Activated cofilin colocalises with Arp2/3 complex in apoptotic blebs during programmed cell death

Area of Science:

• Cell Biology
• Cancer Research
• Biochemistry

Background:

• Etoposide is a topoisomerase II inhibitor that induces apoptosis.
• Actin dynamics and associated proteins play roles in cellular processes, including cell death.

Purpose of the Study:

• To investigate the dynamic changes in actin, cofilin, and Arp2/3 complex localization during etoposide-induced apoptosis.
• To elucidate the role of these cytoskeletal components in the morphological changes associated with apoptosis.

Main Methods:

• Treatment of human epidermoid cancer cells (A431) and normal rat fibroblasts (NRK) with etoposide.
• Immunofluorescence microscopy to visualize actin, cofilin, and Arp2/3 complex.
• Analysis of cofilin phosphorylation status using immunoblots and 2D gel electrophoresis.
• EGFP-tagged cofilin constructs (wild-type, S3A, S3D mutants) for live-cell imaging.

Main Results:

• Etoposide induced significant apoptotic morphology, including nuclear and cytoplasmic fragmentation and blebbing.
• Actin and cofilin redistributed to membrane patches and apoptotic blebs, with actin being more peripheral.
• Active cofilin localized to apoptotic blebs and co-localized with actin.
• Arp2/3 complex was also found in apoptotic blebs.

Conclusions:

• Etoposide treatment alters the localization of actin, cofilin, and Arp2/3 during apoptosis.
• The active form of cofilin, along with actin and Arp2/3, is recruited to apoptotic blebs.
• These findings suggest a role for actin-based machinery in the formation of blebs during etoposide-induced cell death.