scholarly journals Unraveling Secretory Mechanisms that Control Pentraxin 3 Secretion in Adipocytes During Inflammation

2021 ◽  
Vol 5 (Supplement_1) ◽  
pp. A60-A60
Author(s):  
Te-Yueh Lin ◽  
XiaoLi Chen
Keyword(s):  
Protein Secretion ◽  
Golgi Complex ◽  
Culture Media ◽  
Gradient Centrifugation ◽  
Brefeldin A ◽  
Pentraxin 3 ◽  
Metabolic Inflammation ◽  
Chemical Inhibitors ◽  
Carbonyl Cyanide ◽  
Mitochondrial Oxidation

Abstract As a soluble pattern recognition receptor, Pentraxin 3 (PTX3) plays an important role in innate immunity and obesity-associated metabolic inflammation. PTX3 is abundantly expressed and secreted in adipocytes in response to lipopolysaccharide (LPS) stimulation. Appropriate regulation of PTX3 secretion is critical for maintaining inflammatory homeostasis. This study aims to unravel the mechanisms that control PTX3 secretion in adipocytes during LPS-induced inflammation. Upon 6h treatment of LPS, PTX3 expression and secretion were significantly induced in 3T3-L1 and stromal-vascular (SV) differentiated adipocytes, but to a lesser extent in SV cells or 3T3-L1 fibroblasts. However, LPSdoes not significantly stimulate PTX3 expression and secretion in macrophages. Using chemical inhibitors of conventional and unconventional protein secretion, we explored the mechanisms for controlling LPS-stimulated PTX3 secretion. 3T3-L1 adipocytes were treated with LPS for 6h in the presence or absence of various inhibitors blocking protein secretion from the Golgi complex (Monensin and Brefeldin A), mitochondrial oxidation (carbonyl cyanide 3-chlorophenylhydrazone [CCCP]), autophagy-lysosome (chloroquine and 3-methyladenine) and inflammasome (Bay 11–7082 and wedelolactone) activation, or exosome synthesis and trafficking (GW4869, manumycin A, calpeptin, and Y-27632). There were no significant effects of all inhibitors except for Monensin, Brefeldin A, and CCCP on intracellular and secreted levels of PTX3 in adipocytes. We found that Monensin and Brefeldin A significantly blocked LPS-stimulated PTX3 secretion, resulting in cellular PTX3 accumulation in adipocytes. Disrupting mitochondrial membrane potential by CCCP caused the reduction in PTX3 secretion from adipocytes. Additionally, we detected PTX3 in exosomes isolated from LPS-treated adipocytes. Inhibiting exosome synthesis by Manumycin A attenuated LPS-stimulated PTX3 secretion in both adipocyte culture media and isolated exosomes but not in the non-exosomal fraction of media, suggesting the involvement of the exosomal pathway in PTX3 secretion. However, the levels of exosomal PTX3 were significantly lower than that of the non-exosomal PTX3, and only 4.3% of secreted PTX3 was detected in the exosomal fraction of cultural media. Inhibiting the Golgi complex pathway blocked both the exosomal and non-exosomal secretion of PTX3 in adipocytes. After further fractionation of isolated crude exosomes by the iodixanol density gradient centrifugation, we showed that the majority of PTX3 was found in the non-extracellular vesicular (EV) fractions; only a small portion of secreted PTX3 overlapped with the exosomal marker CD63 in the small EV fractions. We conclude that PTX3 is secreted mainly through the conventional protein secretion pathway and minimally through the exosomal or EV pathway in response to LPS stimulation.

scholarly journals Inhibition by brefeldin A of protein secretion from the apical cell surface of Madin-Darby canine kidney cells.

1991 ◽  
Vol 266 (27) ◽  
pp. 17729-17732 ◽  
Author(s):  
S.H. Low ◽  
S.H. Wong ◽  
B.L. Tang ◽  
P. Tan ◽  
V.N. Subramaniam ◽  
...  
Keyword(s):  
Cell Surface ◽  
Protein Secretion ◽  
Apical Cell ◽  
Brefeldin A ◽  
Kidney Cells ◽  
Madin Darby Canine Kidney ◽  
Darby Canine Kidney ◽  
Canine Kidney

scholarly journals Comparative biosynthesis, covalent post-translational modifications and efficiency of prosegment cleavage of the prohormone convertases PC1 and PC2: glycosylation, sulphation and identification of the intracellular site of prosegment cleavage of PC1 and PC2

