Sage, SO and Harper, AGS (2021) Calcium sequestration by human platelet acidic organelles is regulated by the actin cytoskeleton and autocrine 5-hydroxytryptamine. Cell Calcium, 101. 102522 - 102522. ISSN 0143-4160

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Abstract

Human platelets regulate agonist-evoked Ca2+ signalling through Ca2+ release from and sequestration into acidic organelles. Previous studies have pharmacologically characterised the presence of a Ca2+-H+ exchanger in these organelles. This exchanger appears to regulate a secondary plateau phase in agonist-evoked cytosolic Ca2+ signals in fura-2-loaded human platelets. Here we demonstrate that cytochalasin D treatment removes the secondary plateau in ADP-evoked Ca2+ signals elicited in the absence of external Ca2+. This effect was reversed by pretreatment with nigericin, a K+/H+ exchanger that short-circuits the Ca2+-H+ exchanger. Using Fluo-5N- or Lysosensor Green-loaded cells, cytochalasin D was found to enhance Ca2+ sequestration into acidic organelles by preventing their alkalinisation. Additional experiments demonstrated that ADP-evoked alkalinisation of acidic organelles and subsequent slowing of acidic organellar Ca2+ sequestration was mediated by autocrine 5-HT signalling. Enhancing this 5-HT signalling using fluoxetine overcame the inhibitory effect of cytochalasin D on ADP-evoked Ca2+ signals, indicating that cytochalasin D interferes with 5-HT autocrine signalling. The ability of Cytochalasin D to interfere with autocrine 5-HT signalling was downstream of the 5-HT2A receptor as secretion of [3H]-5-HT from ADP-stimulated human platelets was not reduced. These data provide the first evidence that the pH gradient across acidic organelles is dynamically regulated upon human platelet activation, and that this can play a significant role in controlling human platelet function by modulating Ca2+-H+ exchange and so [Ca2+]i.

Item Type: Article
Additional Information: The final version of this accepted manuscript and all relevant information related to it, including copyrights, can be found on the publisher website at; 10.1016/j.ceca.2021.102522
Uncontrolled Keywords: Human platelet; Acidic organelle; Calcium sequestration; pH; ADP; 5-hydroxytryptamine
Subjects: R Medicine > R Medicine (General)
R Medicine > R Medicine (General) > R735 Medical education. Medical schools. Research
R Medicine > RM Therapeutics. Pharmacology
R Medicine > RS Pharmacy and materia medica
Depositing User: Symplectic
Date Deposited: 22 Dec 2021 12:31
Last Modified: 25 Feb 2022 12:28
URI: https://eprints.keele.ac.uk/id/eprint/10443

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