Heat shock proteins and p53 play a critical role in K+ channel-mediated tumor cell proliferation and apoptosis.
Plasma membrane potassium (K+) channels are required for tumor cell proliferation and apoptosis. However, the signal transduction mechanisms underlying K+ channel-dependent tumor cell proliferation or apoptosis remains elusive. Using HeLa and A2780 cells as study models, we tested the hypothesis that apoptotic proteins are linked with K+ channel-dependent tumor cell cycle and apoptosis. The patch-clamping study using the whole-cell mode revealed two components of voltage-gated outward K+ currents: one is sensitive to either tetraethylammonium (TEA) or tetrandrine (Tet), a maxi-conductance Ca2+-activated K+ (BK) channel blocker, and the other is sensitive to 4-aminopyridine (4-AP), a delayed rectifier K+ channel blocker. MTT and flow cytometry assays showed that TEA, Tet, or iberiotoxin (Ibtx), a selective BK channel blocker, inhibited HeLa and A2780 cell proliferation in a dose-dependent manner with G1 phase arrest. Pretreatment with TEA or Tet also induced apoptosis in HeLa and A2780 cells. However, glibenclamide (Gli), an ATP-sensitive K+ channel blocker, did not influence K+ currents, proliferation or apoptosis. Western blot analyses showed that while pretreatment of TEA and Tet produced an increase in expressions of p53, p21, and Bax, pretreatment of these two agents led to a decrease in expressions of heat shock protein (hsp)90alpha, hsp90beta, and hsp70. Our results indicate that the blockade of BK channels results in tumor cell apoptosis and cycle arrest at G1 phase, and the transduction pathway underlying the anti-proliferative effects is linked to the increased expression of apoptotic protein p53 and the decreased expression of its chaperone proteins hsp.
Han
Xiaobing
X
Cancer Biology Reseach Center, Tongji Hospital, Huazhong University of Science and Technology, Wuhan, Hubei, 430030, China.
Wang
Fang
F
Yao
Weixing
W
Xing
Hui
H
Weng
Danhui
D
Song
Xiaohong
X
Chen
Gang
G
Xi
Ling
L
Zhu
Tao
T
Zhou
Jianfeng
J
Xu
Gang
G
Wang
Shixuan
S
Meng
Li
L
Iadecola
Costantino
C
Wang
Gang
G
Ma
Ding
D
D015761:4-Aminopyridine / Q000378:metabolism; D000470:Alkaloids / Q000378:metabolism; D017209:Apoptosis / Q000502:physiology*; D044182:Benzylisoquinolines / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000378:metabolism; D002453:Cell Cycle; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism; D053938:DNA Fragmentation; D004268:DNA-Binding Proteins / Q000378:metabolism; D005905:Glyburide / Q000378:metabolism; D006360:Heat-Shock Proteins / Q000378:metabolism*; D006801:Humans; D051036:Large-Conductance Calcium-Activated Potassium Channels / Q000378:metabolism*; D009369:Neoplasms / Q000378:metabolism / Q000473:pathology; D009856:Oncogene Proteins, Viral / Q000378:metabolism; D018408:Patch-Clamp Techniques; D010455:Peptides / Q000378:metabolism; D026902:Potassium Channel Blockers / Q000378:metabolism; D019789:Tetraethylammonium / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D051028:bcl-2-Associated X Protein / Q000378:metabolism
D000470:Alkaloids; D044182:Benzylisoquinolines; D002121:Calcium Channel Blockers; D050759:Cyclin-Dependent Kinase Inhibitor p21; D004268:DNA-Binding Proteins; C052603:E6 protein, Human papillomavirus type 18; D006360:Heat-Shock Proteins; D051036:Large-Conductance Calcium-Activated Potassium Channels; D009856:Oncogene Proteins, Viral; D010455:Peptides; D026902:Potassium Channel Blockers; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein; C009438:tetrandrine; D019789:Tetraethylammonium; C064719:iberiotoxin; D015761:4-Aminopyridine; D005905:Glyburide