Super-Resolution Modeling of Calcium Release in Heart

Abstract

Urotensin-II (U-II) is a vasoactive peptide with many effects in the cardiovascular system. It has been described to induce vascular smooth muscle cell (SMC) proliferation, and is involved in the pathogenesis of atherosclerosis, restenosis, and vascular remodelling; however, its signalling pathway still remains unclear. The aim of this study was to elucidate the role of calcium (Ca 2þ)-dependent signalling and alternative signalling pathways in UIIevoked VSMCs proliferation, focussing our attention on store-operated Ca 2þ entry (SOCE) pathway and epithelium growth factor receptor (EGFR) transactivation. We used 5-bromo-2-deoxyuridine (BrdU) labeling, molecular knockdown with small interfering RNA (siRNA) and immunofluorescence to study UIIpromoted aortic SMC proliferation. Ca 2þ mobilization assays were performed to study Ca 2þ entry in cultured SMC. We found that UII enhanced intracellular Ca 2þ concentration ([Ca 2þ ]i) which was significantly reduced by classical SOCE inhibitors and by knockdown of essential components of the SOCE such as STIM1, Orai1, or TRPC1. Moreover, UII stimulated SMC proliferation and Ca 2þ /cAMP response elementbinding protein (CREB) activation through SOCE pathway that involved STIM1, Orai1, and TRPC1. Co-immunoprecipitation experiments showed that UII promoted the association between Orai1 and STIM1, and between Orai1 and TRPC1. Additionally, we determined that epithelium growth factor receptor (EGFR) transactivation, extracellular signal-regulated kinase (ERK) and Ca 2þ /calmodulin-dependent kinase (CaMK) signaling pathways were involved in UII-mediated Ca 2þ influx, CREB activation and VSMCs proliferation. Our data show for the first time that UII-induced SMC proliferation and CREB activation requires a complex signalling pathway that involves on the one hand SOCE mediated by STIM1, Orai1 and TRPC1, and on the other hand EGFR, ERK, and CaMK activation.

Ryanodine receptor sensitivity governs the stability and synchrony of local calcium release during cardiac excitation-contraction coupling

“…Additionally, we have updated our luminal Ca 2+ sensitivity function, ϕ (see Eq. (S45) and Walker et al, 2014 [58]), which reflects the most recent biophysical characterizations of RyR2 gating with varied luminal Ca 2+ levels. With normal or reduced SR Ca 2+ content ϕ has minimal effect on RyR2 P O , however, during SR Ca2+ overload ϕ results in a drastic increase in RyR2 P O , see Fig.…”

The Ryanodine Receptor Patchwork: Knitting Calcium Spark Dynamics

“…The discussion of disease suggests additional ways in which future research can build off the study by Walker et al (4). It will be important for future studies to move beyond the Ca 2þ spark level by incorporating multiple, spatially specified CRUs within the same model.…”

“…In this way such a model could predict how irregularity in the RyR cluster influences the likelihood that local Ca 2þ sparks may initiate regenerative, potentially arrhythmogenic Ca 2þ waves. Despite this limitation, which will certainly be addressed going forward, the interesting study presented in this issue (4) provides an excellent example of how mathematical modeling can be used both as a tool for synthesizing existing experimental data and as a means of predicting experiments that have not yet been performed. Experimental data are always required to build and constrain models, but when models are constructed thoughtfully, they can enable better interpretation of new data.…”