Molten globule monomer to condensed dimer: role of disulfide bonds in platelet factor-4 folding and subunit association

Biochemistry ◽  
1992 ◽  
Vol 31 (48) ◽  
pp. 12255-12265 ◽  
Author(s):  
Kevin H. Mayo ◽  
Sharon Barker ◽  
Michael J. Kuranda ◽  
Anthony J. Hunt ◽  
Jill A. Myers ◽  
...  
Keyword(s):  
Disulfide Bonds ◽  
Molten Globule ◽  
Platelet Factor 4 ◽  
Platelet Factor

scholarly journals The Role of Platelet Factor 4 in Local and Remote Tissue Damage in a Mouse Model of Mesenteric Ischemia/Reperfusion Injury

PLoS ONE ◽  
2012 ◽  
Vol 7 (7) ◽  
pp. e39934 ◽  
Author(s):  
Peter H. Lapchak ◽  
Antonis Ioannou ◽  
Poonam Rani ◽  
Linda A. Lieberman ◽  
Kazuhisa Yoshiya ◽  
...  
Keyword(s):  
Mouse Model ◽  
Reperfusion Injury ◽  
Tissue Damage ◽  
Mesenteric Ischemia ◽  
Ischemia Reperfusion Injury ◽  
Ischemia Reperfusion ◽  
Platelet Factor 4 ◽  
Platelet Factor

The role of platelet factor 4 in platelet aggregation induced by the antibodies implicated in heparin-induced thrombocytopenia

2001 ◽  
Vol 12 (7) ◽  
pp. 511-520 ◽  
Author(s):  
G. T. Gerotziafas ◽  
I. Elalamy ◽  
C. Lecrubier ◽  
J. Lebrazi ◽  
M. Mirshahi ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Platelet Factor 4 ◽  
Platelet Factor ◽  
Heparin Induced Thrombocytopenia

scholarly journals Conditional Knockout of LRP1 in Murine Megakaryocytes and Its Affects on Platelet Factor 4 Biology in Megakaryocytes

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 4150-4150
Author(s):  
Michele P Lambert ◽  
Liqing Xiao ◽  
Mortimer Poncz
Keyword(s):  
Bone Marrow ◽  
Platelet Count ◽  
Steady State ◽  
Platelet Factor 4 ◽  
Conditional Knockout ◽  
Platelet Factor ◽  
Paracrine Effects ◽  
Animal Survival ◽  
Count Recovery

Abstract We have previously shown that platelet factor 4 (PF4, CXCL4), which is synthesized almost exclusively by megakaryocytes undergoes release intramedullary after which it can undergo reuptake into alpha-granules, but also can be an important negative paracrine regulator of megakaryopoiesis, effecting platelet recovery post-radiation or chemotherapy. Animals that express high levels of human (h) PF4 in addition to their normal levels of murine (m) PF4 (hPF4+) have increased sensitivity to radiation- and chemotherapy-induced thrombocytopenia when compared to wild type (WT) mice or to mice that lack endogenous PF4 (mPF4-/-). Both PF4 reuptake and the negative paracrine effects are at least partially dependent upon the presence of low-density lipoprotein receptor related protein-1 (LRP1) on the surface of megakaryocytes as shown using shRNA suppression of megakaryocyte LRP1 levels. To further understand the role of LRP1 in megakaryopoiesis, we studied LRP1 expressed on primary megakaryocytes in murine models. Homozygous knockout for LRP1 constitutively is embryonically lethal and heterozygous deficiency of LRP1 is insufficient to have an observed effect on PF4 biology. We now established a megakaryocyte-specific knockout of LRP1 using a floxed LRP1 mouse previously described by Rohlman et al, mated to the Cre- PF4 promotor-driven Cre recombinase (Cre+) mice previously described by Tiedt et al. Megakaryocytes from mice that were LRP1fl/fl/Cre+ had no detectable LRP1 mRNA or LRP1 surface protein expression by flow cytometry, while LRP1fl/fl/Cre- mice were essentially identical to WT mice. Baseline platelet counts in LRP1fl/fl/Cre+ and LRP1fl/fl/Cre- mice did not different from each other, and there was no difference in bone marrow derived megakaryocyte ploidy. PF4 available in platelet releasate of LRP1fl/fl/Cre+ platelets was also significantly less than in LRP1fl/fl/Cre- platelets (208 ± 42 vs. 362 ± 47 IU/106 platelets, p=0.002) consistent with a role of LRP1 in PF4 reuptake into megakaryocytes in the steady-state and demonstrating that >42% of PF4 may be released during PF4 megakaryopoiesis and requires megakaryocyte LRP1 expression. In siru cultured LRP1fl/fl/Cre+ megakaryocytes exposed to exogenous hPF4 has a lower level of total PF4 levels than LRP1fl/fl/Cre- megakaryocytes (191 ± 7 vs. 236 ± 17 IU/106 cells, respectively (p=0.03)). A similar effect was seen in liquid bone marrow culture assays. Finally, while LRP1fl/fl/Cre+/hPF4+ mice had similar platelet count recovery after irradiation compared to LRP1fl/fl/Cre+/WT mice, treatment of these mice with a heparin-derivative (ODSH) shown to significantly improve platelet count recovery and animal survival in both WT and hPF4+ mice had no effect on either platelet count recovery or animal survival in animals that were also LRP1fl/fl/Cre+. These data demonstrate that nearly half of the total PF4 in megakaryocytes undergoes recycling in vivo and that LRP1 is important for this phenomenon in the steady-state. LRP1 is also important in the negative paracrine effect of PF4 in stress megakaryopoiesis though LRP1 may affect megakaryocyte biology by non-PF4-dependent pathways as well. Whether the two observations – PF4 uptake and negative paracrine effects – are mechanistically related or are distinct LRP1-dependent pathways now needs to be elucidated. Disclosures Xiao: ECRI Institute: Employment.

