A novel function of BCL-2 overexpression in regulatory volume decrease. Enhancing swelling-activated Ca(2+) entry and Cl(-) channel activity.
The cellular function of the oncogene bcl-2, a key regulator of apoptosis, is still debated. The goal of this study was to explore the relationship between BCL-2 overexpression and cell volume regulation by using two independent models, Madin-Darby canine kidney (MDCK) cells stably transfected with BCL-2 and MDCK clones with inducible BCL-2 expression by the lac operator/repressor. BCL-2 overexpression enhanced the capability of regulatory volume decrease (RVD), a cellular defensive process against hypotonic stress. In various clones of MDCK cells, hypotonic stress induced an outwardly rectified Cl(-) current that was significantly up-regulated by BCL-2 overexpression. Other fundamental characteristics of this channel were similar among different MDCK clones, such as sensitivity to Cl(-) channel inhibitor, anion permeability, and time-dependent inactivation at more positive potential. Most importantly, BCL-2 overexpression up-regulates the swelling-activated Ca(2+) transient that is a critical signaling for normal RVD and the activation of swelling-activated Cl(-) channel in MDCK cells. BCL-2 overexpression also enhances the capacitative Ca(2+) entry that can be differentiated from the swelling-activated Ca(2+) transient by kinetic analysis and sensitivity to Gd(3+). Moreover, neutralization of endogenous BCL-2 by antibody blocks the normal RVD response and the activation of swelling-activated Cl(-) channel in human cervical cancer HT-3 cells. These results provide a new insight into the novel function of BCL-2 overexpression in the regulation of cell volume and ion flux.
Shen
Meng-Ru
MR
Department of Obstetrics and Gynecology, National Cheng Kung University Medical College, Tainan 701, Taiwan, Republic of China.
Yang
Tzi-Peng
TP
Tang
Ming-Jer
MJ
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D048429:Cell Size / Q000502:physiology*; D018118:Chloride Channels / Q000502:physiology*; D004285:Dogs; D005260:Female; D019254:Genes, bcl-2; D006801:Humans; D007668:Kidney; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics*; D011994:Recombinant Proteins / Q000378:metabolism; D014162:Transfection; D014407:Tumor Cells, Cultured; D002583:Uterine Cervical Neoplasms
D018118:Chloride Channels; D019253:Proto-Oncogene Proteins c-bcl-2; D011994:Recombinant Proteins; D002118:Calcium