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STIM1, an essential and conserved component of store-operated Ca2+ channel function.

Roos J, DiGregorio PJ, Yeromin AV, Ohlsen K, Lioudyno M, Zhang S, Safrina O, Kozak JA, Wagner SL, Cahalan MD, Veliçelebi G, Stauderman KA - J. Cell Biol. (2005)

Bottom Line: RNAi-mediated knockdown of Stim in Drosophila S2 cells significantly reduced TG-dependent Ca2+ entry.Similarly, knockdown of the human homologue STIM1 significantly reduced CRAC channel activity in Jurkat T cells.We propose that STIM1, a ubiquitously expressed protein that is conserved from Drosophila to mammalian cells, plays an essential role in SOC influx and may be a common component of SOC and CRAC channels.

View Article: PubMed Central - PubMed

Affiliation: Torrey Pines Therapeutics, Inc., La Jolla, CA 92037, USA.

ABSTRACT
Store-operated Ca2+ (SOC) channels regulate many cellular processes, but the underlying molecular components are not well defined. Using an RNA interference (RNAi)-based screen to identify genes that alter thapsigargin (TG)-dependent Ca2+ entry, we discovered a required and conserved role of Stim in SOC influx. RNAi-mediated knockdown of Stim in Drosophila S2 cells significantly reduced TG-dependent Ca2+ entry. Patch-clamp recording revealed nearly complete suppression of the Drosophila Ca2+ release-activated Ca2+ (CRAC) current that has biophysical characteristics similar to CRAC current in human T cells. Similarly, knockdown of the human homologue STIM1 significantly reduced CRAC channel activity in Jurkat T cells. RNAi-mediated knockdown of STIM1 inhibited TG- or agonist-dependent Ca2+ entry in HEK293 or SH-SY5Y cells. Conversely, overexpression of STIM1 in HEK293 cells modestly enhanced TG-induced Ca2+ entry. We propose that STIM1, a ubiquitously expressed protein that is conserved from Drosophila to mammalian cells, plays an essential role in SOC influx and may be a common component of SOC and CRAC channels.

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Specificity of STIM1 RNAi in SH-SY5Y cells. (A) Effects of STIM1 RNAi on SOC influx in SH-SY5Y cells. TG-dependent Ca2+ entry in STIM1 siRNA-treated cells (dotted line) is greatly reduced compared with control cells (solid line). Traces from cells treated with vehicle (DMSO) instead of TG were essentially flat (not depicted for clarity). (B) KCl-evoked Ca2+ signals as a measure of voltage-gated Ca2+ channel activity. Data presented as fluo-4 RFUs. At concentrations of 3 mM KCl or below, no significant change in cytosolic Ca2+ was observed. At 10, 20, and 60 mM KCl, a rapid rise in cytosolic Ca2+ was detected. (C) Maximal KCl-evoked RFU values are not different in control and STIM1-knockdown cells. (D) STIM1 suppression does not affect the resting membrane potential or the response to depolarization in SH-SY5Y cells. To monitor changes in membrane potential, a FLIPR membrane potential assay kit (Molecular Devices) was used as per the manufacturer's protocols. Data presented in RFUs. Cells were depolarized with increasing concentration of KCl, as in B. Error bars represent SD.
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fig8: Specificity of STIM1 RNAi in SH-SY5Y cells. (A) Effects of STIM1 RNAi on SOC influx in SH-SY5Y cells. TG-dependent Ca2+ entry in STIM1 siRNA-treated cells (dotted line) is greatly reduced compared with control cells (solid line). Traces from cells treated with vehicle (DMSO) instead of TG were essentially flat (not depicted for clarity). (B) KCl-evoked Ca2+ signals as a measure of voltage-gated Ca2+ channel activity. Data presented as fluo-4 RFUs. At concentrations of 3 mM KCl or below, no significant change in cytosolic Ca2+ was observed. At 10, 20, and 60 mM KCl, a rapid rise in cytosolic Ca2+ was detected. (C) Maximal KCl-evoked RFU values are not different in control and STIM1-knockdown cells. (D) STIM1 suppression does not affect the resting membrane potential or the response to depolarization in SH-SY5Y cells. To monitor changes in membrane potential, a FLIPR membrane potential assay kit (Molecular Devices) was used as per the manufacturer's protocols. Data presented in RFUs. Cells were depolarized with increasing concentration of KCl, as in B. Error bars represent SD.

Mentions: Effects of STIM1 protein suppression were further analyzed in SH-SY5Y cells that express voltage-gated Ca2+ channels (N- and L-type; Reeve et al., 1994). SOC influx in cells treated with the STIM1 siRNA was reduced to <50% of control levels (Fig. 8 A), similar to the effect observed in HEK293 cells. RNAi-mediated knockdown of STIM1 had no significant effect on the peak or kinetics of the KCl-induced Ca2+ signal or on the resting membrane potential of these cells (Fig. 8, B–D), indicating that knockdown of STIM1 did not have a general effect on Ca2+ entry mechanisms and that the effect of STIM1 knockdown on SOC influx was not due to a collapse in membrane potential. Together, these data indicate that STIM1 is required for SOC influx in mammalian cells but does not influence agonist-induced Ca2+ release from IP3-sensitive stores, Ca2+ influx through voltage-gated Ca2+ channels, or the membrane potential.


STIM1, an essential and conserved component of store-operated Ca2+ channel function.

