The RIP1/RIP3 necrosome forms a functional amyloid signaling complex required for programmed necrosis
Jixi Li1, Thomas McQuade, Ansgar B Siemer
1Department of Biochemistry, Weill Cornell Medical College, New York, NY 10065, USA.
Cell
|July 24, 2012
Summary
RIP1 and RIP3 kinases form amyloid fibrils that drive programmed necrosis. Inhibiting these amyloid structures with dyes like Thioflavin T partially blocks necrosis, revealing a new signaling mechanism.
Area of Science:
- Biochemistry
- Cell Biology
- Structural Biology
Background:
- Tumor Necrosis Factor (TNF)-induced programmed necrosis involves RIP1 and RIP3 kinases.
- The precise structural mechanisms governing RIP kinase signaling remain incompletely understood.
Purpose of the Study:
- To investigate the structural basis of RIP1 and RIP3 kinase complex formation.
- To determine the role of RIP homotypic interaction motifs (RHIMs) in kinase assembly and signaling.
- To explore the potential involvement of amyloid structures in programmed necrosis.
Main Methods:
- Biophysical techniques including Thioflavin T (ThT) and Congo red (CR) binding assays, circular dichroism, infrared spectroscopy, X-ray diffraction, and solid-state NMR.
- Analysis of RIP1 and RIP3 RHIM mutants.
- Isolation and characterization of endogenous RIP1/RIP3 complexes from necrotic cells.
- In vivo studies of programmed necrosis.
Main Results:
- RIP1 and RIP3 RHIMs mediate the formation of heterodimeric amyloid fibrils.
- These fibrils possess structured amyloid cores with flanking mobile regions.
- Endogenous RIP1/RIP3 complexes exhibit amyloid characteristics and are ultrastable.
- Amyloid dyes (ThT, CR, HBX) partially inhibit programmed necrosis.
- RHIM mutations disrupt kinase complex formation, activation, and programmed necrosis.
Conclusions:
- RIP kinases assemble into amyloid structures that are critical for programmed necrosis.
- Amyloid formation is a key structural event in RIP kinase-mediated signaling.
- This work expands the known functions of amyloids to cellular signaling complexes.
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