Abstract
Most hematopoietic cells, such as thymocytes and lymphocytes, are known to be hypersensitive to radiation and exhibit interphase cell death with a typical morphological characteristic of apoptosis. In order to identify the signaling regulators associated with UV-induced apoptosis, we analyzed cellular proteins in Jurkat cells responding to UV irradiation using two dimensional gel electrophoresis (2DE).
Jurkat cells were irradiated with 20 J/m2 of UV, incubated for various time intervals, and then treated with digitonin for preparing their cytosolic extracts. Comparison of the high resolution 2DE protein patterns of the extracts from irradiated and un-irradiated cells showed differences in many spots including protein modifications. Intensive protein spots appeared in UV-irradiated cells were analyzed after tryptic digestion by peptide mass fingerprinting using a MALDI-TOF/TOF mass spectrometry. Interestingly, one of 12 proteins identified, acidic ribosomal protein P2 (P2) which is known to be mainly located within the 60s ribosomal subunit, was detected in three different pI spots, indicating the presence of two phosphorylation residues in cytoplasmic P2. Since only the phophorylated P2 was found in un-irradiated Jurkat cells and the amount of unphophorylated forms of P2 increased with increasing time of incubation after UV irradiation, the dephosphorylation of P2 may be associated with the activation of signaling pathways leading to apoptosis in UV-irradiated Jurkat cells.
