Sites and mechanisms of Ca2+ movement in non-excitable cells.
The level of free cytosolic Ca2+ ([Ca2+]i) in cells is firmly established as a second messenger alternative to the cyclic nucleotides. Regulation of the activity of Ca2+ requires the use of membrane transporters of various types which can be classified in terms of their transport rate; channels (fast), carriers (intermediate) and pumps (slow). In general channels are used to elevate [Ca2+]i whereas pumps decrease [Ca2+]i. At physiological membrane potential and Na+ gradients, carriers such as the 3Na+/Ca2+ exchanger also deplete the cell of Ca2+. The carriers could also function in a reverse mode especially with plasma membrane depolarization. Intracellular organelles which can incorporate Ca2+ from and return Ca2+ to the cytosol play a central role in determining [Ca2+]i in resting and stimulated cells. In the resting cell they function as the major Ca2+ buffering system while in the stimulated cell they participate in the dynamic control of [Ca2+]i. The collection of papers in this volume discusses the mechanisms of modulation of cell Ca2+ by these organelles.
Sachs
G
G
Department of Physiology and Membrane Biology, UCLA School of Medicine.
Muallem
S
S
D000818:Animals; D001665:Binding Sites; D001693:Biological Transport, Active; D002118:Calcium / Q000378:metabolism* / Q000502:physiology; D015220:Calcium Channels / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism*; D007295:Inositol Phosphates / Q000502:physiology; D008564:Membrane Potentials; D015388:Organelles / Q000378:metabolism; D011188:Potassium / Q000378:metabolism; D015290:Second Messenger Systems
D015220:Calcium Channels; D007295:Inositol Phosphates; D011188:Potassium; D002118:Calcium