Intracellular Ca2+ stores in neurons. Identification and functional aspects.
Various aspects of the rapidly exchanging intracellular Ca2+ stores of neurons and nerve cells are reviewed: their multiplicity, with separate sensitivity to either the second messenger, inositol 1,4,5-trisphosphate, or ryanodine-caffeine (the latter stores are probably activated via Ca(2+)-induced Ca2+ release); their control of the plasma membrane Ca2+ permeability, via the activation of a peculiar type of cation channels; their ability to sustain localized heterogeneities of the [Ca2+]i that could be of physiological key-importance. Finally, the molecular composition of these stores is discussed. They are shown (by high resolution immunocytochemistry and subcellular fractionation) to express: i) a Ca2+ ATPase responsible for the accumulation of the cation; ii) Ca2+ binding protein(s) of low affinity and high capacity to keep Ca2+ stored; and iii) a Ca2+ channel, activated by either one of the mechanisms mentioned above, to release Ca2+ to the cytosol. Results obtained in Purkinje neurons document the heterogeneity of the stores and the strategical distribution of the corresponding organelles (calciosomes; specialized portions of the ER) within the cell body, dendrites and dendritic spines.
Department of Pharmacology, CNR Cytopharmacology, Milan, Italy.
J
J
Meldolesi
A
A
Villa
P
P
Podini
E
E
Clementi
D
D
Zacchetti
P
P
D'Andrea
P
P
Lorenzon
F
F
Grohovaz
D000818:Animals; D002118:Calcium / Q000378:metabolism* / Q000502:physiology*; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism*; D007700:Kinetics; D009474:Neurons / Q000378:metabolism*; D015388:Organelles / Q000378:metabolism
D002118:Calcium