Ras-association domain family protein 6 induces apoptosis via both caspase-dependent and caspase-independent pathways.
The Ras-association domain family (RASSF) comprises six members (RASSF1-6) that each harbors a RalGDS/AF-6 (RA) and Sav/RASSF/Hippo (SARAH) domain. The RASSF proteins are known as putative tumor suppressors but RASSF6 has not yet been studied. We have here characterized human RASSF6. Although RASSF6 has RA domain, it does not bind Ki-Ras, Ha-Ras, N-Ras, M-Ras, or TC21 under the condition that Nore1 (RASSF5) binds these Ras proteins. The message of RASSF6 is detected by RT-PCR in several cell lines including HeLa, MCF-7, U373, A549, and HepG2 cells, but the protein expression is low. The enhanced expression of RASSF6 causes apoptosis in HeLa cells. RASSF6 activates Bax and induces cytochrome C release. Caspase-3 activation is also induced, but the caspase inhibitor, Z-VAD-FMK, does not block RASSF6-mediated apoptosis. Apoptosis-inducing factor and endonuclease G are released from the mitochondria upon expression of RASSF6 and their releases are not blocked by Z-VAD-FMK. The knock down of RASSF6 partially blocks tumor necrosis factor-alpha-induced cell death in HeLa cells. These findings indicate that RASSF6 is implicated in apoptosis in HeLa cells and that it triggers both caspase-dependent and caspase-independent pathways.
Ikeda
Mitsunobu
M
Department of Medical Biochemistry, Graduate School of Medicine, Rm D602, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8519, Japan.
Hirabayashi
Susumu
S
Fujiwara
Naoyuki
N
Mori
Hiroki
H
Kawata
Akira
A
Iida
Junko
J
Bao
Yijun
Y
Sato
Yuji
Y
Iida
Tadatsune
T
Sugimura
Haruhiko
H
Hata
Yutaka
Y
D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis; D051033:Apoptosis Inducing Factor / Q000378:metabolism; D051017:Apoptosis Regulatory Proteins; D019556:COS Cells; D053148:Caspase 3 / Q000378:metabolism; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism*; D016923:Cell Death; D002460:Cell Line; D002522:Chlorocebus aethiops; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D045304:Cytochromes c / Q000378:metabolism; D004706:Endodeoxyribonucleases / Q000378:metabolism; D004789:Enzyme Activation; D006367:HeLa Cells; D006801:Humans; D020559:Monomeric GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D015398:Signal Transduction; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D051028:bcl-2-Associated X Protein / Q000378:metabolism; D018631:ras Proteins / Q000378:metabolism
C494829:AIFM1 protein, human; D000590:Amino Acid Chloromethyl Ketones; D051033:Apoptosis Inducing Factor; D051017:Apoptosis Regulatory Proteins; D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors; C519911:RASSF6 protein, human; D014409:Tumor Necrosis Factor-alpha; D025521:Tumor Suppressor Proteins; D051028:bcl-2-Associated X Protein; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; D045304:Cytochromes c; D004706:Endodeoxyribonucleases; C052391:endonuclease G; D053148:Caspase 3; D020169:Caspases; D020559:Monomeric GTP-Binding Proteins; D018631:ras Proteins