1993 ◽  
Vol 294 (3) ◽  
pp. 735-743 ◽  
Author(s):  
S Benjannet ◽  
N Rondeau ◽  
L Paquet ◽  
A Boudreault ◽  
C Lazure ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Brefeldin A ◽  
Pulse Labelling ◽  
Prohormone Convertases ◽  
Post Translational Modifications ◽  
Intracellular Degradation ◽  
Golgi Compartment ◽  
Carbonyl Cyanide ◽  
Insulinoma Cells

We present herein the pulse-chase analysis of the biosynthesis of the prohormone convertases PC1 and PC2 in the endocrine GH4C1 cells infected with vaccinia virus recombinants expressing these convertases. Characterization of the pulse-labelled enzymes demonstrated that pro-PC1 (88 kDa) is cleaved into PC1 (83 kDa) and pro-PC2 (75 kDa) into PC2 (68 kDa). Secretion of glycosylated and sulphated PC1 (84 kDa) occurs about 30 min after the onset of biosynthesis, whereas glycosylated and sulphated PC2 (68 kDa) is detected in the medium after between 1 and 2 h. Furthermore, in the case of pro-PC2 only, we observed that a fraction of this precursor escapes glycosylation. A small proportion (about 5%) of the intracellular glycosylated pro-PC2 (75 kDa) is sulphated, and it is this glycosylated and sulphated precursor that is cleaved into the secretable 68 kDa form of PC2. Major differences in the carbohydrate structures of PC1 and PC2 are demonstrated by the resistance of the secreted PC1 to endoglycosidase H digestion and sensitivity of the secreted PC2 to this enzyme. Inhibition of N-glycosylation with tunicamycin caused a dramatic intracellular degradation of these convertases within the endoplasmic reticulum, with the net effect of a reduction in the available activity of PC1 and PC2. These results emphasize the importance of N-glycosylation in the folding and stability of PC1 and PC2. Pulse-labelling experiments in uninfected mouse beta TC3 and rat Rin m5F insulinoma cells, which endogenously synthesize PC2, showed that, as in infected GH4C1 cells, pro-PC2 predominates intracellularly. In order to define the site of prosegment cleavage, pulse-chase analysis was performed at low temperature (15 degrees C) or after treatment of GH4C1 cells with either brefeldin A or carbonyl cyanide m-chlorophenylhydrazone. These results demonstrated that the onset of the conversions of pro-PC1 into PC1 and non-glycosylated pro-PC2 into PC2 (65 kDa) occur in a pre-Golgi compartment, presumably within the endoplasmic reticulum. In contrast, pulse labelling in the presence of Na(2)35SO4 demonstrated that the processing of glycosylated and sulphated pro-PC2 occurs within the Golgi apparatus. In order to test the possibility that zymogen processing is performed by furin, we co-expressed this convertase with either pro-PC1 or pro-PC2. The data demonstrated the inability of furin to cleave either proenzyme.

scholarly journals Brefeldin A inhibits transport of the glycophorin-binding protein from Plasmodium falciparum into the host erythrocyte

1994 ◽  
Vol 300 (3) ◽  
pp. 821-826 ◽  
Author(s):  
J Benting ◽  
D Mattei ◽  
K Lingelbach
Keyword(s):  
Plasmodium Falciparum ◽  
Golgi Apparatus ◽  
Host Cell ◽  
Protein Secretion ◽  
Secretory Pathway ◽  
Binding Protein ◽  
Brefeldin A ◽  
Cell Cytoplasm ◽  
Parasite Cell ◽  
Host Cell Cytoplasm

Plasmodium falciparum, a protozoan parasite of the human erythrocyte, causes the most severe form of malaria. During its intraerythrocytic development, the parasite synthesizes proteins which are exported into the host cell. The compartments involved in the secretory pathway of P. falciparum are still poorly characterized. A Golgi apparatus has not been identified, owing to the lack of specific protein markers and Golgi-specific post-translational modifications in the parasite. The fungal metabolite brefeldin A (BFA) is known to inhibit protein secretion in higher eukaryotes by disrupting the integrity of the Golgi apparatus. We have used the parasite-encoded glycophorin-binding protein (GBP), a soluble protein found in the host cell cytoplasm, as a marker to investigate the effects of BFA on protein secretion in the intracellular parasite. In the presence of BFA, GBP was not transported into the erythrocyte, but remained inside the parasite cell. The effect caused by BFA was reversible, and the protein could be chased into the host cell cytoplasm within 30 min. Transport of GBP from the BFA-sensitive site into the host cell did not require protein synthesis. Similar observations were made when infected erythrocytes were incubated at 15 degrees C. Incubation at 20 degrees C resulted in a reduction rather than a complete block of protein export. The relevance of our findings to the identification of compartments involved in protein secretion from the parasite cell is discussed.

