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Visualizing the store-operated channel complex assembly in real time: Identification of SERCA2 as a new member. Cell Calcium 2009; 45:439-46. [DOI: 10.1016/j.ceca.2009.02.010] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2009] [Revised: 02/19/2009] [Accepted: 02/26/2009] [Indexed: 01/12/2023]
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Chandrasekera PC, Kargacin ME, Deans JP, Lytton J. Determination of apparent calcium affinity for endogenously expressed human sarco(endo)plasmic reticulum calcium-ATPase isoform SERCA3. Am J Physiol Cell Physiol 2009; 296:C1105-14. [DOI: 10.1152/ajpcell.00650.2008] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The sarco(endo)plasmic reticulum Ca2+-ATPases (SERCAs) play a crucial role in regulating free cytosolic Ca2+ concentration in diverse cell types. It has been shown that recombinant SERCA3, when measured in heterologous systems, exhibits low apparent affinity for Ca2+; however, Ca2+ affinity of native SERCA3 in an endogenous setting has not been examined. Such a measurement is complicated, because SERCA3 is always coexpressed with the housekeeping isoform SERCA2b. We used a fluorescence-based assay for monitoring continuous Ca2+ uptake into microsomes to examine the properties of endogenous human SERCA3 and SERCA2b. The kinetic parameters were derived using a cooperative two-component uptake model for Ca2+ activation, and the values assigned to SERCA3 were confirmed using the highly specific human SERCA3 inhibitory antibody PL/IM430. First, using recombinant human SERCA3 and SERCA2b proteins transiently expressed in HEK-293 cells, we confirmed the previously observed low apparent Ca2+ affinity for SERCA3 compared with SERCA2b (1.10 ± 0.04 vs. 0.26 ± 0.01 μM), and using mixtures of recombinant protein isoforms, we validated the two-component uptake model. Then we determined apparent Ca2+ affinity for SERCA proteins present endogenously in cultured Jurkat T lymphocytes and freshly isolated human tonsil lymphocytes. The apparent Ca2+ affinity in these two preparations was 1.04 ± 0.07 and 1.1 ± 0.2 μM for SERCA3 and 0.27 ± 0.02 and 0.26 ± 0.01 μM for SERCA2b, respectively. Our data demonstrate, for the first time, that affinity for Ca2+ is inherently lower for SERCA3 expressed in situ than for other SERCA isoforms.
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Corvazier E, Bredoux R, Kovács T, Enouf J. Expression of sarco/endoplasmic reticulum Ca2+ ATPase (SERCA) 3 proteins in two major conformational states in native human cell membranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2009; 1788:587-99. [DOI: 10.1016/j.bbamem.2008.12.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2008] [Revised: 11/29/2008] [Accepted: 12/05/2008] [Indexed: 10/21/2022]
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