Functional interactions between BKCa a-subunit and Annexin A5: implications in apoptosis

Stephen P., Brazier, Telezhkin, Vsevolod ORCID: https://orcid.org/0000-0002-5054-8774 and Kemp, Paul ORCID: https://orcid.org/0000-0003-2773-973X 2016. Functional interactions between BKCa a-subunit and Annexin A5: implications in apoptosis. Oxidative Medicine and Cellular Longevity 2016 , 1607092. 10.1155/2016/1607092

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Abstract

Proteomic studies have suggested a biochemical interaction between the α subunit of the large conductance, voltage- and Ca2+-activated potassium channel (BKCaα) and Annexin A5 (ANXA5), which we verify here by co-immunoprecipitation and double labelling immunocytochemistry. The observation that annexin is flipped to the outer membrane leaflet of the plasma membrane during apoptosis, together with the knowledge that the intracellular C-terminal of the BKCaα contains both a Ca2+-binding and a putative annexin-binding motif, prompted us to investigate the functional consequences of this protein partnership to cell death. Membrane biotinylation demonstrated that ANXA5 was flipped to the outer membrane leaflet of HEK 293 cells early in serum deprivation-evoked apoptosis. As expected, serum deprivation caused caspase 3/7 activation and this was accentuated in BKCaα expressing HEK 293 cells. The functional consequences of ANXA5 partnership with BKCaα were striking, with ANXA5 knockdown causing an increase, and ANXA5 over expression causing a decrease, in single BKCa channel Ca2+-sensitivity, measured in inside-out membrane patches by patch-clamp. Taken together, these data suggest a novel model of the early stages of apoptosis where membrane flippage results in removal of the inhibitory effect of ANXA5 on K+ channel activity with the consequent amplification of Ca2+ influx and augmented activation of caspases.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Biosciences
Subjects:	Q Science > QH Natural history > QH426 Genetics
Uncontrolled Keywords:	Apoptosis, Potassium channel, Annexin, Cell death, Ion channel
Publisher:	Hindawi Publishing Corporation
ISSN:	1942-0900
Date of First Compliant Deposit:	15 August 2016
Date of Acceptance:	10 July 2016
Last Modified:	06 May 2023 04:17
URI:	https://orca.cardiff.ac.uk/id/eprint/93844

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