Rat vas deferens SERCA2 is modulated by Ca2+/calmodulin protein kinase II-mediated phosphorylation

Abstract

Ca2+ pumps are important players in smooth muscle contraction. Nevertheless, little information is available about these pumps in the vas deferens. We have determined which subtype of sarco(endo)plasmic reticulum Ca2+-ATPase isoform (SERCA) is expressed in rat vas deferens (RVD) and its modulation by calmodulin (CaM)-dependent mechanisms. The thapsigargin-sensitive Ca2+-ATPase from a membrane fraction containing the highest SERCA levels in the RVD homogenate has the same molecular mass (∼115 kDa) as that of SERCA2 from the rat cerebellum. It has a very high affinity for Ca2+ (Ca0.5 = 780 nM) and a low sensitivity to vanadate (IC50 = 41 µM). These facts indicate that SERCA2 is present in the RVD. Immunoblotting for CaM and Ca2+/calmodulin-dependent protein kinase II (CaMKII) showed the expression of these two regulatory proteins. Ca2+ and CaM increased serine-phosphorylated residues of the 115-kDa protein, indicating the involvement of CaMKII in the regulatory phosphorylation of SERCA2. Phosphorylation is accompanied by an 8-fold increase of thapsigargin-sensitive Ca2+ accumulation in the lumen of vesicles derived from these membranes. These data establish that SERCA2 in the RVD is modulated by Ca2+ and CaM, possibly via CaMKII, in a process that results in stimulation of Ca2+ pumping activity.

Ivermectin as an inhibitor of the plasma membrane and the sarcoplasmic/endoplasmic reticulum Ca2+-ATPases in rat vas deferens

“…The molecular evidence for Ca 2+ homeostasis on rat vas deferens function has been demonstrated previously: (1) subcellular fractions obtained from rat vas deferens homogenate contain vesicles of SR origin presenting SERCA pumps, RyR and IP 3 R 18 ; (2) the isoform of the SERCA pump expressed in rat vas deferens is probably SERCA2b 11,19 ; and (3) treatment at 37°C and pH 7.4 is sufficient to dissociate the FKBP12-CRC complex in rat vas deferens 12 . The aim of this work was to demonstrate the effect of ivermectin on Ca 2+ -ATPase activity and Ca 2+ content of SR vesicles of rat vas deferens in the presence or in the absence of FKBP12-CRC complex.…”

“…Finally, our group recently demonstrated that chronic malnutrition affected several components related to intracellular Ca 2+ handling in vas deferens, reducing the haploid cell count in this organ and decreasing the reproductive capacity of the male adult Wistar rats 6 . [7][8][9][10][11] . Both the efflux and the influx of Ca 2+ from intracellular stocks are well regulated by the 12 kDa FK506 Binding Protein (FKBP12), an immunophilin located in the cytoplasm of cells, that is the pharmacological receptor for the immunosuppressant drugs FK506 (tacrolimus) and rapamycin 12 .…”