Caspase-mediated cleavage of HuR in the cytoplasm contributes to pp32/PHAP-I regulation of apoptosis.
The RNA-binding protein HuR affects cell fate by regulating the stability and/or the translation of messenger RNAs that encode cell stress response proteins. In this study, we delineate a novel regulatory mechanism by which HuR contributes to stress-induced cell death. Upon lethal stress, HuR translocates into the cytoplasm by a mechanism involving its association with the apoptosome activator pp32/PHAP-I. Depleting the expression of pp32/PHAP-I by RNA interference reduces both HuR cytoplasmic accumulation and the efficiency of caspase activation. In the cytoplasm, HuR undergoes caspase-mediated cleavage at aspartate 226. This cleavage activity is significantly reduced in the absence of pp32/PHAP-I. Substituting aspartate 226 with an alanine creates a noncleavable isoform of HuR that, when overexpressed, maintains its association with pp32/PHAP-I and delays the apoptotic response. Thus, we propose a model in which HuR association with pp32/PHAP-I and its caspase-mediated cleavage constitutes a regulatory step that contributes to an amplified apoptotic response.
Mazroui
Rachid
R
Department of Biochemistry, McGill University Health Center, McGill University, Montreal, Quebec H3G 146, Canada.
Di Marco
Sergio
S
Clair
Eveline
E
von Roretz
Christopher
C
Tenenbaum
Scott A
SA
Keene
Jack D
JD
Saleh
Maya
M
Gallouzi
Imed-Eddine
IE
D000954:Antigens, Surface / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017209:Apoptosis / Q000187:drug effects; D053478:Apoptosomes / Q000502:physiology; D001665:Binding Sites; D020169:Caspases / Q000378:metabolism*; D051959:ELAV Proteins; D000067780:ELAV-Like Protein 1; D004789:Enzyme Activation; D006367:HeLa Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism / Q000502:physiology*; D008954:Models, Biological; D016297:Mutagenesis, Site-Directed; D009687:Nuclear Proteins / Q000378:metabolism / Q000502:physiology*; D010750:Phosphoproteins / Q000378:metabolism / Q000502:physiology; D020033:Protein Isoforms / Q000378:metabolism; D017434:Protein Structure, Tertiary; D034622:RNA Interference; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D019311:Staurosporine / Q000494:pharmacology
C087425:ANP32A protein, human; D000954:Antigens, Surface; D053478:Apoptosomes; D051959:ELAV Proteins; D000067780:ELAV-Like Protein 1; C098770:ELAVL1 protein, human; D047908:Intracellular Signaling Peptides and Proteins; D009687:Nuclear Proteins; D010750:Phosphoproteins; D020033:Protein Isoforms; D016601:RNA-Binding Proteins; D020169:Caspases; D019311:Staurosporine