scholarly journals RAB6 and microtubules restrict protein secretion to focal adhesions

2019 ◽  
Vol 218 (7) ◽  
pp. 2215-2231 ◽  
Author(s):  
Lou Fourriere ◽  
Amal Kasri ◽  
Nelly Gareil ◽  
Sabine Bardin ◽  
Hugo Bousquet ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Cell Surface ◽  
Protein Secretion ◽  
Golgi Complex ◽  
Essential Role ◽  
Focal Adhesions ◽  
Secreted Proteins ◽  
Cell Compartments ◽  
Secretion Assay

To ensure their homeostasis and sustain differentiated functions, cells continuously transport diverse cargos to various cell compartments and in particular to the cell surface. Secreted proteins are transported along intracellular routes from the endoplasmic reticulum through the Golgi complex before reaching the plasma membrane along microtubule tracks. Using a synchronized secretion assay, we report here that exocytosis does not occur randomly at the cell surface but on localized hotspots juxtaposed to focal adhesions. Although microtubules are involved, the RAB6-dependent machinery plays an essential role. We observed that, irrespective of the transported cargos, most post-Golgi carriers are positive for RAB6 and that its inactivation leads to a broad reduction of protein secretion. RAB6 may thus be a general regulator of post-Golgi secretion.

scholarly journals Influenza virus hemagglutinin trimers and monomers maintain distinct biochemical modifications and intracellular distribution in brefeldin A-treated cells.

1991 ◽  
Vol 2 (7) ◽  
pp. 549-563 ◽  
Author(s):  
G Russ ◽  
J R Bennink ◽  
T Bächi ◽  
J W Yewdell
Keyword(s):  
Endoplasmic Reticulum ◽  
Influenza Virus ◽  
Monoclonal Antibodies ◽  
Golgi Complex ◽  
Brefeldin A ◽  
Retrograde Transport ◽  
Cell Fractionation ◽  
Influenza Virus Hemagglutinin ◽  
Infected Cells ◽  
Vesicular Compartment

Brefeldin A (BFA) induces the retrograde transport of proteins from the Golgi complex (GC) to the endoplasmic reticulum (ER). It is uncertain, however, whether the drug completely merges the ER with post-ER compartments, or whether some of their elements remain physically and functionally distinct. We investigated this question by the use of monoclonal antibodies specific for monomers and trimers of the influenza virus hemagglutinin (HA). In untreated influenza virus-infected cells, monomers and trimers almost exclusively partition into the ER and GC, respectively. In BFA-treated cells, both monomers and trimers are detected in the ER by immunofluorescence. Cell fractionation experiments indicate, however, that whereas HA monomers synthesized in the presence of BFA reside predominantly in vesicles with a characteristic density of the ER, HA trimers are primarily located in lighter vesicles characteristic of post-ER compartments. Biochemical experiments confirm that in BFA-treated cells, trimers are more extensively modified than monomers by GC-associated enzymes. Additional immunofluorescence experiments reveal that in BFA-treated cells, HA monomers can exist in an ER subcompartment less accessible to trimers and, conversely, that trimers are present in a vesicular compartment less accessible to monomers. These findings favor the existence of a post-ER compartment for which communication with the ER is maintained in the presence of BFA and suggest that trimers cycle between this compartment and the ER, but have access to only a portion of the ER.

87 EVALUATION OF THE NUMERICAL CHROMOSOMAL ABNORMALITIES ON IN VITRO EARLY BOVINE EMBRYOS: EFFECT OF THE CELL CO-CULTURE WITH GRANULOSA CELLS

2014 ◽  
Vol 26 (1) ◽  
pp. 157
Author(s):  
S. Demyda-Peyrás ◽  
M. Hidalgo ◽  
J. Dorado ◽  
M. Moreno-Millan
Keyword(s):  
Embryo Development ◽  
Granulosa Cells ◽  
Chromosomal Abnormalities ◽  
Culture Media ◽  
Gradient Centrifugation ◽  
Early Embryo ◽  
Bovine Embryos ◽  
Humid Atmosphere ◽  
Early Embryos

