Dataset Information

STIM is a Ca2+ sensor essential for Ca2+-store-depletion-triggered Ca2+ influx.

ABSTRACT: Ca(2+) signaling in nonexcitable cells is typically initiated by receptor-triggered production of inositol-1,4,5-trisphosphate and the release of Ca(2+) from intracellular stores. An elusive signaling process senses the Ca(2+) store depletion and triggers the opening of plasma membrane Ca(2+) channels. The resulting sustained Ca(2+) signals are required for many physiological responses, such as T cell activation and differentiation. Here, we monitored receptor-triggered Ca(2+) signals in cells transfected with siRNAs against 2,304 human signaling proteins, and we identified two proteins required for Ca(2+)-store-depletion-mediated Ca(2+) influx, STIM1 and STIM2. These proteins have a single transmembrane region with a putative Ca(2+) binding domain in the lumen of the endoplasmic reticulum. Ca(2+) store depletion led to a rapid translocation of STIM1 into puncta that accumulated near the plasma membrane. Introducing a point mutation in the STIM1 Ca(2+) binding domain resulted in prelocalization of the protein in puncta, and this mutant failed to respond to store depletion. Our study suggests that STIM proteins function as Ca(2+) store sensors in the signaling pathway connecting Ca(2+) store depletion to Ca(2+) influx.

SUBMITTER: Liou J

PROVIDER: S-EPMC3186072 | biostudies-literature | 2005 Jul

REPOSITORIES: biostudies-literature

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STIM is a Ca2+ sensor essential for Ca2+-store-depletion-triggered Ca2+ influx.

Liou Jen J Kim Man Lyang ML Heo Won Do WD Jones Joshua T JT Myers Jason W JW Ferrell James E JE Meyer Tobias T

Current biology : CB 20050701 13

Ca(2+) signaling in nonexcitable cells is typically initiated by receptor-triggered production of inositol-1,4,5-trisphosphate and the release of Ca(2+) from intracellular stores. An elusive signaling process senses the Ca(2+) store depletion and triggers the opening of plasma membrane Ca(2+) channels. The resulting sustained Ca(2+) signals are required for many physiological responses, such as T cell activation and differentiation. Here, we monitored receptor-triggered Ca(2+) signals in cells t ...[more]

PMID: 16005298

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Project description:The KRAS GTPase plays a fundamental role in transducing signals from plasma membrane growth factor receptors to downstream signalling pathways controlling cell proliferation, survival and migration. Activating KRAS mutations are found in 20% of all cancers and in up to 40% of colorectal cancers, where they contribute to dysregulation of cell processes underlying oncogenic transformation. Multiple KRAS-regulated cell functions are also influenced by changes in intracellular Ca2+ levels that are concurrently modified by receptor signalling pathways. Suppression of intracellular Ca2+ release mechanisms can confer a survival advantage in cancer cells, and changes in Ca2+ entry across the plasma membrane modulate cell migration and proliferation. However, inconsistent remodelling of Ca2+ influx and its signalling role has been reported in studies of transformed cells. To isolate the interaction between altered Ca2+ handling and mutated KRAS in colorectal cancer, we have previously employed isogenic cell line pairs, differing by the presence of an oncogenic KRAS allele (encoding KRASG13D), and have shown that reduced Ca2+ release from the ER and mitochondrial Ca2+ uptake contributes to the survival advantage conferred by oncogenic KRAS. Here we show in the same cell lines, that Store-Operated Ca2+ Entry (SOCE) and its underlying current, ICRAC are under the influence of KRASG13D. Specifically, deletion of the oncogenic KRAS allele resulted in enhanced STIM1 expression and greater Ca2+ influx. Consistent with the role of KRAS in the activation of the ERK pathway, MEK inhibition in cells with KRASG13D resulted in increased STIM1 expression. Further, ectopic expression of STIM1 in HCT 116 cells (which express KRASG13D) rescued SOCE, demonstrating a fundamental role of STIM1 in suppression of Ca2+ entry downstream of KRASG13D. These results add to the understanding of how ERK controls cancer cell physiology and highlight STIM1 as an important biomarker in cancerogenesis.

Project description:Previous studies in non-excitable cells have suggested that depletion of internal Ca2+ stores activates Ca2+ influx from the extracellular space via a mechanism that does not require stimulation of phosphoinositide hydrolysis. To test this hypothesis in vascular endothelial cells, the effect of the Ca(2+)-ATPase/pump inhibitor 2,5-di-t-butylhydroquinone (BHQ) on cytosolic free Ca2+ concentration ([Ca2+]i) was examined. BHQ produced a dose-dependent increase in [Ca2+]i, which remained elevated over basal values for several minutes and was substantially inhibited in the absence of extracellular Ca2+. Application of bradykinin after BHQ demonstrated that the BHQ-sensitive compartment partially overlapped the bradykinin-sensitive store. Similar results were obtained with thapsigargin and cyclopiazonic acid, two other Ca(2+)-ATPase inhibitors. Although BHQ had no effect on phosphoinositide hydrolysis, both 45Ca2+ influx and efflux were stimulated by this agent. These results suggest that depletion of the agonist-sensitive Ca2+ store is sufficient for activation of Ca2+ influx. Several characteristics of the Ca(2+)-influx pathway activated by internal store depletion were compared with those of the agonist-activated pathway. Bradykinin-stimulated Ca2+ influx was increased at alkaline extracellular pH (pHo), and was inhibited by extracellular La3+, by depolarization of the membrane, and by the novel Ca(2+)-influx blocker 1-(beta-[3-(4-methoxyphenyl)propoxy]-4- methoxyphenethyl)-1H-imidazole hydrochloride (SKF 96365). Additionally, bradykinin stimulated influx of both 45Ca2+ and 133Ba2+, consistent with the hypothesis that the agonist-activated influx pathway is permeable to both of these bivalent cations. Likewise, activation of Ca2+ influx by BHQ, thapsigargin and cyclopiazonic acid was blocked by La3+, membrane depolarization and SKF 96365, but was unaffected by nitrendipine or BAY K 8644. Furthermore, Ca2+ influx stimulated by BHQ was increased at alkaline pHo and BHQ stimulated the influx of both 45Ca2+ and 133Ba2+ to the same extent. These results demonstrate that the agonist-activated Ca(2+)-influx pathway and the pathway activated by depletion of the agonist-sensitive internal Ca2+ store are indistinguishable.

Dataset Information

STIM is a Ca2+ sensor essential for Ca2+-store-depletion-triggered Ca2+ influx.

Publications

STIM is a Ca2+ sensor essential for Ca2+-store-depletion-triggered Ca2+ influx.

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