Identification of Key Signaling Molecules Involved in the Activation of the Swelling-Activated Chloride Current in Human Glioblastoma Cells

• DOI: 10.1007/s00232-013-9609-9
• Publication Date: 2013-11-15T08:49:04Z
• Authors: Luigi Catacuzzeno; Antonio Michelucci; Luigi Sforna; Francesco Aiello; Miriam Sciaccaluga; Bernard Fioretti; Emilia Castigli; Fabio Franciolini
• Keywords: 0301 basic medicine; Glioma cells; Diacylglycerol Kinase; Signal transduction; Actins; rac GTP-Binding Proteins; Diglycerides; 03 medical and health sciences; Swelling-activated chloride current; Chlorides; Chloride Channels; Osmotic Pressure; Cell Line, Tumor; Type C Phospholipases; Humans; Protein Multimerization; Glioblastoma; Signal Transduction

The swelling-activated chloride current (I Cl,Vol) is abundantly expressed in glioblastoma (GBM) cells, where it controls cell volume and invasive migration. The transduction pathway mediating I Cl,Vol activation in GBM cells is, however, poorly understood. By means of pharmacological and electrophysiological approaches, on GL-15 human GBM cells we found that I Cl,Vol activation by hypotonic swelling required the activity of a U73122-sensitive phospholipase C (PLC). I Cl,Vol activation could also be induced by the membrane-permeable diacylglycerol (DAG) analog OAG. In contrast, neither calcium (Ca(2+)) chelation by BAPTA-AM nor changes in PKC activity were able to affect I Cl,Vol activation by hypotonic swelling. We further found that R59022, an inhibitor of diacylglycerol kinase (DGK), reverted I Cl,Vol activation, suggesting the involvement of phosphatidic acid. In addition, I Cl,Vol activation required the activity of a EHT1864-sensitive Rac1 small GTPase and the resulting actin polymerization, as I Cl,Vol activation was prevented by cytochalasin B. We finally show that I Cl,Vol can be activated by the promigratory fetal calf serum in a PLC- and DGK-dependent manner. This observation is potentially relevant because blood serum can likely come in contact with glioblastoma cells in vivo as a result of the tumor-related partial breakdown of the blood-brain barrier. Given the relevance of I Cl,Vol in GBM cell volume regulation and invasiveness, the several key signaling molecules found in this study to be involved in the activation of the I Cl,Vol may represent potential therapeutic targets against this lethal cancer.