A missense variant in SHARPIN mediates Alzheimer’s disease-specific brain damages

Abstract

Established genetic risk factors for Alzheimer’s disease (AD) account for only a portion of AD heritability. The aim of this study was to identify novel associations between genetic variants and AD-specific brain atrophy. We conducted genome-wide association studies for brain magnetic resonance imaging measures of hippocampal volume and entorhinal cortical thickness in 2643 Koreans meeting the clinical criteria for AD (n = 209), mild cognitive impairment (n = 1449) or normal cognition (n = 985). A missense variant, rs77359862 (R274W), in the SHANK-associated RH Domain Interactor (SHARPIN) gene was associated with entorhinal cortical thickness (p = 5.0 × 10−9) and hippocampal volume (p = 5.1 × 10−12). It revealed an increased risk of developing AD in the mediation analyses. This variant was also associated with amyloid-β accumulation (p = 0.03) and measures of memory (p = 1.0 × 10−4) and executive function (p = 0.04). We also found significant association of other SHARPIN variants with hippocampal volume in the Alzheimer’s Disease Neuroimaging Initiative (rs3417062, p = 4.1 × 10−6) and AddNeuroMed (rs138412600, p = 5.9 × 10−5) cohorts. Further, molecular dynamics simulations and co-immunoprecipitation indicated that the variant significantly reduced the binding of linear ubiquitination assembly complex proteins, SHPARIN and HOIL-1 Interacting Protein (HOIP), altering the downstream NF-κB signaling pathway. These findings suggest that SHARPIN plays an important role in the pathogenesis of AD.

Involvement of heterologous ubiquitination including linear ubiquitination in Alzheimer’s disease and amyotrophic lateral sclerosis

“…Among them, the G186R and R274W variants of SHARPIN reportedly suppressed TNF-α-mediated NF-κB activation and generated aberrant granular clumps in HEK293T cells ( Asanomi et al, 2019 ; Asanomi et al, 2022 ). Moreover, the R274W variant of SHARPIN shows a weaker interaction with HOIP ( Park et al, 2021 ). As an etiology of AD, SHARPIN reportedly regulates Aβ phagocytosis, inflammation, and cell death in macrophages by linking to the NLRP3 inflammasome in response to Aβ ( Krishnan et al, 2020 ).…”

“…In the crystal structure, the electron density of R274 of SHARPIN was unclear, and its side chain did not form hydrogen bonds or salt bridges with HOIP UBA1. However, a molecular dynamics (MD) simulation suggested that SHARPIN R274 forms hydrogen bonds and salt bridges with E487 and Q490 of HOIP, and the R274W mutation destabilizes the complex at the interface ( Park et al, 2021 ). This simulation was validated by co-immunoprecipitation assays, which showed that the binding between SHARPIN UBL (R274W) and HOIP UBA1-UBA2 was significantly reduced, as compared with that of SHARPIN UBL WT ( Park et al, 2021 ).…”

“…The R274W, D291G, and P294S SNPs are located in the SHARPIN UBL domain ( Figures 2A, B ) ( de Rojas et al, 2021 ; Park et al, 2021 ; Asanomi et al, 2022 ). The crystal structure of the human SHARPIN UBL in complex with the human HOIP UBA1-UBA2 revealed that the SHARPIN UBL mainly interacts with the N-terminal helix of HOIP UBA1 ( Figure 3D ) ( Liu et al, 2017 ).…”

NF-κB in neurodegenerative diseases: Recent evidence from human genetics

“…Recent genetic evidence of potential loss-of-function mutants involved in NF-κB signaling of AD patients might provide a genetic reason for this early correlation ( Bellenguez et al, 2022 ). In this line, human SHARPIN mutants were shown to have less capability of NF-κB activation ( Park et al, 2021 ). Furthermore, SHARPIN mutants ( Park et al, 2021 ) of the LUBAC complex are highly significantly correlated with a reduction in the thickness of the entorhinal cortex, one of the earliest signs of AD ( Kobro-Flatmoen et al, 2021 ; Figures 3A,B ).…”

“…In this line, human SHARPIN mutants were shown to have less capability of NF-κB activation ( Park et al, 2021 ). Furthermore, SHARPIN mutants ( Park et al, 2021 ) of the LUBAC complex are highly significantly correlated with a reduction in the thickness of the entorhinal cortex, one of the earliest signs of AD ( Kobro-Flatmoen et al, 2021 ; Figures 3A,B ). Soheili-Nezhad et al (2020) identified a SHARPIN mutant in AD associated with degeneration of the limbic system and its interconnecting white-matter.…”