Sarcoendoplasmic reticulum

The only known mechanism for Ca2+ accumulation by the endoplasmic reticulum is by means of sarcoendoplasmic reticulum Ca2+-ATPase (SERCA) pumps 381... 

The plasma membrane Ca2+-ATPase pump effects outward transport of Ca2+ against a large electrochemical gradient for Ca2+. The mechanism of the pump involves its phosphorylation by ATP and the formation of a high-energy intermediate. This basic mechanism is similar for both the plasma membrane and ER pumps however, the structures of these distinct gene products are substantially different. As discussed below, the ER pump, sometimes called a sarcoendoplasmic reticulum Ca2+-ATPase (SERCA) pump, is inhibited potently by certain natural and synthetic toxins that do not affect the plasma membrane pump. The plasma membrane pump, but not the SERCA pump, is controlled in part by Ca2+ calmodulin, allowing for rapid activation when cytoplasmic Ca2+ rises. 

The mode of action of anthranilic diamides has been investigated in detail. It was reported that anthranilic diamides activate RyR, releasing stored calcium from the sarcoendoplasmic reticulum, and exhibit >500-fold differential selectivity toward insect, over mammalian, receptors [32). Anthranilic diamides will be soon classified as RyR modulators within the I RAC classification [2). The two chemical classes, benzenedicarboxamides and anthranilic diamides, could contribute to our understanding of the mechanism of calcium release channels in insects and mammals. 

Like the figure of Greek mythology Sisyphus, ATPase pumps are condemned to push Ca + uphill for eternity into the endoplasmic reticulum (ER) (via sarcoendoplasmic reticular Ca + ATPases SERCA pumps) or out of the cell (via plasma membrane Ca " " ATPases PMCA pumps). There is also a family of Ca " " ATPases (pumps), located in the membranes of the Golgi network (the SPCA pumps). All three belong to the family of P-type ATPases,... 

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