Peroxisomes as novel players in cell calcium homeostasis.
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.
Lasorsa
Francesco Massimo
FM
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.
Pinton
Paolo
P
Palmieri
Luigi
L
Scarcia
Pasquale
P
Rottensteiner
Hanspeter
H
Rizzuto
Rosario
R
Palmieri
Ferdinando
F
D000818:Animals; D019556:COS Cells; D002118:Calcium / Q000378:metabolism*; D002522:Chlorocebus aethiops; D006706:Homeostasis / Q000502:physiology*; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism*; D017136:Ion Transport / Q000502:physiology; D020675:Peroxisomes / Q000378:metabolism*; D011522:Protons; D012964:Sodium / Q000378:metabolism; D025262:Vacuolar Proton-Translocating ATPases / Q000378:metabolism
D011522:Protons; D012964:Sodium; D025262:Vacuolar Proton-Translocating ATPases; D002118:Calcium