Specific ablation of the apoptotic functions of cytochrome C reveals a differential requirement for cytochrome C and Apaf-1 in apoptosis.
As components of the apoptosome, a caspase-activating complex, cytochrome c (Cyt c) and Apaf-1 are thought to play critical roles during apoptosis. Due to the obligate function of Cyt c in electron transport, its requirement for apoptosis in animals has been difficult to establish. We generated "knockin" mice expressing a mutant Cyt c (KA allele), which retains normal electron transfer function but fails to activate Apaf-1. Most KA/KA mice displayed embryonic or perinatal lethality caused by defects in the central nervous system, and surviving mice exhibited impaired lymphocyte homeostasis. Although fibroblasts from the KA/KA mice were resistant to apoptosis, their thymocytes were markedly more sensitive to death stimuli than Apaf-1(-/-) thymocytes. Upon treatment with gamma irradiation, procaspases were efficiently activated in apoptotic KA/KA thymocytes, but Apaf-1 oligomerization was not observed. These studies indicate the existence of a Cyt c- and apoptosome-independent but Apaf-1-dependent mechanism(s) for caspase activation.
Hao
Zhenyue
Z
The Campbell Family Institute for Breast Cancer Research, University Health Network, University of Toronto, Toronto, Ontario M5G 2C1, Canada; Ontario Cancer Institute, University Health Network, University of Toronto, Toronto, Ontario M5G 2C1, Canada; Departments of Immunology and Medical Biophysics, University of Toronto, Toronto, Ontario M5G 2C1, Canada. Electronic address: zyhao@uhnres.utoronto.ca.
Duncan
Gordon S
GS
The Campbell Family Institute for Breast Cancer Research, University Health Network, University of Toronto, Toronto, Ontario M5G 2C1, Canada; Ontario Cancer Institute, University Health Network, University of Toronto, Toronto, Ontario M5G 2C1, Canada; Departments of Immunology and Medical Biophysics, University of Toronto, Toronto, Ontario M5G 2C1, Canada.
Chang
Chia-Che
CC
The Campbell Family Institute for Breast Cancer Research, University Health Network, University of Toronto, Toronto, Ontario M5G 2C1, Canada; Ontario Cancer Institute, University Health Network, University of Toronto, Toronto, Ontario M5G 2C1, Canada; Departments of Immunology and Medical Biophysics, University of Toronto, Toronto, Ontario M5G 2C1, Canada.
Elia
Andrew
A
The Campbell Family Institute for Breast Cancer Research, University Health Network, University of Toronto, Toronto, Ontario M5G 2C1, Canada; Ontario Cancer Institute, University Health Network, University of Toronto, Toronto, Ontario M5G 2C1, Canada; Departments of Immunology and Medical Biophysics, University of Toronto, Toronto, Ontario M5G 2C1, Canada.
Fang
Min
M
Howard Hughes Medical Institute and Department of Biochemistry, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390.
Wakeham
Andrew
A
The Campbell Family Institute for Breast Cancer Research, University Health Network, University of Toronto, Toronto, Ontario M5G 2C1, Canada; Ontario Cancer Institute, University Health Network, University of Toronto, Toronto, Ontario M5G 2C1, Canada; Departments of Immunology and Medical Biophysics, University of Toronto, Toronto, Ontario M5G 2C1, Canada.
Okada
Hitoshi
H
The Campbell Family Institute for Breast Cancer Research, University Health Network, University of Toronto, Toronto, Ontario M5G 2C1, Canada; Ontario Cancer Institute, University Health Network, University of Toronto, Toronto, Ontario M5G 2C1, Canada; Departments of Immunology and Medical Biophysics, University of Toronto, Toronto, Ontario M5G 2C1, Canada.
Calzascia
Thomas
T
The Campbell Family Institute for Breast Cancer Research, University Health Network, University of Toronto, Toronto, Ontario M5G 2C1, Canada; Ontario Cancer Institute, University Health Network, University of Toronto, Toronto, Ontario M5G 2C1, Canada; Departments of Immunology and Medical Biophysics, University of Toronto, Toronto, Ontario M5G 2C1, Canada.
Jang
YingJu
Y
The Campbell Family Institute for Breast Cancer Research, University Health Network, University of Toronto, Toronto, Ontario M5G 2C1, Canada; Ontario Cancer Institute, University Health Network, University of Toronto, Toronto, Ontario M5G 2C1, Canada; Departments of Immunology and Medical Biophysics, University of Toronto, Toronto, Ontario M5G 2C1, Canada.
You-Ten
Annick
A
The Campbell Family Institute for Breast Cancer Research, University Health Network, University of Toronto, Toronto, Ontario M5G 2C1, Canada; Ontario Cancer Institute, University Health Network, University of Toronto, Toronto, Ontario M5G 2C1, Canada; Departments of Immunology and Medical Biophysics, University of Toronto, Toronto, Ontario M5G 2C1, Canada.
Yeh
Wen-Chen
WC
The Campbell Family Institute for Breast Cancer Research, University Health Network, University of Toronto, Toronto, Ontario M5G 2C1, Canada; Ontario Cancer Institute, University Health Network, University of Toronto, Toronto, Ontario M5G 2C1, Canada; Departments of Immunology and Medical Biophysics, University of Toronto, Toronto, Ontario M5G 2C1, Canada.
Ohashi
Pamela
P
The Campbell Family Institute for Breast Cancer Research, University Health Network, University of Toronto, Toronto, Ontario M5G 2C1, Canada; Ontario Cancer Institute, University Health Network, University of Toronto, Toronto, Ontario M5G 2C1, Canada; Departments of Immunology and Medical Biophysics, University of Toronto, Toronto, Ontario M5G 2C1, Canada.
Wang
Xiaodong
X
Howard Hughes Medical Institute and Department of Biochemistry, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390.
Mak
Tak W
TW
The Campbell Family Institute for Breast Cancer Research, University Health Network, University of Toronto, Toronto, Ontario M5G 2C1, Canada; Ontario Cancer Institute, University Health Network, University of Toronto, Toronto, Ontario M5G 2C1, Canada; Departments of Immunology and Medical Biophysics, University of Toronto, Toronto, Ontario M5G 2C1, Canada. Electronic address: tmak@uhnres.utoronto.ca.
D000818:Animals; D017209:Apoptosis / Q000502:physiology* / Q000528:radiation effects; D053477:Apoptotic Protease-Activating Factor 1; D020170:Caspase 1; D020169:Caspases / Q000378:metabolism* / Q000528:radiation effects; D045304:Cytochromes c / Q000235:genetics*; D004579:Electron Transport / Q000502:physiology / Q000528:radiation effects; D004789:Enzyme Activation / Q000502:physiology* / Q000528:radiation effects; D004792:Enzyme Precursors / Q000378:metabolism / Q000528:radiation effects; D005720:Gamma Rays; D008213:Lymphocyte Activation / Q000235:genetics; D051379:Mice; D018345:Mice, Knockout; D008817:Mice, Mutant Strains; D008822:Mice, Transgenic; D009421:Nervous System Malformations / Q000235:genetics / Q000378:metabolism; D011506:Proteins / Q000378:metabolism*; D013601:T-Lymphocytes / Q000378:metabolism
C506593:Apaf1 protein, mouse; D053477:Apoptotic Protease-Activating Factor 1; D004792:Enzyme Precursors; D011506:Proteins; D045304:Cytochromes c; D020169:Caspases; D020170:Caspase 1