Orai3 channel is the 2-APB-induced endoplasmic reticulum calcium leak |
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| Affiliation: | 1. Department of Biochemistry, Cinvestav, Mexico City, 07000, Mexico;2. Department of Cell Biology and Development, Instituto de Fisiología Celular, UNAM, Mexico City, 04510, Mexico;3. Laboratory of Cellular Transport Systems, Department of Cellular and Molecular Medicine, KU Leuven, 3000 Leuven, Belgium;4. Biochemistry, Molecular and Structural Biology Section, Department of Chemistry, KU Leuven, 3000 Leuven, Belgium;5. Department of Drug Design and Pharmacology, University of Copenhagen, DK-2100 Copenhagen, Denmark;6. Department of Biomedicine, University of Aarhus, 8000 Aarhus, Denmark;1. Department of Mathematics, University of Auckland, Auckland 1142, New Zealand;2. Department of Pharmacology and Physiology, New Jersey Medical School Rutgers, The State University of New Jersey, Newark, NJ 07103, United States;3. Department of Biochemistry and Molecular Biology, University of Texas Health Science Center at Houston, Houston, Texas 77030,;4. the Cell Biology Graduate Program, University of Texas Medical Branch, Galveston, Texas 77555;6. the Department of Obstetrics and Gynecology, University of Texas Medical Branch, Galveston, Texas 77555,;5. the Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, New York 14642,;12. the Centre for Cancer Research, Westmead Millennium Institute at Westmead Hospital, The University of Sydney, Westmead, New South Wales 2145, Australia;3. From the Department of Cellular and Molecular Physiology, the Pennsylvania State University College of Medicine, Hershey, Pennsylvania 17033 and;4. the Beijing Key Laboratory of Gene Resources and Molecular Development, College of Life Sciences, Beijing Normal University, Beijing 100875, China |
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| Abstract: | We have studied in HeLa cells the molecular nature of the 2-APB induced ER Ca2+ leak using synthetic Ca2+ indicators that report changes in both the cytoplasmic ([Ca2+]i) and the luminal ER ([Ca2+]ER) Ca2+ concentrations. We have tested the hypothesis that Orai channels participate in the 2-APB-induced ER Ca2+ leak that was characterized in the companion paper. The expression of the dominant negative Orai1 E106A mutant, which has been reported to block the activity of all three types of Orai channels, inhibited the effect of 2-APB on the [Ca2+]ER but did not decrease the ER Ca2+ leak after thapsigargin (TG). Orai3 channel, but neither Orai1 nor Orai2, colocalizes with expressed IP3R and only Orai3 channel supported the 2-APB-induced ER Ca2+ leak, while Orai1 and Orai2 inhibited this type of ER Ca2+ leak. Decreasing the expression of Orai3 inhibited the 2-APB-induced ER Ca2+ leak but did not modify the ER Ca2+ leak revealed by inhibition of SERCA pumps with TG. However, reducing the expression of Orai3 channel resulted in larger [Ca2+]i response after TG but only when the ER store had been overloaded with Ca2+ by eliminating the acidic internal Ca2+ store with bafilomycin. These data suggest that Orai3 channel does not participate in the TG-revealed ER Ca2+ leak but forms an ER Ca2+ leak channel that is limiting the overloading with Ca2+ of the ER store. |
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| Keywords: | Orai3 channel Endoplasmic reticulum calcium leak 2-APB Luminal calcium concentration SERCA pump |
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