The Golgi apparatus is an inositol 1,4,5-trisphosphate-sensitive Ca2+ store, with functional properties distinct from those of the endoplasmic reticulum.
In the past few years, intracellular organelles, such as the endoplasmic reticulum, the nucleus and the mitochondria, have emerged as key determinants in the generation and transduction of Ca2+ signals of high spatio-temporal complexity. Little is known about the Golgi apparatus, despite the fact that Ca2+ within its lumen controls essential processes, such as protein processing and sorting. We report the direct monitoring of the [Ca2+] in the Golgi lumen ([Ca2+]Golgi) of living HeLa cells, using a specifically targeted Ca2+-sensitive photoprotein. With this probe, we show that, in resting cells, [Ca2+]Golgi is approximately 0.3 mM and that Ca2+ accumulation by the Golgi has properties distinct from those of the endoplasmic reticulum (as inferred by the sensitivity to specific inhibitors). Upon stimulation with histamine, an agonist coupled to the generation of inositol 1,4,5-trisphosphate (IP3), a large, rapid decrease in [Ca2+]Golgi is observed. The Golgi apparatus can thus be regarded as a bona fide IP3-sensitive intracellular Ca2+ store, a notion with major implications for the control of organelle function, as well as for the generation of local cytosolic Ca2+ signals.
Pinton
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Department of Biomedical Sciences and CNR Centre for the Study of Biomembranes, University of Padova, Via Colombo 3, 35121 Padova, Italy.
Pozzan
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Rizzuto
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D000331:Aequorin / Q000235:genetics / Q000378:metabolism; D001692:Biological Transport; D002122:Calcium Chloride / Q000494:pharmacology; D020013:Calcium Signaling / Q000502:physiology*; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors / Q000502:physiology; D037282:Calreticulin; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006056:Golgi Apparatus / Q000378:metabolism*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D006367:HeLa Cells; D006801:Humans; D006873:Hydroquinones / Q000494:pharmacology; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism*; D011993:Recombinant Fusion Proteins; D012261:Ribonucleoproteins / Q000235:genetics / Q000378:metabolism; D012799:Sialyltransferases / Q000235:genetics / Q000378:metabolism; D013324:Strontium / Q000494:pharmacology; D019284:Thapsigargin / Q000494:pharmacology; D014638:Vanadates / Q000494:pharmacology
D002135:Calcium-Binding Proteins; D037282:Calreticulin; D004791:Enzyme Inhibitors; D006873:Hydroquinones; D011993:Recombinant Fusion Proteins; D012261:Ribonucleoproteins; C019359:2,5-di-tert-butylhydroquinone; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D014638:Vanadates; D000331:Aequorin; D019284:Thapsigargin; D015544:Inositol 1,4,5-Trisphosphate; D012799:Sialyltransferases; D000252:Calcium-Transporting ATPases; C025700:strontium chloride; D002122:Calcium Chloride; D013324:Strontium