Regulation of IP3 Receptor-Mediated Calcium Release by Na/K-ATPase
Junctional interaction between plasma membrane receptors and endoplasmic reticulum (ER) IP3 receptors (IP3Rs) plays an essential role in generating specific and robust Ca2+ signaling. Because Na/K-ATPase is an abundant plasma membrane protein that interacts with ER IP3Rs, in this study we determined whether this interaction is required for extracellular stimuli to efficiently regulate ER Ca2+ release. Using cultured pig kidney LLC-PK1 cells as a model we demonstrated that graded knockdown of cellular Na/K-ATPase ?1 subunit resulted in a parallel attenuation of ATP-induced ER Ca2+ release. When the knockdown cells were rescued by knocking in a rat ?1, the expression of rat ?1 not only restored the cellular Na/K-ATPase, but also ATP-induced ER Ca2+ release. Mechanistically, this defect in ATP-induced ER Ca2+ release was neither due to the changes in the amount or the function of cellular IP3 and P2Y receptors nor the ER Ca2+ contents. However, the ?1 knockdown did redistribute cellular IP3 receptors. The pool of IP3 receptors that resided close to the plasma membrane was abolished. Because changes in the plasma membrane proximity could reduce the efficiency of signal transmission from P2Y receptors to ER, we further determined the dose-dependent effects of ATP on PKC? activation and ER Ca2+ release. The data showed that the ?1 knockdown de-sensitized the ATP-induced ER Ca2+ release, but not PKC? activation. Moreover, expression of the N-terminus of Na/K-ATPase ?1 subunit not only disrupted the formation of Na/K-ATPase/IP3R complex, but also abolished the ATP-induced Ca2+ release. Finally, we observed that the ?1 knockdown was also effective in attenuating ER Ca2+ release provoked by angiotensin II and EGF, but not vassopressin. Taken together, our new findings suggest that the interaction between the Na/K-ATPase and IP3 receptors plays an important role in the formation of junctional Ca2+ signaling microdomains.
School:University of Toledo Health Science Campus
School Location:USA - Ohio
Source Type:Master's Thesis
Keywords:na k atpase atp phospholipase c calcium ip3 receptor pkc?
Date of Publication:01/01/2007