Relocalization of STIM1 for activation of store-operated Ca(2+) entry is determined by the depletion of subplasma membrane endoplasmic reticulum Ca(2+) store.
STIM1 (stromal interacting molecule 1), an endoplasmic reticulum (ER) protein that controls store-operated Ca(2+) entry (SOCE), redistributes into punctae at the cell periphery after store depletion. This redistribution is suggested to have a causal role in activation of SOCE. However, whether peripheral STIM1 punctae that are involved in regulation of SOCE are determined by depletion of peripheral or more internal ER has not yet been demonstrated. Here we show that Ca(2+) depletion in subplasma membrane ER is sufficient for peripheral redistribution of STIM1 and activation of SOCE. 1 microM thapsigargin (Tg) induced substantial depletion of intracellular Ca(2+) stores and rapidly activated SOCE. In comparison, 1 nM Tg induced slower, about 60-70% less Ca(2+) depletion but similar SOCE. SOCE was confirmed by measuring I(SOC) in addition to Ca(2+), Mn(2+), and Ba(2+) entry. Importantly, 1 nM Tg caused redistribution of STIM1 only in the ER-plasma membrane junction, whereas 1 microM Tg caused a relatively global relocalization of STIM1 in the cell. During the time taken for STIM1 relocalization and SOCE activation, 1 nM Bodipy-fluorescein Tg primarily labeled the subplasma membrane region, whereas 1 microM Tg labeled the entire cell. The localization of Tg in the subplasma membrane region was associated with depletion of ER in this region and activation of SOCE. Together, these data suggest that peripheral STIM1 relocalization that is causal in regulation of SOCE is determined by the status of [Ca(2+)] in the ER in close proximity to the plasma membrane. Thus, the mechanism involved in regulation of SOCE is contained within the ER-plasma membrane junctional region.
Ong
Hwei Ling
HL
Secretory Physiology Section, Gene Therapy and Therapeutics Branch, NIDCR, National Institutes of Health, Bethesda, Maryland 20892, USA.
Liu
Xibao
X
Tsaneva-Atanasova
Krasimira
K
Singh
Brij B
BB
Bandyopadhyay
Bidhan C
BC
Swaim
William D
WD
Russell
James T
JT
Hegde
Ramanujan S
RS
Sherman
Arthur
A
Ambudkar
Indu S
IS
D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism*; D004594:Electrophysiology; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D005786:Gene Expression Regulation; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism / Q000502:physiology*; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D009363:Neoplasm Proteins / Q000378:metabolism / Q000502:physiology*; D010766:Phosphorylation; D000071737:Stromal Interaction Molecule 1; D019284:Thapsigargin / Q000494:pharmacology; D013997:Time Factors; D019892:eIF-2 Kinase / Q000378:metabolism
D002118:Calcium; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D000071737:Stromal Interaction Molecule 1; D019284:Thapsigargin; D019892:eIF-2 Kinase; C103530:STIM1 protein, human