Open AccessRegulation of apoptosis by the p8/prothymosin α complex
Author(s) -
Cédric Malicet,
Valentin Giroux,
Sophie Vasseur,
Jean Charles Dagorn,
José L. Neira,
Juan Iovanna
Publication year - 2006
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.0508955103
Subject(s) - staurosporine , hela , apoptosis , microbiology and biotechnology , caspase , small interfering rna , biology , caspase 3 , chemistry , programmed cell death , transfection , signal transduction , biochemistry , cell , gene , protein kinase c
p8 is a small-stress protein involved in several cellular functions including apoptosis. To identify its putative partners, we screened a HeLa cDNA library by using the two-hybrid technique and found that p8 binds the antiapoptotic protein prothymosin α (ProTα). Fluorescence spectroscopy, circular dichroism, and NMR spectroscopy showed that p8 and ProTα formed a complex. Binding resulted in important changes in the secondary and tertiary structures of the proteins. Because p8 and ProTα form a complex, they could act in concert to regulate the apoptotic cascade. We induced apoptosis in HeLa cells by staurosporine treatment and monitored the effects of knocking down p8 and/or ProTα or overexpressing p8 and/or ProTα on caspase 3/7 and 9 activities and on cell death. Transfecting ProTα or p8 small interfering RNAs increased the activities of both caspases and the number of apoptotic nuclei. However, transfecting both small interfering RNAs resulted in no further increase. Overexpressing p8 or ProTα did not alter caspase activities, whereas overexpressing both resulted in a significant reduction of caspase activities. These results strongly suggest that the antiapoptotic response of HeLa cells upon staurosporine treatment requires expression of both p8 and ProTα.