Chromosomal numerical abnormalities (CNA) were described as a major cause of developmental failures in in vitro-produced (IVP) embryos. It has been described that CNA are influenced by the post-fertilization culture environment of the embryo. Furthermore, it was demonstrated that the use of different culture media affects the CNA rates. The addition of granulosa cells during early embryo development is a well-known procedure to simplify the culture of bovine IVP and cloned embryos. This technique avoids the use of culture environments saturated with N2 (tri-gas chambers). The aim of this study was to determine the effect of the addition of granulosa cells in the chromosomal abnormalities of IVP cattle embryos. Cumulus–oocyte complexes (COC) were matured in TCM-199 medium, supplemented with glutamine, sodium pyruvate, FSH, LH, oestradiol, and gentamicin during 20 h at 38.5°C in a 5% CO2 humid atmosphere. Subsequently, matured oocytes were fertilized in IVF-TALP medium using 1 × 106 spermatozoa mL–1, selected through a Percoll gradient centrifugation. After fertilization, zygotes were divided in 2 groups and cultured in TCM-199 medium for 48 h, with (TCM-GC) or without (TCM) the addition of 1 × 106 granulosa cells. These cells were obtained by centrifuging and washing the follicular fluid remaining from searching dishes and adjusted to the working concentration. After culture, a total of 106 early embryos (72 hpi) were cytogenetically evaluated following our standard laboratory techniques. Embryos showing normal development were individually fixed onto a slide, disaggregated into blastomeres with acetic acid, and stained with Giemsa solution. Chromosomal numerical abnormalities were evaluated by direct observation at 1250× magnification in a brightfield microscope. Percentage of normal diploid embryos (D) and abnormal haploid (H), polyploid (P), or aneuploid (A) embryos were determined. Results were statistically compared between treatments using a Z test for proportions. Results were: D = 81.4%, H = 7.2%, P = 7.2%. and A = 3.6% in TCM and D = 84.3%, H = 3.9%, P = 9.8%, and A = 1.9% in TCM-GC. No significant differences (P > 0.05) were found between culture media in the chromosomal abnormality rates. According to our results, the use of somatic cells in co-culture during embryo development did not influence the appearance of abnormal complements in the produced embryos. This would allow the use of GC as a potential complement to simplify the techniques used in the culture of bovine embryos until Day 3.

scholarly journals Isolation and characterization of monoclonal antibodies directed against plant plasma membrane and cell wall epitopes: identification of a monoclonal antibody that recognizes extensin and analysis of the process of epitope biosynthesis in plant tissues and cell cultures.

1988 ◽  
Vol 107 (1) ◽  
pp. 163-175 ◽  
Author(s):  
D J Meyer ◽  
C L Afonso ◽  
D W Galbraith
Keyword(s):  
Monoclonal Antibody ◽  
Cell Wall ◽  
Monoclonal Antibodies ◽  
Plasma Membrane ◽  
Solid Phase ◽  
Culture Media ◽  
Gradient Centrifugation ◽  
Cell Suspension Cultures ◽  
Isolation And Characterization

Membranes from tobacco cell suspension cultures were used as antigens for the preparation of monoclonal antibodies. Use of solid phase and indirect immunofluorescence assays led to the identification of hybridomas producing antibodies directed against cell surface epitopes. One of these monoclonal antibodies (11.D2) was found to recognize a molecular species which on two-dimensional analysis (using nonequilibrium pH-gradient electrophoresis and SDS-PAGE) was found to have a high and polydisperse molecular mass and a very basic isoelectric point. This component was conspicuously labeled by [3H]proline in vivo. The monoclonal antibody cross-reacted with authentic tomato extensin, but not with potato lectin nor larch arabinogalactan. Use of the monoclonal antibody as an immunoaffinity reagent allowed the purification of a tobacco glycoprotein which was identical in amino acid composition to extensin. Finally, immunocytological analyses revealed tissue-specific patterns of labeling by the monoclonal antibody that were identical to those observed with a polyclonal antibody raised against purified extensin. We have concluded that monoclonal antibody 11.D2 recognizes an epitope that is carried exclusively by extensin. Analysis of cellular homogenates through differential and isopycnic gradient centrifugation revealed that biosynthesis of the extensin epitope was found on or within the membranes of the endoplasmic reticulum, Golgi region and plasma membrane. This result is consistent with the progressive glycosylation of the newly-synthesized extensin polypeptide during its passage through a typical eukaryotic endomembrane pathway of secretion. The 11.D2 epitope was not found in protoplasts freshly isolated from leaf tissues. However, on incubation of these protoplasts in appropriate culture media, biosynthesis of the epitope was initiated. This process was not impeded by the presence of chemicals that are reported to be inhibitors of cell wall production or of proline hydroxylation.

