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[Ca2+] microdomains control agonist-induced Ca2+ release in intact HeLa cells
M Montero1, M J Barrero, J Alvarez
1Departamento de Bioquímica y Fisiología, IBGM, Facultad de Medicina, Universidad de Valladolid and CSIC, Spain.
Summary
Local calcium microdomains near release sites inhibit calcium release in cells. This finding is crucial for understanding cellular calcium oscillations and wave generation, impacting cell signaling.
Area of Science:
- Cellular Biology
- Biochemistry
- Physiology
Background:
- Calcium ions (Ca2+) play a critical role in cellular signaling.
- The endoplasmic reticulum (ER) is a major intracellular calcium store.
- Understanding calcium dynamics is essential for cellular function.
Purpose of the Study:
- To investigate the role of local cytosolic calcium ([Ca2+]c) microdomains in regulating calcium release from the ER.
- To determine the impact of agonist stimulation on ER calcium levels in intact cells.
Main Methods:
- Utilized an ER-targeted, low-Ca2+-affinity aequorin to monitor lumenal ER [Ca2+] in HeLa cells.
- Employed BAPTA to clamp cytosolic [Ca2+] and a SERCA inhibitor to assess calcium pumping.
- Analyzed the concentration-dependent effects of histamine on ER calcium release.
Main Results:
- Steady-state ER lumenal [Ca2+] was approximately 600 microM.
- Histamine induced a concentration-dependent decrease in lumenal [Ca2+], with a near tenfold increase in rate when cytosolic [Ca2+] was clamped.
- This effect was independent of altered Ca2+ pumping, suggesting a regulatory mechanism beyond SERCA inhibition.
Conclusions:
- Local cytosolic Ca2+ microdomains at the release site strongly inhibit agonist-induced calcium mobilization.
- This inhibition mechanism is critical for controlling cytosolic Ca2+ oscillations and waves.
- The findings shed light on the generation of spatio-temporal Ca2+ patterns in cellular signaling.