PKCδ Regulates DNA Damage and Cell Death through a SIRT6/Nrf2-dependent Antioxidant Response

Area of Science:

• Cellular Biology
• Radiation Oncology
• Biochemistry

Background:

• Protein kinase C delta (PKCδ) plays a role in DNA repair and apoptosis.
• Inhibition of PKCδ has shown promise in providing radioprotection.
• Understanding the mechanisms behind PKCδ-mediated radioprotection is crucial for clinical applications.

Purpose of the Study:

• To investigate the role of PKCδ depletion in mitochondrial reactive oxygen species (ROS) production and the subsequent antioxidant response.
• To elucidate the signaling pathways, including Nrf2 and Sirtuin 6 (SIRT6), involved in PKCδ-regulated cellular responses to irradiation.
• To explore the potential of targeting the PKCδ/SIRT6 pathway for radioprotection.

Main Methods:

• PKCδ depletion using knockdown techniques.
• Measurement of mitochondrial ROS production, DNA damage, and cell death.
• Assessment of antioxidant response pathways, including Nrf2 activation.
• Analysis of electron transport chain (ETC) complex activity and mitochondrial function.
• Experimental validation using PKCδ/SIRT6 double knockdown cells and N-acetyl-L-cysteine treatment.

Main Results:

• PKCδ depletion increases mitochondrial ROS production and activates the endogenous antioxidant response via Nrf2.
• This leads to decreased basal and irradiation-induced DNA damage and cell death.
• Radioprotection is dependent on the antioxidant response and can be reversed by free radical scavengers.
• ETC dysfunction, specifically in Complex I and Complex III, is identified as the source of increased mitochondrial ROS.
• The PKCδ-regulated antioxidant response is mediated by SIRT6, with double knockdown reversing the observed effects.

Conclusions:

• PKCδ depletion triggers an endogenous antioxidant response, offering significant radioprotection.
• The PKCδ/SIRT6 signaling pathway is central to regulating DNA repair and cell death.
• Targeting this pathway presents a novel strategy for protecting healthy tissues during radiation therapy.