Peroxisomes as novel players in cell calcium homeostasis |
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Authors: | Lasorsa Francesco Massimo Pinton Paolo Palmieri Luigi Scarcia Pasquale Rottensteiner Hanspeter Rizzuto Rosario Palmieri Ferdinando |
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Institution: | Department of Pharmaco-Biology, Laboratory of Biochemistry and Molecular Biology, University of Bari and CNR Institute of Biomembranes and Bioenergetics, Via Orabona 4, Bari, Italy. |
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Abstract: | Ca2+ concentration in peroxisomal matrix (Ca2+](perox)) has been monitored dynamically in mammalian cells expressing variants of Ca2+-sensitive aequorin specifically targeted to peroxisomes. Upon stimulation with agonists that induce Ca2+ release from intracellular stores, peroxisomes transiently take up Ca2+ reaching peak values in the lumen as high as 50-100 microm, depending on cell types. Also in resting cells, peroxisomes sustain a Ca2+ gradient, Ca2+](perox) being approximately 20-fold higher than Ca2+] in the cytosol (Ca2+](cyt)). The properties of Ca2+ traffic across the peroxisomal membrane are different from those reported for other subcellular organelles. The sensitivity of peroxisomal Ca2+ uptake to agents dissipating H+ and Na+ gradients unravels the existence of a complex bioenergetic framework including V-ATPase, Ca2+/H+, and Ca2+/Na+ activities whose components are yet to be identified at a molecular level. The different Ca2+](perox) of resting and stimulated cells suggest that Ca2+ could play an important role in the regulation of peroxisomal metabolism. |
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