Identification of key signaling molecules involved in the activation of the swelling-activated chloride current in human glioblastoma cells.
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.
Dipartimento di Biologia Cellulare e Ambientale, Universita' di Perugia, Via Pascoli 1, 06123, Perugia, Italy, luigi.catacuzzeno@unipg.it.
Luigi
L
Catacuzzeno
Antonio
A
Michelucci
Luigi
L
Sforna
Francesco
F
Aiello
Miriam
M
Sciaccaluga
Bernard
B
Fioretti
Emilia
E
Castigli
Fabio
F
Franciolini
D000199:Actins / Q000378:metabolism; D045744:Cell Line, Tumor; D018118:Chloride Channels / Q000378:metabolism*; D002712:Chlorides / Q000378:metabolism; D019852:Diacylglycerol Kinase / Q000378:metabolism; D004075:Diglycerides / Q000096:biosynthesis; D005909:Glioblastoma / Q000378:metabolism*; D006801:Humans; D009997:Osmotic Pressure; D055503:Protein Multimerization; D015398:Signal Transduction; D010738:Type C Phospholipases / Q000378:metabolism; D020744:rac GTP-Binding Proteins / Q000378:metabolism
D000199:Actins; D018118:Chloride Channels; D002712:Chlorides; D004075:Diglycerides; D019852:Diacylglycerol Kinase; D010738:Type C Phospholipases; D020744:rac GTP-Binding Proteins