+)-sensing synaptotagmin (Syt) proteins. Two Syt isoforms are expressed in chromaffin cells: Syt-1 and Syt-7. We find that overexpressed and endogenous Syt isoforms are usually sorted to separate secretory granules and are differentially activated by depolarizing stimuli. In addition, overexpressed Syt-1 and Syt-7 impose distinct effects on fusion pore expansion and granule cargo release. Syt-7 pores usually fail to expand (or reseal), slowing the dispersal of lumenal cargo proteins and granule membrane proteins. On the other hand, Syt-1 diffuses from fusion sites and promotes the release of lumenal cargo proteins. These findings suggest one way in which chromaffin cells may regulate cargo release is via differential activation of synaptotagmin isoforms.
| S-EPMC4142614 | biostudies-literature
Project description:Granular platelet-sized polyphosphate nanoparticles (polyP NPs) were encapsulated in sterically stabilized liposomes, forming a potential, targeted procoagulant nanotherapy resembling human platelet dense granules in both structure and functionality. Dynamic light scattering (DLS) measurements reveal that artificial dense granules (ADGs) are colloidally stable and that the granular polyP NPs are encapsulated at high efficiencies. High-resolution scanning transmission electron microscopy (HR-STEM) indicates that the ADGs are monodisperse particles with a 150 nm diameter dense core consisting of P, Ca, and O surrounded by a corrugated 25 nm thick shell containing P, C, and O. Further, the ADGs manifest promising procoagulant activity: Detergent solubilization by Tween 20 or digestion of the lipid envelope by phospholipase C (PLC) allows for ADGs to trigger autoactivation of Factor XII (FXII), the first proteolytic step in the activation of the contact pathway of clotting. Moreover, ADGs' ability to reduce the clotting time of human plasma in the presence of PLC further demonstrate the feasibility to develop ADGs into a potential procoagulant nanomedicine.
| S-EPMC8767982 | biostudies-literature
Project description:BackgroundDevelopmental ontogeny of neonatal thrombopoiesis retains characteristics that are distinct from adults although molecular mechanisms remain unestablished.MethodsWe applied multiparameter quantitative platelet responses with integrated ribosome profiling/transcriptomic studies to better define gene/pathway perturbations regulating the neonatal-to-adult transition. A bioinformatics pipeline was developed to identify stable, neonatal-restricted platelet biomarkers for clinical application.ResultsCord blood (CB) platelets retained the capacity for linear agonist-receptor coupling linked to phosphatidylserine (PS) exposure and α-granule release, although a restricted block in cross-agonist activation pathways was evident. Functional immaturity of synergistic signaling pathways was due to younger ontogenetic age and singular underdevelopment of the protein secretory gene network, with reciprocal expansion of developmental pathways (E2F, G2M checkpoint, c-Myc) important for megakaryocytopoiesis. Genetic perturbations regulating vesicle transport and fusion (TOM1L1, VAMP3, SNAP23, and DNM1L) and PS exposure and procoagulant activity (CLCN3) were the most significant, providing a molecular explanation for globally attenuated responses. Integrated transcriptomic and ribosomal footprints identified highly abundant (ribosome-protected) DEFA3 (encoding human defensin neutrophil peptide 3) and HBG1 as stable biomarkers of neonatal thrombopoiesis. Studies comparing CB- or adult-derived megakaryocytopoiesis confirmed inducible and abundant DEFA3 antigenic expression in CB megakaryocytes, ~3.5-fold greater than in leukocytes (the most abundant source in humans). An initial feasibility cohort of at-risk pregnancies manifested by maternal/fetal hemorrhage (chimerism) were applied for detection and validation of platelet HBG1 and DEFA3 as neonatal thrombopoiesis markers, most consistent for HBG1, which displayed gestational age-dependent expression.ConclusionsThese studies establish an ontogenetically divergent stage of neonatal thrombopoiesis, and provide initial feasibility studies to track disordered fetal-to-adult megakaryocytopoiesis in vivo.
| S-EPMC10953828 | biostudies-literature
Project description:Understanding the underlying mechanisms of the well-established platelet hyporeactivity in neonates, would be of great relevance for both improving the clinical management of neonates, a population with a higher bleeding risk than adults (especially among sick and preterm infants), and getting new insights onto the regulatory mechanisms of platelet biology. Transcriptome analysis is a useful tool to identify mRNA signature affecting platelet function. However, human fetal/neonatal platelet transcriptome analysis has never been reported. Here, we used, for the first time, mRNA expression array to compare the platelet transcriptome changes during development. Microarray analysis was performed in pure platelet RNA obtained from adult and cord blood, using the same platform in two independent laboratories. A high correlation was obtained between arrays results for both adult and neonate platelet samples. There was also a good agreement between our adult results and those previously reported in three different studies. Gene enrichment analysis demonstrated that immunity- and platelet function-related genes are highly expressed in either developmental stage. Remarkably, 201 genes were found to be differentially expressed along development. In particular, neonatal platelets contain higher levels of mRNA that are associated with protein synthesis and processing, while they carry significantly lower levels of genes related with calcium transport/metabolism and cell signaling (including GNAZ). Overall, our results highlight that variations in platelet transcriptome may underline the hypo-functional phenotype of neonatal platelets, and further support the role of platelets in cellular immune response. A better characterization of the platelet transcriptome across development may help to elucidate the implications of transcriptome changes in different pathological conditions.
2017-02-03 | GSE94292 | GEO