Alterations of the actin polymerization status as an apoptotic morphological effector in HL-60 cells

Abstract

The alterations of the cytoskeletal actin network have been implicated as a morphological effector in apoptosis. However, studies directly linking actin change to the morphological events in apoptosis are lacking. This study quantitatively examined the effect of actin alteration on the camptothecin (CPT)-induced apoptotic process in HL-60 cells. Actin alteration was induced by two distinctive types of agent: the polymerization-stimulating agent, Jasplakinolide (Jas), and the polymerization-blocking agent, cytochalasin B (CB). The actin polymerization status was measured by two complementary methods: the cell pellet-based DNase I inhibition method, and the individual cell-based quantitative fluorescence image analysis (QFIA) assay. Actin polymerization induced by Jas caused apoptosis directly. By contrast, CB, an actin polymerization-blocking agent, partially inhibited CPT-induced apoptosis. A similar inhibition of the CPT-induced apoptosis response was observed with a more specific actin depolymerization agent, cytochalasin E. The alterations of the actin polymerization status occurred in three sequential steps during the apoptotic process: first polymerization, followed by depolymerization, and finally degradation. However, compared with CPT-induced apoptosis, Jas-induced apoptosis was characterized by pronounced actin polymerization that corresponded morphologically with prominent membrane blebbing, but less apoptotic body formation. Furthermore, DNase I activity, which is normally inhibited by G-actin, was specifically detected in Jas-treated cells. These results show that the regulation of actin polymerization is an important apoptotic morphological effector, whereas the alterations of the actin polymerization status by chemicals have profound effects not only on altering the morphology of apoptotic cells, but on apoptosis induction in HL-60 cells as well.

Endothelial Cellular Responses to Biodegradable Metal Zinc

“…The actin cytoskeleton was also involved in the apoptosis process, and alterations of actin polymerization had profound effects not only on apoptosis but also on cellular morphology. 45 The apoptotic process is accompanied by sequential cell morphology change, such as membrane blebbing, cell fragmentation, and apoptotic body formation. 45,46 Therefore, both actin polymerization alterations and cell morphology changes could be used as indicators for cell apoptosis.…”

“…45 The apoptotic process is accompanied by sequential cell morphology change, such as membrane blebbing, cell fragmentation, and apoptotic body formation. 45,46 Therefore, both actin polymerization alterations and cell morphology changes could be used as indicators for cell apoptosis. Since depolymerization of F-actin occurs during apoptosis, our findings suggested that 60 μM Zn 2+ could protect cells from apoptosis, while 140 μM Zn 2+ was likely to induce apoptosis.…”

The Plasma Membrane Potential and the Organization of the Actin Cytoskeleton of Epithelial Cells

“…Thus, interference with actin dynamics by inhibition of its depolymerization enhances apoptotic activity in HL-60 cells [170, 171]. However, in T-cells disruption of the actin cytoskeleton promotes caspase-3-mediated apoptosis [172].…”

Binding of Par-4 to the actin cytoskeleton is essential for Par-4/Dlk-mediated apoptosis

“…It is not yet clear, however, how the actin cytoskeleton is linked to the apoptotic machinery. For example, it has been demonstrated that actin polymerization is essential for the induction of apoptosis in endothelial cells [36] and in HL-60 cells [37,38]. On the other hand, in several other cell types, disruption of the cytoskeleton seems to trigger apoptosis [39][40][41].…”