Abstract
Interaction between the endoplasmic reticulum (ER)-located stromal interaction molecue1 (STIM1) and the plasma membrane-located Ca2+ channel subunit, Orai1, underlies store-operated Ca2+ entry (SOCE). Calsequestrin1 (CSQ1), a sarcoplasmic reticulum Ca2+ buffering protein, inhibits SOCE, but the mechanism of action is unknown. We identified an interaction between CSQ1 and STIM1 in HEK293 cells. An increase in monomeric CSQ1 induced by depleted Ca2+ stores, or trifluoperazine (TFP), a blocker of CSQ folding and aggregation, enhanced the CSQ1-STIM1 interaction. In cells with Ca2+ stores depleted, TFP further increased CSQ1 monomerization and CSQ1-STIM1 interaction, but reduced the association of STIM1 with Orai1 and SOCE. Over-expression of CSQ1 or a C-terminal (amino acid 388–396) deletion mutant significantly promoted the association of CSQ1 with STIM1, but suppressed both STIM1-Orai1 interaction and SOCE, while over-expression of the C-terminal (amino acid 362–396) deletion mutant had no effect. The physical interaction between low polymeric forms of CSQ1 and STIM1 likely acts by interfering with STIM1 oligimerization and inhibits STIM1-Orai1 interaction, providing a brake to SOCE under physiological conditions. This novel regulatory mechanism for SOCE may also contribute to the pathological Ca2+ overload in calsequestrin deficient diseases, such as malignant hyperthermia and ventricular tachycardia.
Highlights
Interaction between the endoplasmic reticulum (ER)-located stromal interaction molecue[1] (STIM1) and the plasma membrane-located Ca2+ channel subunit, Orai[1], underlies store-operated Ca2+ entry (SOCE)
We have investigated the relationship between CSQ1 and the essential components of SOCE in HEK293 cells, a cell line in which functional CSQ1 but not CSQ2 expression has been reported[26]
Previous studies have shown that CSQ1 regulates SOCE, and that the aspartate-rich segment is responsible for its interference with the SOCE pathway in skeletal myocytes[24,25]
Summary
Interaction between the endoplasmic reticulum (ER)-located stromal interaction molecue[1] (STIM1) and the plasma membrane-located Ca2+ channel subunit, Orai[1], underlies store-operated Ca2+ entry (SOCE). The physical interaction between low polymeric forms of CSQ1 and STIM1 likely acts by interfering with STIM1 oligimerization and inhibits STIM1Orai[1] interaction, providing a brake to SOCE under physiological conditions This novel regulatory mechanism for SOCE may contribute to the pathological Ca2+ overload in calsequestrin deficient diseases, such as malignant hyperthermia and ventricular tachycardia. The major known molecular components of the SOCE mechanism include the endoplasmic reticulum (ER) membrane-located stromal interaction molecue[1] (STIM1) and the plasma membrane-located Ca2+ release-activated Ca2+ channel pore forming subunit, Orai[13,4]. More recent studies have demonstrated that this SR protein plays a key role in regulating the ryanodine receptor (RyR)-mediated Ca2+ release in skeletal muscle cells It acts as a luminal Ca2+ sensor in regulating RyR activities via its interactions with triadin and junctin[15,16,17]. The mechanism through which CSQ1 exerts its inhibitory effects on SOCE is not known
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
