Calumenin interacts with SERCA2 in rat cardiac sarcoplasmic reticulum.

Calumenin, a multiple EF-hand Ca2+ binding protein is located in the SR of mammalian heart, but the functional role of the protein in the heart is unknown. In the present study, an adenovirus gene transfer system was employed for neonatal rat heart to examine the effects of calumenin over-expression (Calu-OE) on Ca2+ transients. Calu-OE (8 folds) did not alter the expression levels of DHPR, RyR2, NCX, SERCA2, CSQ and PLN. However, Calu-OE affected several parameters of Ca2+ transients. Among them, prolongation of time to 50% baseline (T50) was the most outstanding change in electrically-evoked Ca2+ transients. The higher T50 was due to an inhibition of SERCA2-mediated Ca2+ uptake into SR, as tested by oxalate-supported Ca2+ uptake. Furthermore, co-IP study showed a direct interaction between calumenin and SERCA2. Taken together, calumenin in the cardiac SR may play an important role in the regulation of Ca2+ uptake during the EC coupling process.