Calbindin-D28k and calcium sensing receptor cooperate in MCF-7 human breast cancer cells

  • Authors:
    • Jai Parkash
    • Muhammad A. Chaudhry
    • William B. Rhoten
  • View Affiliations

  • Published online on: May 1, 2004     https://doi.org/10.3892/ijo.24.5.1111
  • Pages: 1111-1119
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Abstract

The metastases of breast cancer cells to bone result in osteolysis and release of Ca2+. Ca2+ as a primary signal transducer can regulate the expression patterns of cell signaling systems. The extracellular calcium ion concentration sensing receptor CaR is a 123 kDa G-protein coupled membrane protein that resides within caveolin-rich regions as a dimer. CaR is involved in regulating several cellular processes such as proliferation, differentiation, secretion, and apoptosis. Calbindin-D28k is a 28 kDa high affinity calcium-binding protein and it is involved in regulating the intracellular calcium ion concentration, [Ca2+]i, and thus influences signal transduction. The role of CaR in sensing and responding to extracellular calcium ion concentration, [Ca2+]o, and neomycin sulfate, and spatial interactions of CaR with calbindin-D28k in MCF-7 human breast cancer cells were studied. Fura-2 loaded MCF-7 cells were exposed to increasing concentrations of CaCl2 or neomycin sulfate and the [Ca2+]i was determined by ratio fluorescence microscopy. The step-wise addition of CaCl2 or neomycin sulfate caused an increase in [Ca2+]i. The normalized dose response curves fitting yielded Hill co-efficient values of 4.32±0.63 and 1.49±0.14 for Ca2+ and neomycin sulfate respectively, thus indicating highly co-operative, 4-5 binding sites for Ca2+ and 1-2 binding site(s) for neomycin sulfate on CaR. The EC50 values were 21±1.6 mM and 43±3.5 µM for CaCl2 and neomycin sulfate respectively. The confocal microscopy data, obtained by using a highly sensitive tyramide signal amplification technology for immunofluorescence detection, showed CaR and calbindin-D28k were co-localized when cells were exposed to 200 µM neomycin sulfate, whereas in control cells there was no co-localization of these two proteins. We hypothesize that sensing and responses to increasing [Ca2+]o that occur through CaR, increase the [Ca2+]i causing the translocation of Ca2+-bound calbindin-D28k towards CaR.

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May 2004
Volume 24 Issue 5

Print ISSN: 1019-6439
Online ISSN:1791-2423

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APA
Parkash, J., Chaudhry, M.A., & Rhoten, W.B. (2004). Calbindin-D28k and calcium sensing receptor cooperate in MCF-7 human breast cancer cells. International Journal of Oncology, 24, 1111-1119. https://doi.org/10.3892/ijo.24.5.1111
MLA
Parkash, J., Chaudhry, M. A., Rhoten, W. B."Calbindin-D28k and calcium sensing receptor cooperate in MCF-7 human breast cancer cells". International Journal of Oncology 24.5 (2004): 1111-1119.
Chicago
Parkash, J., Chaudhry, M. A., Rhoten, W. B."Calbindin-D28k and calcium sensing receptor cooperate in MCF-7 human breast cancer cells". International Journal of Oncology 24, no. 5 (2004): 1111-1119. https://doi.org/10.3892/ijo.24.5.1111