Abstract Number: OC 04.5
Meeting: ISTH 2020 Congress
Background: Store-operated calcium entry (SOCE) is the major route of Ca2+ influx in platelets. The Ca2+ sensor stromal interaction molecule 1 (STIM1) triggers SOCE by forming puncta structures with the Ca2+ channel Orai1 and the inositol trisphosphate receptor (IP3R), thereby linking the endo-/sarcoplasmic reticulum to the plasma membrane during SOCE. Several proteins in various cell types have been identified to stabilize this complex and to modulate Ca2+ influx.
Aims: To identify and characterize novel interaction partners of STIM1 in platelets.
Methods: We screened for novel interaction partners of STIM1 in platelet lysates using a recombinant STIM1-C-tail protein, affinity chromatography and mass spectrometry. Subsequently, we generated megakaryocyte- and platelet-specific bridging integrator 2 (BIN2) knockout mice (Bin2fl/fl-Pf4Cre) and assessed the role of BIN2 in a broad range of in vitro platelet experiments and microscopic assays as well as in in vivo models of arterial thrombosis and thrombo-inflammatory brain infarction.
Results: Using affinity chromatography to screen for STIM1 interacting proteins in platelets we identified BIN2, a protein of the BAR domain superfamily. BIN2 deficiency resulted in a markedly reduced Ca2+ store release and hence reduced Ca2+ influx in response to GPCR as well as (hem)ITAM coupled agonists. Although platelet phospholipase C (PLC) activation and IP3 production were normal in BIN2-deficient platelets, impaired IP3R function was detected after stimulating with IP3. Interestingly, thapsigargin mediated SOCE was also defective, indicating a complex interplay between BIN2, IP3R and STIM1/Orai1 complex. These defects translated into impaired thrombus formation under flow and a protection of Bin2fl/fl,Pf4-Cre mice in models of arterial thrombosis, hemostasis and stroke without increasing the risk of intracranial hemorrhage.
Conclusions: BIN2 plays a key role in the activation of IP3R and STIM1 during Ca2+ store depletion and SOCE in platelets. These results establish BIN2 as a central regulator of platelet activation in thrombosis and thrombo-inflammatory disease settings.
To cite this abstract in AMA style:Beck S, Volz J, Voegtle T, Popp M, Kusch C, Meub M, Scheller I, Preu J, Schuhmann MK, Premsler T, Sickmann A, Sauer M, Stegner D, Stoll G, Braun A, Nieswandt B. BIN2 Orchestrates Platelet Calcium Signaling in Thrombosis and Thrombo-inflammation [abstract]. Res Pract Thromb Haemost. 2020; 4 (Suppl 1). https://abstracts.isth.org/abstract/bin2-orchestrates-platelet-calcium-signaling-in-thrombosis-and-thrombo-inflammation/. Accessed May 18, 2021.
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