CAMK2D serves as a molecular scaffold for RNF8-MAD2 complex to induce mitotic checkpoint in glioma

Area of Science:

• Cell Biology
• Molecular Biology
• Cancer Research

Background:

• The spindle assembly checkpoint (SAC) protein MAD2 is crucial for preventing mitotic progression by forming the mitotic checkpoint complex.
• RNF8, a DNA damage response protein, has a poorly understood role in regulating the mitotic checkpoint.

Purpose of the Study:

• To elucidate the precise role of RNF8 in mitotic checkpoint regulation.
• To identify novel protein interactions and complexes involving RNF8 in cell cycle control.
• To explore the therapeutic potential of targeting the identified complex in gliomas.

Main Methods:

• Proximity proteomics to identify RNF8-interacting proteins.
• Biochemical assays to characterize protein-protein interactions (RNF8-MAD2, CAMK2D-RNF8).
• Functional assays in glioma stem cells (GSCs) to assess the impact of RNF8.
• Chemical biology approaches to identify inhibitors targeting the pathway.

Main Results:

• A novel CAMK2D-RNF8-MAD2 complex was identified, where RNF8 competes with p31^comet for MAD2 binding and CAMK2D acts as a scaffold.
• RNF8 overexpression impairs GSC mitotic progression in a manner dependent on its FHA and RING domains.
• Low RNF8 expression correlates with poor glioma patient outcomes, and RNF8 overexpression reduces GSC tumorigenicity.
• A PLK1 inhibitor mimics RNF8 overexpression effects; a PLK1/HSP90 inhibitor combination synergistically reduces GSC proliferation and stemness.

Conclusions:

• The study reveals a novel CAMK2D-RNF8-MAD2 complex critical for generating the mitotic checkpoint signal.
• This complex plays a significant role in regulating glioma stem cell proliferation and tumorigenicity.
• The identified pathway represents a potential therapeutic target for glioma treatment.