Activation Of Choline Kinase By Extracellular Ca2+ Is Ca2+-Sensing Receptor, G Alpha(12) And Rho-Dependent In Breast Cancer Cells

Breast cancer cell metastases to bone result in osteolysis and release of large quantities of Ca2+ into the bone microenviroment. Extracellular Ca2+ (Ca-o(2+)) acting through the Ca2+-sensing receptor (CaR), a member of G protein-coupled receptor superfamily, plays an important role in the regulation of multiple signaling pathways. Here, we find that expression of the CaR and G alpha(12) is significantly up-regulated in breast cancer cells (MDA-MB-231 and MCF-7) compared with nonmalignant breast cells (Hs 578Bst and MCF-10A). Ca-o(2+) induces a significant increase in extracellular [H-3]phosphocholine (P-cho) production in breast cancer cells. Using an anti-CaR antibody to block Ca-o(2+) binding to the CaR and small interfering RNA (siRNA) to silence CaR gene expression, our data demonstrate that [H-3]P-cho production in response to Ca-o(2+)-stimulation is CaR- dependent. By analyzing cellular lipid profiles and using siRNA to silence choline kinase (ChoK) expression, we determine that the production of [H-3]P-cho is primarily related to CaR-induced ChoK activation, and not degradation of choline phospholipids. Finally, by pretreatment of the cells with either pertussis toxin or C-3 exoenzyme, co-immunoprecipiation of G alpha(i), G alpha(q) or G alpha(12) with the CaR, and RhoA translocation, we found that the enhancement of ChoK activation and P-cho production in breast cancer cells occurs via a CaR-G alpha(12)-Rho signaling pathway. Published by Elsevier Inc.