Open AccessLoss of S100A1 expression leads to Ca 2+ release potentiation in mutant mice with disrupted CaM and S100A1 binding to CaMBD2 of RyR1
Author(s) -
HernándezOchoa Erick O.,
Melville Zephan,
Vanegas Camilo,
Varney Kristen M.,
Wilder Paul T.,
Melzer Werner,
Weber David J.,
Schneider Martin F.
Publication year - 2018
Publication title -
physiological reports
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.918
H-Index - 39
ISSN - 2051-817X
DOI - 10.14814/phy2.13822
Subject(s) - ryr1 , ryanodine receptor , calmodulin , mutant , chemistry , skeletal muscle , biophysics , calcium , stimulation , microbiology and biotechnology , biochemistry , receptor , biology , endocrinology , gene , organic chemistry
Calmodulin (CaM) and S100A1 fine‐tune skeletal muscle Ca 2+ release via opposite modulation of the ryanodine receptor type 1 (RyR1). Binding to and modulation of RyR1 by CaM and S100A1 occurs predominantly at the region ranging from amino acid residue 3614‐3640 of RyR1 (here referred to as Ca MBD 2). Using synthetic peptides, it has been shown that CaM binds to two additional regions within the RyR1, specifically residues 1975‐1999 and 4295‐4325 (Ca MBD 1 and Ca MBD 3, respectively). Because S100A1 typically binds to similar motifs as CaM, we hypothesized that S100A1 could also bind to Ca MBD 1 and Ca MBD 3. Our goals were: (1) to establish whether S100A1 binds to synthetic peptides containing Ca MBD 1 and Ca MBD 3 using isothermal calorimetry ( ITC ), and (2) to identify whether S100A1 and CaM modulate RyR1 Ca 2+ release activation via sites other than Ca MBD 2 in RyR1 in its native cellular context. We developed the mouse model (RyR1D‐S100A1 KO ), which expresses point mutation RyR1‐L3625D (RyR1D) that disrupts the modulation of RyR1 by CaM and S100A1 at Ca MBD 2 and also lacks S100A1 (S100A1 KO ). ITC assays revealed that S100A1 binds with different affinities to Ca MBD 1 and Ca MBD 3. Using high‐speed Ca 2+ imaging and a model for Ca 2+ binding and transport, we show that the RyR1D‐S100A1 KO muscle fibers exhibit a modest but significant increase in myoplasmic Ca 2+ transients and enhanced Ca 2+ release flux following field stimulation when compared to fibers from RyR1D mice, which were used as controls to eliminate any effect of binding at Ca MBD 2, but with preserved S100A1 expression. Our results suggest that S100A1, similar to CaM, binds to Ca MBD 1 and Ca MBD 3 within the RyR1, but that Ca MBD 2 appears to be the primary site of RyR1 regulation by CaM and S100A1.