The cell-cycle regulatory protein p21cip1/waf1 is required for cytolethal distending toxin (Cdt)-induced apoptosis

Bruce J. Shenker, Lisa M. Walker, Ali Zekavat, Robert H. Weiss, Kathleen Boesze-Battaglia

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


The Aggregatibacter actinomycetemcomitans cytolethal distending toxin (Cdt) induces lymphocytes to undergo cell-cycle arrest and apoptosis; toxicity is dependent upon the active Cdt subunit, CdtB. We now demonstrate that p21CIP1/WAF1 is critical to Cdt-induced apoptosis. Cdt induces increases in the levels of p21CIP1/WAF1 in lymphoid cell lines, Jurkat and MyLa, and in primary human lymphocytes. These increases were dependent upon CdtB’s ability to function as a phosphatidylinositol (PI) 3,4,5-triphosphate (PIP3) phosphatase. It is noteworthy that Cdt-induced increases in the levels of p21CIP1/WAF1 were accompanied by a significant decline in the levels of phosphorylated p21CIP1/WAF1. The significance of Cdt-induced p21CIP1/WAF1 increase was assessed by preventing these changes with a two-pronged approach; pre-incubation with the novel p21CIP1/WAF1 inhibitor, UC2288, and development of a p21CIP1/WAF1-deficient cell line (Jurkatp21−) using clustered regularly interspaced short palindromic repeats (CRISPR)/cas9 gene editing. UC2288 blocked toxininduced increases in p21CIP1/WAF1, and JurkatWT cells treated with this inhibitor exhibited reduced suscepstibility to Cdt-induced apoptosis. Likewise, Jurkatp21− cells failed to undergo toxin-induced apoptosis. The linkage between Cdt, p21CIP1/WAF1, and apoptosis was further established by demonstrating that Cdt-induced increases in levels of the pro-apoptotic proteins Bid, Bax, and Bak were dependent upon p21CIP1/WAF1 as these changes were not observed in Jurkatp21− cells. Finally, we determined that the p21CIP1/WAF1 increases were dependent upon toxin-induced increases in the level and activity of the chaperone heat shock protein (HSP) 90. We propose that p21CIP1/WAF1 plays a key pro-apoptotic role in mediating Cdt-induced toxicity.

Original languageEnglish (US)
Article number38
Issue number1
StatePublished - Jan 2020


  • Aggregatibacter actinomycetemcomitans
  • Apoptosis
  • Cytolethal distending toxin
  • Lymphocytes
  • Virulence

ASJC Scopus subject areas

  • Immunology and Allergy
  • Molecular Biology
  • Immunology and Microbiology(all)
  • Microbiology (medical)
  • Infectious Diseases


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