Plasma membrane Ca2+-ATPase in excitable and nonexcitable cells.
There is a significant number of data confirming that the maintenance of calcium homeostasis in a living cell is a complex, multiregulated process. Calcium efflux from excitable cells (i.e., neurons) occurs through two main systems--an electrochemically driven Na+/Ca2+ exchanger with a low Ca2+ affinity (K0.5 = 10-15 microM), and a plasmalemmal, specific Ca2+-ATPase, with a high Ca2+ affinity (K0.5 < 0.5-1 microM), whereas in nonexcitable cells (i.e., erythrocytes) the calcium pump is the sole system responsible for the extrusion of calcium ions. The plasma membrane Ca2+-ATPase (PMCA) is a ubiquitously expressed protein, and more than 26 transcripts of four PMCA genes are distributed in a tissue specific manner. Differences in the structure and localization of PMCA variants are thought to correlate with specific regulatory properties and may have consequences for proper cellular Ca2+ signaling. The regulatory mechanisms of calcium pump activity have been studied extensively, resulting in a new view of the functioning of this important molecule in the membranes.
Zylińska
L
L
Department of Biochemistry, Medical University, Lódź, Poland. luska@psk2.am.lodz.pl
Soszyński
M
M
D000818:Animals; D001921:Brain / Q000187:drug effects / Q000201:enzymology; D020013:Calcium Signaling; D000252:Calcium-Transporting ATPases / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000201:enzymology; D006706:Homeostasis; D006801:Humans; D066298:In Vitro Techniques; D007527:Isoenzymes / Q000378:metabolism; D010766:Phosphorylation; D017382:Reactive Oxygen Species / Q000378:metabolism; D013256:Steroids / Q000494:pharmacology
D007527:Isoenzymes; D017382:Reactive Oxygen Species; D013256:Steroids; D000252:Calcium-Transporting ATPases