Skip to main content
Protein phosphorylation associated with epipodophyllotoxin-induced apoptosis of lymphoid cells: Role of a serine/threonine protein kinase
Clinical immunology and immunopathology
  • Xiaodan Ye
  • Neeta S. Mody
  • Susan T. Hingley, Philadelphia College of Osteopathic Medicine
  • Frederick D. Coffman
  • Stanley Cohen
  • Kerin Fresa
Document Type
Publication Date
We have previously shown that apoptosis induced in thymocytes by dexamethasone or teniposide (VM-26) could be inhibited by 1-(5- isoquinolinylsulfonyl)-2-methylpiperazine (H7) and sangivamycin, both relatively specific inhibitors for protein kinase C, but not by N-(2- guanidinoethyl)-5-isoquinolinesulfonamide (HA1004), a more specific inhibitor for cAMP-dependent protein kinases. Apoptosis in this model system was not blocked by EGTA and no increase in cytosolic Ca2+ was observed during apoptosis induced by either dexamethasone or VM-26, suggesting that this kinase was Ca2+-independent. In the present study, we demonstrate that addition of 10 µM sangivamycin to thymocyte cultures up to 2 h after addition of either inducer resulted in virtually complete inhibition of apoptosis. Addition of 10 µM sangivamycin at 3 or 4 h after addition of inducer resulted in partial inhibition of apoptosis. Computerized image analysis of two-dimensional PAGE analyses of whole-cell lysates demonstrated that treatment of mouse thymocytes with VM-26 resulted in a limited number of de novo phosphorylation events within 1 h of treatment. The most prominent phosphorylation events associated with VM-26-induced apoptosis were that two intracellular protein species (Protein 1: m.w. = 22.9 kDa, pI, 5.11; and Protein 2: m.w. = 22.9 kDa, pI, 4.98). Similar phosphorylation events were seen in cells treated with dexamethasone. Finally, Western blot analysis suggests that de novo protein phosphorylation induced by VM-26 is on serine/threonine residues. These results provide further evidence that the mechanism of VM-26-induced apoptosis of murine thymocytes involves the action of one or more serine/threonine kinases.

This article was published in Clinical immunology and immunopathology, Volume 89, Issue 2, Pages 117-125.

The published version is available at

Copyright © 1998 Elsevier.

Citation Information
Xiaodan Ye, Neeta S. Mody, Susan T. Hingley, Frederick D. Coffman, et al.. "Protein phosphorylation associated with epipodophyllotoxin-induced apoptosis of lymphoid cells: Role of a serine/threonine protein kinase" Clinical immunology and immunopathology Vol. 89 (1998) p. 117 - 125
Available at: