In situ modulation of the human cardiac ryanodine receptor (hRyR2) by FKBP12.6

George, Christopher, Sorathia, Rina, Bertrand, Benedicte M. A. and Lai, Francis Anthony ORCID: https://orcid.org/0000-0003-2852-8547 2003. In situ modulation of the human cardiac ryanodine receptor (hRyR2) by FKBP12.6. Biochemical Journal 370 (2) , pp. 579-589. 10.1042/BJ20021433

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Abstract

The ryanodine receptor complex (RyR), a large oligomeric assembly that functions as a Ca2+-release channel in the sarcoplasmic reticulum (SR)/endoplasmic reticulum (ER), comprises four RyR subunits and four FK506-binding proteins (FKBP). The precise mode of interaction and modulation of the cardiac RyR (RyR2) channel by FKBP12/FKBP12.6 remains to be fully defined. We have generated a series of Chinese-hamster ovary (CHO) cell lines stably expressing discrete levels of recombinant human RyR2 (hRyR2) (CHOhRyR2). Confocal microscopy of CHOhRyR2 cells co-expressing either FKBP12 or FKBP12.6 demonstrated that FKBP12.6 was sequestered from the cytoplasm to ER membranes as the cellular levels of hRyR2 increased. There was negligible hRyR2-induced subcellular redistribution of FKBP12. The magnitude of Ca2+ release in CHOhRyR2 cells in response to stimulation by 4-chloro-m-cresol was in direct proportion to the expression levels of hRyR2. However, in CHOhRyR2 cells co-expressing FKBP12.6, Ca2+ release triggered by the addition of 4-chloro-m-cresol was markedly decreased. In contrast, co-expression of FKBP12 did not affect agonist-induced Ca2+ release in CHOhRyR2 cells. Resting cytoplasmic [Ca2+] in CHOhRyR2 remained unaltered after co-expression of FKBP12 or FKBP12.6, but estimation of the ER Ca2+ load status showed that co-expression of FKBP12.6, but not FKBP12, promoted superfilling of the ER Ca2+ store which could not be released by RyR2 after agonist activation. The effects of FKBP12.6 on hRyR2-mediated intracellular Ca2+ handling could be antagonized using rapamycin (5µM). These results suggest that FKBP12.6 associates with hRyR2 in situ to modulate precisely the functionality of hRyR2 Ca2+-release channel.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Medicine
Uncontrolled Keywords:	channel regulation ; FK506-binding protein ; intracellular Ca2+ homoeostasis ; ryanodine receptor.
Publisher:	Biochemical Society
ISSN:	0264-6021
Last Modified:	17 Oct 2022 08:23
URI:	https://orca.cardiff.ac.uk/id/eprint/33

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