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Published on: November 8, 2024
Intracellular Trafficking, Localization, and Mobilization of Platelet-Borne Thiol Isomerases
Marilena Crescente1, Fred G Pluthero1, Ling Li1
1From the School of Biological Sciences, University of Reading, Reading, United Kingdom (M.C., M.P.S., L.M.H., S.L., M.S.A., S.V., I.M.J., J.M.G.); Program in Cell Biology, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada (F.G.P., L.L., R.W.L., W.H.A.K.); Departments of Paediatrics and Biochemistry, University of Toronto, Toronto, Ontario, Canada (R.W.L., W.H.A.K.); School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom (T.G.W., A.W.P.); and Division of Hematology, Brigham and Women's Hospital, Department of Medicine, Harvard Medical School, Boston, MA (H.F.).
Thiol isomerases move to platelet surfaces via a unique pathway independent of secretory granules, requiring actin polymerization but not membrane fusion. This finding clarifies their role in platelet activation and thrombus formation.
Area of Science:
- Cell Biology
- Hematology
- Protein Biochemistry
Background:
- Thiol isomerases, like protein disulfide isomerase and ERp57, are crucial for protein folding in the endoplasmic reticulum.
- These enzymes are found on activated platelets, influencing aggregation, coagulation, and thrombus formation.
Purpose of the Study:
- To investigate the synthesis and trafficking of thiol isomerases in megakaryocytes.
- To determine the subcellular localization of thiol isomerases within platelets.
- To identify the mechanisms driving thiol isomerase surface translocation upon platelet activation.
Main Methods:
- Immunofluorescence microscopy was employed to visualize thiol isomerases in megakaryocytes and platelets.
- Subcellular fractionation analyzed protein localization in platelets.
- Flow cytometry monitored thiol isomerase mobilization under conditions affecting actin polymerization and membrane fusion.
Main Results:
- Thiol isomerases localize to a distinct compartment in platelets, overlapping with endoplasmic/sarcoplasmic reticulum markers.
- Their trafficking in megakaryocytes is independent of secretory granule contents.
- Mobilization to the platelet surface requires actin polymerization but not SNARE/Munc13-4-mediated fusion.
Conclusions:
- Platelet thiol isomerases reside in a unique subcellular compartment related to the sarcoplasmic reticulum.
- Surface translocation is mediated by actin polymerization, not conventional vesicular fusion.
- This pathway highlights a novel mechanism for regulating platelet surface protein function.
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