Organellar Calcium Buffers

Calcium signaling in pancreatic β-cells in health and in Type 2 diabetes

“…Although SERCAs contribute to most of the uptake of Ca 2+ by the ER, a small contribution of another Ca 2+ transporter, SPCA (see below), is possible [90]. It is generally admitted that, within the ER, the total concentration of Ca 2+ is ∼2 mM, with free [Ca 2+ ] in the range of 50-500 M and the remainder buffered by ER resident proteins such as calreticulin, calnexin, 78-kDa glucose-regulated protein/immunoglobulin heavy chain binding protein (GRP78 also known as BiP), GRP94, and various protein disulfide isomerases (PDI, such as GRP58/ERp57) [91][92][93][94]. These proteins are not simply Ca 2+ buffers but they also serve as ER chaperone or folding proteins and their function is regulated by Ca 2+ .…”

Calcium Signaling in Cardiac Myocytes

“…The critical role of CSQ in Ca 2þ storage was shown by the increase or decrease in SR Ca 2þ load observed in experiments in which CSQ expression was enhanced or suppressed, respectively (Terentyev et al 2003). In addition to acting as the major Ca 2þ storage protein in cardiac muscle, CSQ also regulates RyR channel activity (Prins and Michalak 2011 CaM is an important regulator of the RyR in cardiac myocytes, both in its Ca 2þ bound and Ca 2þ free form (Ca-CaM and apo-CaM, respectively). The binding site for CaM on the RyR was mapped to the carboxyl terminal of the receptor by site-directed mutagenesis (Porter Moore et al 1999a;Porter Moore et al 1999b), in agreement with cryo-EM studies (Wagenknecht et al 1997).…”

Endoplasmic reticulum stress and calcium imbalance are involved in cadmium-induced lipid aberrancy in Saccharomyces cerevisiae

“…Interestingly, the ERassociated proteins are involved in maintaining ER calcium homeostasis. The molecular chaperones such as calreticulin, GRP94 or BiP, and folding enzymes (protein disulfide isomerases [PDI]) contribute to Ca 2+ buffering in the ER lumen (Prins and Michalak 2011).…”