NLS-binding deficient Kapβ2 reduces neurotoxicity via selective interaction with C9orf72-ALS/FTD dipeptide repeats

Area of Science:

• Neuroscience
• Molecular Biology
• Biochemistry

Background:

• Arginine-rich dipeptide repeat proteins (R-DPRs) are toxic culprits in C9orf72-linked amyotrophic lateral sclerosis and frontotemporal dementia (C9-ALS/FTD).
• R-DPRs induce cellular damage by interfering with the phase behavior of RNA-binding proteins (RBPs).

Purpose of the Study:

• To investigate the mechanism of R-DPR-induced aberrant RBP phase transition using FUS as a model RBP.
• To develop a therapeutic strategy using Kapβ2 that selectively targets R-DPRs without affecting native RBP functions.

Main Methods:

• Utilized FUS as a model RNA-binding protein to study R-DPR interactions.
• Engineered a nuclear localization signal (NLS)-binding deficient Kapβ2 mutant (Kapβ2_W460A:W730A).
• Assessed the selective binding of Kapβ2_W460A:W730A to R-DPRs and its effect on FUS phase separation and stress granule formation.

Main Results:

• Wild-type Kapβ2 mitigates R-DPR-induced phase transition but may cause off-target effects on native RBPs.
• Kapβ2_W460A:W730A selectively interacts with R-DPRs without disrupting normal FUS phase separation.
• Kapβ2_W460A:W730A prevents poly(GR) enrichment in stress granules and reduces R-DPR neurotoxicity.

Conclusions:

• A modified Kapβ2 protein (Kapβ2_W460A:W730A) demonstrates selective targeting of toxic R-DPRs.
• This selective targeting mitigates R-DPR-induced neurotoxicity, presenting a promising therapeutic avenue for C9-ALS/FTD.