HSP70 inhibits stress-induced cardiomyocyte apoptosis by competitively binding to FAF1.
Stress-induced cardiomyocyte apoptosis plays an important role in the pathogenesis of a variety of cardiovascular diseases. Our early studies showed that HSP70 effectively inhibited apoptosis, but the underlying mechanism remained unclear. Fas-associated factor 1 (FAF1) is a member of the Fas death-inducing signaling complex (Fas-DISC) that acts upstream of caspase-8. We investigated the interactions among FAF1, HSP70, and FAS in stressed cardiomyocytes to elucidate the protective mechanism of HSP70. FAS and caspase-3/8 activity was higher in cardiomyocytes undergoing stress-induced apoptosis in restraint-stressed rats compared with cardiomyocytes in non-stressed rats, which indicated that the Fas signaling pathway was activated after restraint stress. Geranylgeranylacetone (GGA) induced an increase in HSP70 expression, which reduced stress-induced apoptosis. Additionally, overexpression of HSP70 via transfection with the pEGFP-rHSP70 plasmid attenuated norepinephrine (NE)-induced apoptosis. FAF1 expression increased during stress-induced apoptosis, and overexpression of FAF1 exacerbated NE-induced apoptosis. We also found that HSP70 interacted with FAF1. Overexpression of HSP70 inhibited the binding of FAF1 to FAS in H9C2 cells, which indicated that HSP70 suppressed NE-induced apoptosis by competitively binding to FAF1. An N-terminal deletion mutant of HSP70 (HSP70-△N) was unable to interact with FAF1. After HSP70-△N was transfected into H9C2 cells, the cells were unable to attenuate the NE-induced increases in caspase-8 and apoptosis. These results indicate that the 1-120 sequence of HSP70 binds to FAF1, which alters the interactions between FAS and FAF1 and inhibits the activation of the Fas signaling pathway and apoptosis.
Institute of Basic Medical Sciences, No. 27 Taiping Road, Haidian District, Beijing, 100850, China.
Xiujie
X
Gao
Weili
W
Liu
Lishuang
L
Huang
Tao
T
Zhang
Zhusong
Z
Mei
Xinxing
X
Wang
Jingbo
J
Gong
Yun
Y
Zhao
Fang
F
Xie
Jing
J
Ma
Lingjia
L
Qian
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D004224:Diterpenes / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D008297:Male; D032383:Myocytes, Cardiac / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D009638:Norepinephrine / Q000097:blood / Q000494:pharmacology; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction / Q000187:drug effects; D013312:Stress, Physiological
D002352:Carrier Proteins; D004224:Diterpenes; D018840:HSP70 Heat-Shock Proteins; C031049:geranylgeranylacetone; D009638:Norepinephrine