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Structure‐dynamic basis of splicing‐dependent regulation in tissue‐specific variants of the sodium‐calcium exchanger
Author(s) -
Lee Su Youn,
Giladi Moshe,
Bohbot Hilla,
Hiller Reuben,
Chung Ka Young,
Khananshvili Daniel
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fj.15-282251
Subject(s) - sodium calcium exchanger , rna splicing , calcium , microbiology and biotechnology , alternative splicing , chemistry , sodium–hydrogen antiporter , sodium , computational biology , biophysics , biochemistry , biology , gene , rna , exon , organic chemistry
Tissue‐specific splice variants of Na + /Ca 2+ exchangers contain 2 Ca 2+ ‐binding regulatory domains (CBDs), CBD1 and CBD2. Ca 2+ interaction with CBD1 activates sodium‐calcium exchangers (NCXs), and Ca 2+ binding to CBD2 alleviates Na + ‐dependent inactivation. A combination of mutually exclusive (A, B) and cassette (C‐F) exons in CBD2 raises functionally diverse splice variants through unknown mechanisms. Here, the effect of exons on CBDs backbone dynamics were investigated in the 2‐domain tandem (CBD12) of the brain, kidney, and cardiac splice variants by using hydrogen‐deuterium exchange mass spectrometry and stopped‐flow techniques. Mutually exclusive exons stabilize interdomain interactions in the apoprotein, which primarily predefines the extent of responses to Ca 2+ binding. Deuterium uptake levels were up to 20% lower in the cardiac vs. the brain CBD12, reveling that elongation of the CBD2 FG loop by cassette exons rigidifies the interdomain Ca 2+ salt bridge at the 2‐domain interface, which secondarily modulates the Ca 2+ ‐bound states. In matching splice variants, the extent of Ca 2+ ‐induced rigidification correlates with decreased (up to 10‐fold) Ca 2+ off rates, where the cardiac CBD12 exhibits the slowest Ca 2+ off rates. Collectively, structurally disordered/dynamic segments at mutually exclusive and cassette exons have local and distant effects on the folded structures nearby the Ca 2+ binding sites, which may serve as a structure‐dynamic basis for splicing‐dependent regulation of NCX.—Lee, S. Y., Giladi, M., Bohbot, H., Hiller, R., Chung, K. Y., Khananshvili, D., Structure‐dynamic basis of splicing‐dependent regulation in tissue‐specific variants of the sodium‐calcium exchanger. FASEB J. 30, 1356–1366 (2016). www.fasebj.org