The luminal Ca2+ transient controls Ca2+ release/re-uptake of sarcoplasmic reticulum.
Our recent study (Saiki, Y., and Ikemoto, N., Biochemistry 38, 3112-3119, 1999) suggests that Ca2+ release and re-uptake of the released Ca2+ are coordinated. The following results suggest that the coordination is mediated by the luminal Ca2+ ([Ca2+]lum) transient. Upon inducing the release of the passively loaded Ca2+ from the SR with polylysine, the luminal Ca2+ ([Ca2+]lum) first increased then decreased ([Ca2+]lum transient). The activity of the SR Ca2+ ATPase was monitored at different times after inducing Ca2+ release. The phosphoenzyme (EP) formation as determined by the MANT-fluorescence increased concurrently with the initial rapid increase in the [Ca2+]lum. EP decay (pumping turnover) was accelerated concurrently with a decrease of the [Ca2+]lum. The results suggest that the [Ca2+]lum transient serves as a mediator for the acceleration of the Ca2+ re-uptake occurring soon after the induction of Ca2+ release.
Ikemoto
N
N
Boston Biomedical Research Institute, Watertown, Massachusetts 02472, USA.
Yamamoto
T
T
D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000378:metabolism; D000818:Animals; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D002384:Catalysis; D066298:In Vitro Techniques; D008861:Microsomes / Q000378:metabolism; D011817:Rabbits; D012519:Sarcoplasmic Reticulum / Q000201:enzymology / Q000378:metabolism*; D062367:ortho-Aminobenzoates / Q000378:metabolism
D062367:ortho-Aminobenzoates; C045473:3'-O-(N-methylanthraniloyl) ATP; D000255:Adenosine Triphosphate; D000252:Calcium-Transporting ATPases; D002118:Calcium