Platelet secretion and hemostasis require syntaxin-binding protein STXBP5

Ye, Shaojing; Huang, Yunjie; Joshi, Smita; Zhang, Jinchao; Yang, Fanmuyi; Zhang, Guoying; Smyth, Susan S.; Li, Zhenyu; Takai, Yoshimi; Whiteheart, Sidney W.

doi:10.1172/jci75572

Cited by 56 publications

(56 citation statements)

References 59 publications

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“…Genotyping was performed by PCR using DNA prepared from tail biopsies (Sakisaka et al., 2008); wild‐type littermates were used as controls. These STXBP5/Tom −/− mice were shown to be lacking tomosyn‐1, but none of the other elements of the secretory machinery by quantitative western blotting of different tissues (Sakisaka et al., 2008; Ye et al., 2014). For the kindling progression data, 14 Tom +/+ and 15 Tom −/− mice were used.…”

Section: Methodsmentioning

confidence: 99%

Linking kindling to increased glutamate release in the dentate gyrus of the hippocampus through the STXBP5/tomosyn‐1 gene

et al. 2017

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IntroductionIn kindling, repeated electrical stimulation of certain brain areas causes progressive and permanent intensification of epileptiform activity resulting in generalized seizures. We focused on the role(s) of glutamate and a negative regulator of glutamate release, STXBP5/tomosyn‐1, in kindling.MethodsStimulating electrodes were implanted in the amygdala and progression to two successive Racine stage 5 seizures was measured in wild‐type and STXBP5/tomosyn‐1−/− (Tom−/−) animals. Glutamate release measurements were performed in distinct brain regions using a glutamate‐selective microelectrode array (MEA).ResultsNaïve Tom−/− mice had significant increases in KCl‐evoked glutamate release compared to naïve wild type as measured by MEA of presynaptic release in the hippocampal dentate gyrus (DG). Kindling progression was considerably accelerated in Tom−/− mice, requiring fewer stimuli to reach a fully kindled state. Following full kindling, MEA measurements of both kindled Tom+/+ and Tom−/− mice showed significant increases in KCl‐evoked and spontaneous glutamate release in the DG, indicating a correlation with the fully kindled state independent of genotype. Resting glutamate levels in all hippocampal subregions were significantly lower in the kindled Tom−/− mice, suggesting possible changes in basal control of glutamate circuitry in the kindled Tom−/− mice.ConclusionsOur studies demonstrate that increased glutamate release in the hippocampal DG correlates with acceleration of the kindling process. Although STXBP5/tomosyn‐1 loss increased evoked glutamate release in naïve animals contributing to their prokindling phenotype, the kindling process can override any attenuating effect of STXBP5/tomosyn‐1. Loss of this “braking” effect of STXBP5/tomosyn‐1 on kindling progression may set in motion an alternative but ultimately equally ineffective compensatory response, detected here as reduced basal glutamate release.

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Section: Methodsmentioning

confidence: 99%

Linking kindling to increased glutamate release in the dentate gyrus of the hippocampus through the STXBP5/tomosyn‐1 gene

et al. 2017

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“…To test this hypothesis, we analyzed the sialylation status of IgG molecules from Tomosyn-1 −/− animals, which have normal platelet numbers but an approximately 40% decrease in α-granule release upon activation (26). We found that the Tomosyn-1 −/− mice had a concomitant 40% decrease in the percentage of sialylated IgG molecules (Fig.…”

Section: Platelets At Least Partially Supply the Nucleotide Sugar Donormentioning

confidence: 98%

B-cell–independent sialylation of IgG

Jones

Oswald

Joshi

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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IgG carrying terminal α2,6-linked sialic acids added to conserved N-glycans within the Fc domain by the sialyltransferase ST6Gal1 accounts for the anti-inflammatory effects of large-dose i.v. Ig (IVIg) in autoimmunity. Here, B-cell-specific ablation of ST6Gal1 in mice revealed that IgG sialylation can occur in the extracellular environment of the bloodstream independently of the B-cell secretory pathway. We also discovered that secreted ST6Gal1 is produced by cells lining central veins in the liver and that IgG sialylation is powered by serum-localized nucleotide sugar donor CMP-sialic acid that is at least partially derived from degranulating platelets. Thus, antibody-secreting cells do not exclusively control the sialylationdependent anti-inflammatory function of IgG. Rather, IgG sialylation can be regulated by the liver and platelets through the corresponding release of enzyme and sugar donor into the cardiovascular circulation.W hile en route to the plasma membrane as integral membrane proteins or for secretion, glycoproteins exiting the endoplasmic reticulum traverse the cis-, medial-, and trans-Golgi apparatus where the associated N-linked glycans are remodeled into their final form. This classically defined secretory pathway dictates that the glycoform of all glycoproteins produced by a cell is largely determined by the cohort of enzymes within the Golgi and the metabolic circumstances of that specific cell.Protein glycosylation is known to play fundamental roles in all aspects of biology, but has recently gained significant attention in immunology. When administered at high doses, i.v. Ig (IVIg) is an effective anti-inflammatory treatment for autoimmune patients (1). In 2006, it was discovered that the ∼10% of IgG molecules that carry α2,6-linked sialic acids upon the conserved biantennary N-glycans within the Fc domain provided the potent IVIg anti-inflammatory activity in autoimmune disease (2). Indeed, enrichment for the sialylated IgG (sIgG) fraction from IVIg pools increased the efficacy of treatment in mouse models of arthritis 100-fold in an IL-4-dependent fashion through receptors such as CD209 (DC-SIGN) (3, 4). Moreover, it was reported that sialylation of IgG also impacts antibody affinity maturation, although the mechanism underlying this phenomenon remains to be fully elucidated (5). These data indicate that sialylation serves as the mechanism underlying pleotropic IgG function (3,4,6).Epidemiologic analyses published since the reports cited above are consistent with this model. For example, female rheumatoid arthritis patients often go into remission during pregnancy and then relapse following childbirth. Analysis of sIgG levels before, during, and after pregnancy showed that the level of sIgG increases rapidly during pregnancy-induced remission, whereas during periods of exacerbated disease, sIgG is essentially undetectable (7,8). To date, it is unclear whether IgG sialylation patterns precede or result from the inflammatory state, and essentially nothing is known about the regulatory mecha...

