Programmed cell death (apoptosis) is induced rapidly and with positive cooperativity by activation of cyclic adenosine monophosphate‐kinase I in a myeloid leukemia cell line

Abstract

Programmed death (apoptosis) of the rat myelocytic leukemic cell line IPC-81 was triggered by cyclic adenosine monophosphate (cAMP) analogs or by agents (cholera toxin, prostaglandins) increasing the endogenous cAMP level. The induction of cell death by cholera toxin was preceded by increased activation of cAMP-kinase. Cell lysis started already 5 hr after cAMP challenge and was preceded by internucleosomal DNA fragmentation and morphological changes characteristic of apoptosis. The cell suicide could be prevented by inhibitors of macromolecular synthesis. cAMP analogs induced cell death in a positively cooperative manner (apparent Hill coefficient of 2.9), indicating that triggering of the apoptotic process was under stringent control. There was a strong synergism between cAMP analogs complementing each other in the activation of cAMP-dependent protein kinase I (cAKI). No such synergism was noted for analogs complementing each other in the activation of cAKII. It is concluded that apoptosis can be induced solely by activation of cAKI. The IPC-81 cells expressed about four times more cAKI than cAKII. The expression of cAK subunits, on the protein and mRNA levels, was only minimally affected by cholera toxin treatment.

The transcriptional repressor ICER and cAMP-induced programmed cell death

“…Furthermore, cell death is delayed by treating IPC-81 cells with actinomycin D or cycloheximide. This treatment suppresses morphological changes typical of apoptosis, as well as DNA fragmentation and 28S rRNA cleavage (Lanotte et al, 1991;Houge et al, 1993Houge et al, , 1995. This suggest a direct involvement of PKA-directed gene expression.…”

“…We have previously shown that agonistic stimulation of adenylate cyclase coupled membrane receptors or treatment with cholera toxin and cAMP analogues induce IPC-81 cells to undergo apoptosis (Lanotte et al, 1991).…”

“…Prostaglandin E1 (PGE 1 ) treatment of IPC-81 cells causes a dramatic morphological change which is reminiscent of cAMPinduced cell death ( Figure 1a,b); and in Lanotte et al, 1991). Cells treated with PGE1 show high sensitivity with an IC 50 of 0.2 mM (Figure 1c).…”

“…Signal transduction pathways appear to play a key role in apoptosis. The second messengers Ca 2+ , cAMP and phorbol esters which activate protein kinases such as calmodulin kinase, PKA, PKC and also tyrosine kinases (Pratt and Martin, 1975;Kizaki et al, 1989Kizaki et al, , 1990McConkey et al, 1990;Susuki et al, 1990;Lanotte et al, 1991;Dowd and Miesfeld, 1992) have all been implicated in apoptotic processes. The mechanisms whereby signalling pathways direct apoptosis appear to be complex and cell type-speci®c.…”

“…The IPC-81 cell line , derived from a rat myeloid leukaemia so far represents one of the bestde®ned cell systems to study cAMP-induced apoptosis. We have previously demonstrated that treatment with agents elevating intracellular cAMP levels (cholera toxin, prostaglandins (PGEs), IBMX and cAMPanalogues) rapidly induces IPC-81 cell death (Lanotte et al, 1991). More than 90% of the cells show morphological changes and internucleosomal DNA fragmentation typical of apoptosis within 6 h of induction.…”