Novel Insights in the Regulation of Phosphatidylserine Exposure in Human Red Blood Cell

Title: Novel Insights in the Regulation of Phosphatidylserine Exposure in Human Red Blood Cell
Authors: Wesseling, M.C.
Wagner-Britz, L.
Nguyen, D.B., (...)
Kaestner, L.
Bernhardt, I.
Keywords: Ca2+ content;Flow cytometry;Fluorescence imaging;Phosphatidylserine exposure;Protein kinase C;Red blood cells
Issue Date: 2016
Publisher: S. Karger AG
Citation: Scopus
Abstract: In previous publications we were able to demonstrate the exposure of phosphatidylserine (PS) in the outer membrane leaflet after activation of red blood cells (RBCs) by lysophosphatidic acid (LPA), phorbol-12 myristate-13acetate (PMA), or 4-bromo-A23187 (A23187). It has been concluded that three different mechanisms are responsible for the PS exposure in human RBCs: (i) Ca2+-stimulated scramblase activation (and flippase inhibition) by A23187, LPA, and PMA; (ii) PKCα activation by LPA and PMA; and (iii) enhanced lipid flip flop caused by LPA. Further studies aimed to elucidate interconnections between the increased Ca2+ content, scramblase- and PKCα-activation. In addition, the role of the Ca2+-activated K+ channel (Gardos channel) activity in the process of PS exposure needs to be investigated. Methods: The intracellular Ca2+ content and the PS exposure of RBCs have been investigated after treatment with LPA (2.5 μM), PMA (6 μM), or A23187 (2 μM). Fluo-4 and annexin V-FITC has been used to detect intracellular Ca2+ content and PS exposure, respectively. Both parameters (Ca2+ content, PS exposure) were studied using flow cytometry. Inhibitors of the scramblase, the PKCα, and the Gardos channel have been applied. Results: The percentage of RBCs showing PS exposure after activation with LPA, PMA, or A23187 is significantly reduced after inhibition of the scramblase using the specific inhibitor R5421 as well as after the inhibition of the PKCα using chelerythrine chloride or calphostin C. The inhibitory effect is more pronounced when the scramblase and the PKCα are inhibited simultaneously. Additionally, the inhibition of the Gardos channel using charybdotoxin resulted in a significant reduction of the percentage of RBCs showing PS exposure under all conditions measured. Similar results were obtained when the Gardos channel activity was suppressed by increased extracellular K+ content. Conclusion: PS exposure is mediated by the Ca2+-dependent scramblase but also by PKCα activated by LPA and PMA in a Ca2+-dependent and a Ca2+-independent manner. Furthermore, we hypothesize that a hyperpolarisation of RBCs caused by the opening of the Gardos channel is essential for the scramblase activity as well as for a fraction of the LPA-induced Ca2+ entry.
Description: Cellular Physiology and Biochemistry Volume 39, Issue 5, 1 November 2016, Pages 1941-1954
URI: https://www.karger.com/Article/FullText/447891
http://repository.vnu.edu.vn/handle/VNU_123/33272
ISSN: 10158987
Appears in Collections:Bài báo của ĐHQGHN trong Scopus

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