Roos J, DiGregorio PJ, Yeromin AV, Ohlsen K, Lioudyno M, Zhang S, Safrina O, Kozak JA, Wagner SL, Cahalan MD, Veliçelebi G, Stauderman KA - J. Cell Biol. (2005)

Specificity of STIM1 RNAi in SH-SY5Y cells. (A) Effects of STIM1 RNAi on SOC influx in SH-SY5Y cells. TG-dependent Ca2+ entry in STIM1 siRNA-treated cells (dotted line) is greatly reduced compared with control cells (solid line). Traces from cells treated with vehicle (DMSO) instead of TG were essentially flat (not depicted for clarity). (B) KCl-evoked Ca2+ signals as a measure of voltage-gated Ca2+ channel activity. Data presented as fluo-4 RFUs. At concentrations of 3 mM KCl or below, no significant change in cytosolic Ca2+ was observed. At 10, 20, and 60 mM KCl, a rapid rise in cytosolic Ca2+ was detected. (C) Maximal KCl-evoked RFU values are not different in control and STIM1-knockdown cells. (D) STIM1 suppression does not affect the resting membrane potential or the response to depolarization in SH-SY5Y cells. To monitor changes in membrane potential, a FLIPR membrane potential assay kit (Molecular Devices) was used as per the manufacturer's protocols. Data presented in RFUs. Cells were depolarized with increasing concentration of KCl, as in B. Error bars represent SD.
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Related In: Results  -  Collection

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fig8: Specificity of STIM1 RNAi in SH-SY5Y cells. (A) Effects of STIM1 RNAi on SOC influx in SH-SY5Y cells. TG-dependent Ca2+ entry in STIM1 siRNA-treated cells (dotted line) is greatly reduced compared with control cells (solid line). Traces from cells treated with vehicle (DMSO) instead of TG were essentially flat (not depicted for clarity). (B) KCl-evoked Ca2+ signals as a measure of voltage-gated Ca2+ channel activity. Data presented as fluo-4 RFUs. At concentrations of 3 mM KCl or below, no significant change in cytosolic Ca2+ was observed. At 10, 20, and 60 mM KCl, a rapid rise in cytosolic Ca2+ was detected. (C) Maximal KCl-evoked RFU values are not different in control and STIM1-knockdown cells. (D) STIM1 suppression does not affect the resting membrane potential or the response to depolarization in SH-SY5Y cells. To monitor changes in membrane potential, a FLIPR membrane potential assay kit (Molecular Devices) was used as per the manufacturer's protocols. Data presented in RFUs. Cells were depolarized with increasing concentration of KCl, as in B. Error bars represent SD.
Mentions: Effects of STIM1 protein suppression were further analyzed in SH-SY5Y cells that express voltage-gated Ca2+ channels (N- and L-type; Reeve et al., 1994). SOC influx in cells treated with the STIM1 siRNA was reduced to <50% of control levels (Fig. 8 A), similar to the effect observed in HEK293 cells. RNAi-mediated knockdown of STIM1 had no significant effect on the peak or kinetics of the KCl-induced Ca2+ signal or on the resting membrane potential of these cells (Fig. 8, B–D), indicating that knockdown of STIM1 did not have a general effect on Ca2+ entry mechanisms and that the effect of STIM1 knockdown on SOC influx was not due to a collapse in membrane potential. Together, these data indicate that STIM1 is required for SOC influx in mammalian cells but does not influence agonist-induced Ca2+ release from IP3-sensitive stores, Ca2+ influx through voltage-gated Ca2+ channels, or the membrane potential.

Bottom Line: RNAi-mediated knockdown of Stim in Drosophila S2 cells significantly reduced TG-dependent Ca2+ entry.Similarly, knockdown of the human homologue STIM1 significantly reduced CRAC channel activity in Jurkat T cells.We propose that STIM1, a ubiquitously expressed protein that is conserved from Drosophila to mammalian cells, plays an essential role in SOC influx and may be a common component of SOC and CRAC channels.

View Article: PubMed Central - PubMed

Affiliation: Torrey Pines Therapeutics, Inc., La Jolla, CA 92037, USA.

ABSTRACT
Store-operated Ca2+ (SOC) channels regulate many cellular processes, but the underlying molecular components are not well defined. Using an RNA interference (RNAi)-based screen to identify genes that alter thapsigargin (TG)-dependent Ca2+ entry, we discovered a required and conserved role of Stim in SOC influx. RNAi-mediated knockdown of Stim in Drosophila S2 cells significantly reduced TG-dependent Ca2+ entry. Patch-clamp recording revealed nearly complete suppression of the Drosophila Ca2+ release-activated Ca2+ (CRAC) current that has biophysical characteristics similar to CRAC current in human T cells. Similarly, knockdown of the human homologue STIM1 significantly reduced CRAC channel activity in Jurkat T cells. RNAi-mediated knockdown of STIM1 inhibited TG- or agonist-dependent Ca2+ entry in HEK293 or SH-SY5Y cells. Conversely, overexpression of STIM1 in HEK293 cells modestly enhanced TG-induced Ca2+ entry. We propose that STIM1, a ubiquitously expressed protein that is conserved from Drosophila to mammalian cells, plays an essential role in SOC influx and may be a common component of SOC and CRAC channels.

Show MeSH
Related in: MedlinePlus