Granulocyte-Macrophage Colony-Stimulating Factor Rescues TF-1 Leukemia Cells From Ionizing Radiation-Induced Apoptosis Through a Pathway Mediated by Protein Kinase Cα

Abstract

Protein kinase C (PKC) activity has a recognized role in mediating apoptosis. However, the role of individual PKC isoforms in apoptosis is poorly defined. Therefore, we investigated the translocation of individual PKC isoforms during radiation-induced apoptosis with and without rescue from apoptosis by granulocyte-macrophage colony-stimulating factor (GM-CSF) in the human erythroleukemia cell line TF-1. PKCα was translocated from the particulate to cytosolic fraction of TF-1 cells within 5 minutes of treatment with apoptosis-inducing levels of ionizing radiation. However, this postirradiation translocation did not occur when cells were rescued from apoptosis by GM-CSF. Furthermore, treatment of cells with Gö6976, an inhibitor of classical PKC isoforms, abrogated the rescue effect of GM-CSF. The calcium-independent novel PKC isoform, PKCδ appeared to be degraded in both the particulate and cytosolic fractions of TF-1 cells after treatment with apoptosis-inducing levels of ionizing radiation in either the presence or absence of GM-CSF rescue. Levels of ceramide, a lipid mediator of apoptosis, were measured at 2, 4, 8, 10, and 60 minutes after treatment with ionizing radiation and were substantially reduced in TF-1 cells rescued from apoptosis by GM-CSF compared with apoptotic TF-1 cells. The largest decrease in ceramide production seen was at 4 minutes postirradiation, with a 46% reduction in ceramide levels in TF-1 cells rescued from apoptosis by GM-CSF compared with those in apoptotic TF-1 cells. Because ceramide has been shown to affect PKCα subcellular distribution, these data implicate a role for ceramide in mediating the rapid postirradiation translocation and inhibition of PKCα in TF-1 cells not rescued from apoptosis by GM-CSF. Expression of the antiapoptotic protein Bcl-2 doubled in TF-1 cells rescued from apoptosis by GM-CSF, but did not increase in unrescued cells. Our findings suggest that activated PKCα and increased expression of Bcl-2 after γ irradiation determine survival in TF-1 cells rescued from apoptosis with GM-CSF and that PKCδ plays a role in mediating signals involved in sensing cellular damage and/or regulation of cell damage repair.

Inhibition of ubiquitin-proteasome pathway activates a caspase-3-like protease and induces Bcl-2 cleavage in human M-07e leukaemic cells

“…Using transfected cells overexpressing caspase 3, Cheng et al [22] showed that Bcl-2 can be transformed into a Bax-like death-effector by cleavage of caspase 3 during apoptosis induced by Fas ligation and interleukin 3 depletion. In contrast, no Bcl-2 cleavage was detected in GM-CSF-dependent TF-1 leukaemic cells induced to undergo apoptosis by ionizing radiation [23]. Therefore the occurrence of Bcl-2 cleavage might depend primarily on the degree of caspase 3 activation and the levels of Bcl-2 in the cells, both of which are expressed abundantly in M-07e cells.…”

Granulocyte-macrophage colony-stimulating factor protects dendritic cells from liposome-encapsulated dichloromethylene diphosphonate-induced apoptosis through a Bcl-2-mediated pathway

“…In this context, survival signals of GM-CSF have been described in other cellular systems. This cytokine has been recently shown to protect TF-1 leukemia cells from ionizing radiation-induced apoptosis through a pathway mediated by protein kinase C § [30]. Furthermore, this cytokine confers resistance to polymorphonuclear leukocytes from UV-induced apoptosis [31].…”

Short-term delay of Fas-stimulated apoptosis by GM-CSF as a result of temporary suppression of FADD recruitment in neutrophils: evidence implicating phosphatidylinositol 3-kinase and MEK1-ERK1/2 pathways downstream of classical protein kinase C

“…PI-3K and MEK1-ERK1/2 pathways are activated downstream of PKCs in GM-CSF-treated neutrophils and mediate FADD modifications and impaired FADD recruitment to Fas Despite previous reports in other cell types that GM-CSF has antiapoptotic actions through PKC␣ [37], mediator(s) downstream of this classical PKC remained to be determined. PKCs are a family of serine/threonine protein kinases composed of at least 12 isozymes.…”