scholarly journals Role of kidney in the catabolic clearance of human platelet antiheparin proteins from rat circulation

Blood ◽  
1981 ◽  
Vol 57 (2) ◽  
pp. 233-238
Author(s):  
CP Bastl ◽  
J Musial ◽  
M Kloczewiak ◽  
J Guzzo ◽  
I Berman ◽  
...  
Keyword(s):  
Renal Excretion ◽  
Kidney Tissue ◽  
Rat Plasma ◽  
Renal Tissue ◽  
Human Platelets ◽  
Platelet Factor 4 ◽  
Metabolic Clearance ◽  
Platelet Factor ◽  
Functioning Kidney

Stimulated platelets release at least two antiheparin proteins: platelet factor 4 (PF4) and low affinity platelet factor 4 (LA-PF4) from which beta-thromboglobulin (beta TG) is derived. We have found previously marked elevation of LA-PF4/beta TG antigen in platelet poor plasma of patients with chronic renal failure, whereas levels of PF4 remained normal. Therefore, we examined the role of the kidneys in the metabolic clearance of LA-PF4/beta TG and PF4. The supernates of aggregates of thrombin-stimulated human platelets were injected into sham operated control rats, nephrectomized rats, and into rats with acute ureteral ligation. The disappearance of human LA-PF4/beta TG antigen and PF4 in rat plasma determined by specific radioimmunoassays followed biphasic exponential curves. The half-lives (t1/2) for the fast and slow components of LA-PF4 in control rats were 6.4 and 68.4 min. Nephrectomy significantly increased these times to 9.7 and 144 min, while ureteral ligation resulted in no significant change. Comparison of the level of LA-PF4/beta TG antigen and of creatinine in aorta and in renal vein showed 25%-30% extraction of these compounds by the kidney. Less than 0.1% of the total LA-PF4 antigen injected was recovered in the urine of control rats. In contrast to these results, the clearance of PF4 was not affected by nephrectomy. In conclusion: (1) functional renal tissue is necessary for normal clearance of LA- PF4/beta TG, but renal excretion does not play a major role in its elimination suggesting that the protein is catabolized by the kidney; and (2) catabolic clearance of PF4 does not depend on functioning kidney tissue.

