Lunatic fringe promotes the aggregation of CADASIL NOTCH3 mutant proteins

Area of Science:

• Neuroscience
• Genetics
• Molecular Biology

Background:

• Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a genetic small vessel disease.
• It is characterized by NOTCH3 mutations and abnormal NOTCH3 protein aggregation around vessel walls.
• NOTCH3 degradation by JAGGED1 (JAG1) via trans-endocytosis is crucial, with two mutation types: signal-active (SA) and signal-deficient (SD).

Purpose of the Study:

• To investigate the conditions leading to abnormal aggregation of NOTCH3 mutant proteins in CADASIL.
• To determine the role of JAGGED1 (JAG1) in the degradation and aggregation of different NOTCH3 mutant types.
• To explore the influence of lunatic fringe (LFNG) on NOTCH3 and its mutant aggregation.

Main Methods:

• Coculture assays were performed to study NOTCH3-JAG1 interactions.
• Sucrose gradient ultracentrifugation was used to assess protein aggregation.
• Analysis included wild-type (WT) NOTCH3, SA mutants (C49Y, R90C, R141C, C185R), and SD mutant (C428S).

Main Results:

• SA NOTCH3 mutants were degraded and trans-endocytosed by JAG1, similar to WT NOTCH3.
• The SD NOTCH3 mutant (C428S) was not degraded or endocytosed by JAG1.
• LFNG decreased WT NOTCH3 aggregation but increased C185R NOTCH3 aggregation.

Conclusions:

• SD NOTCH3 mutants may accumulate more than SA mutants upon JAG1 interaction.
• LFNG appears to promote the aggregation of SA NOTCH3 mutants.
• Environmental factors may be necessary for SA NOTCH3 mutant aggregation.