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“…The mixture was analyzed by fluorescence-activated cell sorter (FACS) as described. 2 To measure FITC-Fg binding, platelets (5.0 3 10 8 /mL) were incubated, on ice, with 0.06 or 0.12 mg/mL FITC-Fg for 20 minutes. Platelets were fixed with 2% paraformaldehyde and analyzed by FACS.…”

Section: Flow Cytometry Analysismentioning

confidence: 99%

“…Platelet adhesion and spreading were performed as described by Ye et al 2 and detailed in the supplemental Materials and Methods. Briefly, for platelet adhesion, calcein labeled platelets were seeded onto Fg-or bovine serum albumin (BSA)-coated plates for 30 minutes at 37°C.…”

Section: Static Platelet Adhesion and Platelet Spreadingmentioning

confidence: 99%

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Arf6 controls platelet spreading and clot retraction via integrin αIIbβ3 trafficking

Huang¹,

Joshi²,

Xiang

et al. 2016

Blood

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• Arf6 selectively regulates endocytic trafficking of platelet a IIb b 3 .• Endocytosis contributes to acute platelet function.Platelet and megakaryocyte endocytosis is important for loading certain granule cargo (ie, fibrinogen [Fg] and vascular endothelial growth factor); however, the mechanisms of platelet endocytosis and its functional acute effects are understudied. Adenosine 5'-diphosphate-ribosylation factor 6 (Arf6) is a small guanosine triphosphate-binding protein that regulates endocytic trafficking, especially of integrins. To study platelet endocytosis, we generated platelet-specific Arf6 knockout (KO) mice. Arf6 KO platelets had less associated Fg suggesting that Arf6 affects a IIb b 3 -mediated Fg uptake and/or storage. Other cargo was unaffected. To measure Fg uptake, mice were injected with biotinylated-or fluorescein isothiocyanate (FITC)-labeled Fg. Platelets from the injected Arf6 KO mice showed lower accumulation of tagged Fg, suggesting an uptake defect. Ex vivo, Arf6 KO platelets were also defective in FITC-Fg uptake and storage. Immunofluorescence analysis showed initial trafficking of FITC-Fg to a Rab4-positive compartment followed by colocalization with Rab11-positive structures, suggesting that platelets contain and use both early and recycling endosomes. Resting and activated a IIb b 3 levels, as measured by flow cytometry, were unchanged; yet, Arf6 KO platelets exhibited enhanced spreading on Fg and faster clot retraction. This was not the result of alterations in a IIb b 3 signaling, because myosin light-chain phosphorylation and Rac1/RhoA activation were unaffected. Consistent with the enhanced clot retraction and spreading, Arf6 KO mice showed no deficits in tail bleeding or FeCl 3 -induced carotid injury assays. Our studies present the first mouse model for defining the functions of platelet endocytosis and suggest that altered integrin trafficking may affect the efficacy of platelet function. (Blood. 2016;127(11):1459-1467 IntroductionIt is increasingly clear that platelets are capable of different types of intracellular membrane trafficking. Platelet exocytosis and autophagy are critical for hemostasis. [1][2][3][4] Platelet endocytosis is important for granule cargo loading. Platelets selectively take up certain cargo (ie, fibrinogen [Fg] and vascular endothelial growth factor) from plasma and package it into a-granules. [5][6][7][8] However, the molecular mechanisms of platelet endocytosis are largely unknown. It is also unclear whether platelet endocytosis contributes to acute platelet functions beyond granule cargo loading. The goal of this study is to begin to address these fundamental questions.The Ras-like, small guanosine triphosphate (GTP)-binding proteins called adenosine 5'-diphosphate-ribosylation factors (Arf's), are key intracellular trafficking regulators. They cycle between inactive guanosine diphosphate (GDP)-bound and active GTP-bound states and are important for multiple functions (eg, actin cytoskeleton remodeling, lipid metabolism, and vesicle traffickin...

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Platelet secretion and hemostasis require syntaxin-binding protein STXBP5

Cited by 56 publications

References 59 publications

Linking kindling to increased glutamate release in the dentate gyrus of the hippocampus through the STXBP5/tomosyn‐1 gene

Linking kindling to increased glutamate release in the dentate gyrus of the hippocampus through the STXBP5/tomosyn‐1 gene

B-cell–independent sialylation of IgG

Arf6 controls platelet spreading and clot retraction via integrin αIIbβ3 trafficking

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