scholarly journals An AlphaScreen Assay for the Discovery of Synthetic Chemical Inhibitors of Glucagon Production

2015 ◽  
Vol 21 (4) ◽  
pp. 325-332 ◽  
Author(s):  
Matthew R. Evans ◽  
Shuguang Wei ◽  
Bruce A. Posner ◽  
Roger H. Unger ◽  
Michael G. Roth
Keyword(s):  
Cell Culture ◽  
Small Molecules ◽  
Culture Media ◽  
Glucagon Secretion ◽  
Cell Culture Media ◽  
Glucagon Receptor ◽  
Synthetic Compounds ◽  
Glucose Levels ◽  
Blood Glucose Levels ◽  
Chemical Inhibitors

Glucose homeostasis is primarily controlled by two opposing hormones, insulin and glucagon, and diabetes results when insulin fails to inhibit glucagon action. Recent efforts to control glucagon in diabetes have focused on antagonizing the glucagon receptor, which is effective in lowering blood glucose levels but leads to hyperglucogonemia in rodents. An alternative strategy would be to control glucagon production with small molecules. In pursuit of this goal, we developed a homogeneous AlphaScreen assay for measuring glucagon in cell culture media and used this in a high-throughput screen to discover synthetic compounds that inhibited glucagon secretion from an alpha cell–like cell line. Some of these compounds inhibited transcription of the glucagon gene.

scholarly journals Sphingomyelin-enriched Microdomains at the Golgi Complex

2001 ◽  
Vol 12 (6) ◽  
pp. 1819-1833 ◽  
Author(s):  
Ioannis Gkantiragas ◽  
Britta Brügger ◽  
Ernstpeter Stüven ◽  
Dora Kaloyanova ◽  
Xue-Yi Li ◽  
...  
Keyword(s):  
Golgi Complex ◽  
Protein Interactions ◽  
Dynamic Equilibrium ◽  
Buoyant Density ◽  
Brefeldin A ◽  
Vacuolar Atpase ◽  
Morphological Data ◽  
Temperature Sensitive ◽  
Cell Extracts ◽  
The Stability

Sphingomyelin- and cholesterol-enriched microdomains can be isolated as detergent-resistant membranes from total cell extracts (total-DRM). It is generally believed that this total-DRM represents microdomains of the plasma membrane. Here we describe the purification and detailed characterization of microdomains from Golgi membranes. These Golgi-derived detergent-insoluble complexes (GICs) have a low buoyant density and are highly enriched in lipids, containing 25% of total Golgi phospholipids including 67% of Golgi-derived sphingomyelin, and 43% of Golgi-derived cholesterol. In contrast to total-DRM, GICs contain only 10 major proteins, present in nearly stoichiometric amounts, including the α- and β-subunits of heterotrimeric G proteins, flotillin-1, caveolin, and subunits of the vacuolar ATPase. Morphological data show a brefeldin A-sensitive and temperature-sensitive localization to the Golgi complex. Strikingly, the stability of GICs does not depend on its membrane environment, because, after addition of brefeldin A to cells, GICs can be isolated from a fused Golgi-endoplasmic reticulum organelle. This indicates that GIC microdomains are not in a dynamic equilibrium with neighboring membrane proteins and lipids. After disruption of the microdomains by cholesterol extraction with cyclodextrin, a subcomplex of several GIC proteins including the B-subunit of the vacuolar ATPase, flotillin-1, caveolin, and p17 could still be isolated by immunoprecipitation. This indicates that several of the identified GIC proteins localize to the same microdomains and that the microdomain scaffold is not required for protein interactions between these GIC proteins but instead might modulate their affinity.

