Apoptosis-related fragmentation, translocation, and properties of human prothymosin alpha

• Published in: Experimental cell research Vol. 284; no. 2; pp. 209 - 221
• Main Authors: Evstafieva, Alexandra G, Belov, George A, Rubtsov, Yuri P, Kalkum, Markus, Joseph, Bertrand, Chichkova, Nina V, Sukhacheva, Elena A, Bogdanov, Alexey A, Pettersson, Ralf F, Agol, Vadim I, Vartapetian, Andrey B
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.04.2003
• Subjects: Active Transport, Cell Nucleus - drug effects; Active Transport, Cell Nucleus - physiology; Amino Acid Sequence - physiology; Antibodies, Monoclonal; Apoptosis; Apoptosis - drug effects; Apoptosis - physiology; Caspase 3; Caspases - metabolism; Cell Membrane - drug effects; Cell Membrane - metabolism; Cell Nucleus - drug effects; Cell Nucleus - metabolism; Cytoplasm - drug effects; Cytoplasm - metabolism; Eukaryotic Cells - metabolism; Exocytosis - drug effects; Exocytosis - physiology; HeLa Cells; Humans; Intracellular trafficking; Medicin och hälsovetenskap; Mutation - genetics; Peptide Fragments - metabolism; Protein Precursors - antagonists & inhibitors; Protein Precursors - biosynthesis; Protein Precursors - genetics; Protein Structure, Tertiary - drug effects; Protein Structure, Tertiary - physiology; Protein Transport - drug effects; Protein Transport - physiology; Prothymosin α; Surface exposure; Thymosin - analogs & derivatives; Thymosin - antagonists & inhibitors; Thymosin - biosynthesis; Thymosin - genetics; Surface exposure; Caspase-3; Intracellular trafficking; Apoptosis; Prothymosin α
• ISSN: 0014-4827; 1090-2422
• DOI: 10.1016/S0014-4827(02)00047-2

Human prothymosin α is a proliferation-related nuclear protein undergoing caspase-mediated fragmentation in apoptotic cells. We show here that caspase-3 is the principal executor of prothymosin α fragmentation in vivo. In apoptotic HeLa cells as well as in vitro, caspase-3 cleaves prothymosin α at one major carboxy terminal (DDVD 99) and several suboptimal sites. Prothymosin α cleavage at two amino-terminal sites (AAVD 6 and NGRD 31) contributes significantly to the final pattern of prothymosin α fragmentation in vitro and could be detected to occur in apoptotic cells. The major caspase cleavage at D 99 disrupts the nuclear localization signal of prothymosin α, which leads to a profound alteration in subcellular localization of the truncated protein. By using a set of anti-prothymosin α monoclonal antibodies, we were able to observe nuclear escape and cell surface exposure of endogenous prothymosin α in apoptotic, but not in normal, cells. We demonstrate also that ectopic production of human prothymosin α and its mutants with nuclear or nuclear-cytoplasmic localization confers increased resistance of HeLa cells toward the tumor necrosis factor-induced apoptosis.