Zusammenfassung
Bestrophins form Ca2+-activated Cl- channels and regulate intracellular Ca2+ signaling. We demonstrate that bestrophin 1 is localized in the endoplasmic reticulum (ER), where it interacts with stromal interacting molecule 1, the ER-Ca2+ sensor. Intracellular Ca2+ transients elicited by stimulation of purinergic P2Y(2) receptors in HEK293 cells were augmented by hBest1. The p21-activated protein ...
Zusammenfassung
Bestrophins form Ca2+-activated Cl- channels and regulate intracellular Ca2+ signaling. We demonstrate that bestrophin 1 is localized in the endoplasmic reticulum (ER), where it interacts with stromal interacting molecule 1, the ER-Ca2+ sensor. Intracellular Ca2+ transients elicited by stimulation of purinergic P2Y(2) receptors in HEK293 cells were augmented by hBest1. The p21-activated protein kinase Pak2 was found to phosphorylate hBest1, thereby enhancing Ca2+ signaling and activation of Ca2+-dependent Cl- (TMEM16A) and K+ (SK4) channels. Lack of bestrophin 1 expression in respiratory epithelial cells of mBest1 knockout mice caused expansion of ER cisterns and induced Ca2+ deposits. hBest1 is, therefore, important for Ca2+ handling of the ER store and may resemble the long-suspected counterion channel to balance transient membrane potentials occurring through inositol triphosphate (IP3)-induced Ca2+ release and store refill. Thus, bestrophin 1 regulates compartmentalized Ca2+ signaling that plays an essential role in Best macular dystrophy, inflammatory diseases such as cystic fibrosis, as well as proliferation.
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