Kunitz 3-Selective but Not Kunitz 2-Selective TFPI Inhibitors Cause Release of Tfpiα from Endothelial Cells: Insights into the Release Mechanism

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 2558-2558
Author(s):  
Julie A. Peterson ◽  
Cecilia Augustsson ◽  
Susan A Maroney ◽  
Helle Heibroch Petersen ◽  
Ida Hilden ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Endothelial Cells ◽  
Cell Surface ◽  
Culture Media ◽  
Brefeldin A ◽  
Release Mechanism ◽  
Human Endothelial Cells ◽  
Intracellular Pool ◽  
The Media ◽  
Ea.Hy926 Cells

Abstract BACKGROUND: Tissue factor pathway inhibitor (TFPI) is an anticoagulant protein that regulates early blood coagulation events and contains 3 Kunitz-type serine protease domains (K1-3). TFPI inhibitors are being developed to treat hemophilia. However, an inhibitory aptamer to the K3 domain of TFPI has been found to produce an increase in plasma TFPI with associated bleeding. Therefore, understanding the mechanisms causing release of TFPI from endothelium is important for further development of these drugs. Two major isoforms of TFPI, TFPIα and TFPIβ, are generated by human endothelial cells. Both isoforms contain K1 and K2. TFPIβ attaches to the cell surface via a C-terminal glycosylphosphatidyl inositol (GPI) anchor. TFPIα is a soluble protein with an additional Kunitz domain (K3) and a basic C-terminal tail present in human plasma. It has been found that plasma TFPIα promptly increases 2- to 4-fold following heparin infusion. Treatment of cultured human endothelial cells with heparin also promptly increases TFPIα 2- to 4-fold in culture media, suggesting that the basic C-terminal tail of TFPIα interacts with cell surface glycosaminoglycans (GAGs) and that this association is disrupted by heparin, releasing TFPIα into plasma or media. However, cell surface TFPI can be almost entirely removed by treatment with phosphatidylinositol phospholipase C, an enzyme that removes GPI-anchored proteins from the cell surface, indicating that only the GPI-anchored TFPIβ is present at the surface. This suggests that heparin may cause release of TFPIα from an intracellular pool. Thus, the mechanism of heparin-induced TFPIα release from endothelium remains unresolved. METHODS: Wild type (WT) and aerolysin-resistant (AR) Ea.hy926 cells, which lack GPI-anchored proteins, including TFPIβ, but produce normal amounts of TFPIα, were used to examine how heparin and anti-TFPI antibodies induce release of TFPI. For this, WT or AR cells were incubated for 15 minutes at room temperature or 4°C, with either heparin, 0.3 M NaCl, anti-K2 or anti-K3 antibody. Surface TFPI was detected with an anti-K2 antibody using flow cytometry. TFPIα released into culture media was measured with a TFPIα-specific ELISA. Brefeldin A, an inhibitor of protein transport from endoplasmic reticulum to Golgi, was used to block TFPIα secretion. Real time PCR was used to measure changes in TFPI mRNA. RESULTS: WT cells express surface TFPI that can be detected with an anti-K2 antibody using flow cytometry and which is not altered by exposure of cells to heparin or anti-K3 antibody. AR cells do not have TFPI on their surface that is detectable by flow cytometry. Incubation of WT or AR cells with heparin, 0.3 M NaCl, or anti-K3 antibody produced an approximately 4-fold increase of TFPIα released into culture media. This was not observed when cells were incubated with anti-K2 antibody. To determine if heparin induces release of TFPIα from inside the cell, they were incubated for 15 minutes with heparin 4 times, in the presence or absence of Brefeldin A. During the fourth 15 minute treatment the amount of TFPIα secreted into the media was equal in heparin-treated or control cells. The cells were then allowed to incubate for an additional hour in the presence or absence of heparin. During this time, heparin-treated cells secreted TFPIα at a 2-fold faster rate than cells in buffer only (p=0.036). This difference was not observed in cells treated with Brefeldin A, which reduced TFPIα secretion by almost 5-fold (p=0.005). TFPIα transcript levels were not different between the heparin- and non-heparin-treated cells. CONCLUSION: TFPIα is released from Ea.hy926 cells by heparin and an anti-K3 antibody, both of which bind to the C-terminal region of TFPIα, while an anti-K2 antibody has been shown not to cause release of TFPIα from the cells. Indirect evidence suggests that there is a pool of TFPIα associated with cell surface GAGs and that this pool is released by agents that disrupt this interaction. However, the presence of TFPIα on the cell surface cannot be directly demonstrated using flow cytometry. Cells stripped of heparin-releasable TFPIα continue to secrete it into the media at a faster rate in the presence of heparin. Heparin does not alter transcription of TFPIα. Instead, it appears to enhance its secretion, perhaps by diverting it from storage in an intracellular pool. Disclosures Augustsson: Novo Nordisk: Employment. Heibroch Petersen:Novo Nordisk: Employment. Hilden:Novo Nordisk: Employment. Mast:Novo Nordisk: Research Funding; Siemens: Honoraria.

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