Neutralization of the Antiheparin Activity of Platelet Factor 4 by a Monoclonal Antibody

1992 ◽  
Vol 67 (01) ◽  
pp. 137-143 ◽  
Author(s):  
Leopoldo Saggin ◽  
Flavia Cazzola ◽  
Giuseppe Corona ◽  
Emanuela Salvatico ◽  
Giuseppe Cella ◽  
...  
Keyword(s):  
Disulfide Bonds ◽  
Factor Xa ◽  
Human Platelets ◽  
Platelet Factor 4 ◽  
Molar Ratio ◽  
Rabbit Platelet ◽  
Platelet Factor ◽  
Chromogenic Assay ◽  
Antiheparin Activity ◽  
Human Molecule

SummaryWe have produced a panel of monoclonal antibodies (mAbs) against rabbit platelet factor 4 (PF4). Two of these mAbs have been characterized in this study. In particular the antibody called 10B2, which also recognizes the human molecule, is able to block PF4’s ability to neutralize heparin in a modified Heparin-Factor Xa chromogenic assay. The inhibition appears to be more than 95% at 1:1 mAb/PF4 molar ratio both for purified rabbit and human PF4. Similar results were obtained using supernatants from stimulated human platelets (90% of inhibition at 1:1 mAb/ PF4 molar ratio) or using Fab fragments from 10B2. Studies to determine the antigenic determinant against which 10B2 is directed, show that this is an assembled epitope which involves disulfide bonds of the PF4.

scholarly journals Activated platelets kill Staphylococcus aureus , but not Streptococcus pneumoniae —The role of FcγRIIa and platelet factor 4/heparinantibodies

2020 ◽  
Vol 18 (6) ◽  
pp. 1459-1468 ◽  
Author(s):  
Martina Wolff ◽  
Stefan Handtke ◽  
Raghavendra Palankar ◽  
Jan Wesche ◽  
Thomas P. Kohler ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Streptococcus Pneumoniae ◽  
Platelet Factor 4 ◽  
Platelet Factor ◽  
Activated Platelets

Role of the platelet chemokine platelet factor 4 (PF4) in hemostasis and thrombosis

2010 ◽  
Vol 125 (4) ◽  
pp. 292-296 ◽  
Author(s):  
M. Anna Kowalska ◽  
Lubica Rauova ◽  
Mortimer Poncz
Keyword(s):  
Platelet Factor 4 ◽  
Platelet Factor

Relation Of Heparin Binding And Conformation In PF4 AND LA-PF4 (βTG)

1981 ◽  
Author(s):  
John C Holt ◽  
Marek Kloczewiak ◽  
Daniel A Walz ◽  
Boguslaw Rucinski ◽  
Stefan Niewiarowski
Keyword(s):  
Amino Acid ◽  
Disulfide Bonds ◽  
Amino Acid Sequences ◽  
Platelet Factor 4 ◽  
Heparin Binding ◽  
Platelet Factor ◽  
Significant Difference ◽  
Lysine Residues ◽  
Α Helix ◽  
Β Sheet

Platelet factor 4 (PF4) and low affinity platelet factor 4 (LA-PF4) are platelet-specific secreted proteins that bind to heparin. β-thromboglobulin (βTG) appears to be derived from LA-PF4 by proteolysis of four NH2-terminal residues. PF4 and LA-PF4 (βTG) show 50% sequence homology including four cysteine residues and two pairs of lysine residues near the C00H-terminus which are believed to be responsible for heparin binding. Despite these similarities, the two proteins have markedly different affinities for heparin. We have sought a structural interpretation of this difference by predicting the conformations of 0TG, LA-PF4 and PF4. First, the proportion of residues in α-helical, β-sheet and unordered conformations was estimated from circular dichroism measurements. The results for PF4 and LA-PF4 were experimentally identical, namely 16% α-helix and 20% β-sheet. These values were then applied as experimental constraints in the prediction of the secondary structure of PF4 and LA-PF4 based on their amino acid sequences. This was done by a computer program which compared local amino acid sequence (each residue and 8 residues on either side) with the conformation of similar sequences in 25 proteins of known structure. With the further constraint of the two disulfide bonds in each molecule, models were constructed representing the overall folding of the polypeptide chains. The only significant difference between the two proteins was in the COOH-terminal region of the chains. The models suggest that the lower affinity of LA-PF4 (and βTG) for heparin may result from steric hindrance by the longer and more negatively charged COOH-terminal segments of these molecules compared with PF4.

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