ANXA11 mutations in ALS cause dysregulation of calcium homeostasis and stress granule dynamics

Minyeop Nahm1,2, Su Min Lim1,2, Young-Eun Kim3, Jinseok Park1, Min-Young Noh1,2, Sanggon Lee1, Ju Eun Roh4, Sung-Min Hwang4, Chul-Kyu Park4, Yong Ho Kim4, GyuTae Lim5,6, Jinhyuk Lee5,6, Ki-Wook Oh1, Chang-Seok Ki7, Seung Hyun Kim8,2

  1. Department of Neurology, College of Medicine, Hanyang University, Seoul 04763, Korea.
  2. Biomedical Research Institute, Hanyang University, Seoul 04763, Korea.
  3. Department of Laboratory Medicine, College of Medicine, Hanyang University, Seoul 04763, Korea.
  4. Gachon Pain Center and Department of Physiology, College of Medicine, Gachon University, Incheon 21999, Korea.
  5. Genome Editing Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), Daejeon 34141, Korea.
  6. Department of Bioinformatics, KRIBB School of Bioscience, University of Science and Technology (UST), Daejeon 34113, Korea.
  7. Green Cross Genome Corporation, Yongin 16924, Korea.
  8. Department of Neurology, College of Medicine, Hanyang University, Seoul 04763, Korea. kimsh1@hanyang.ac.kr.

Abstract

Dysregulation of calcium ion homeostasis and abnormal protein aggregation have been proposed as major pathogenic hallmarks underpinning selective degeneration of motor neurons in amyotrophic lateral sclerosis (ALS). Recently, mutations in annexin A11 (ANXA11), a gene encoding a Ca2+-dependent phospholipid-binding protein, have been identified in familial and sporadic ALS. However, the physiological and pathophysiological roles of ANXA11 remain unknown. Here, we report functions of ANXA11 related to intracellular Ca2+ homeostasis and stress granule dynamics. We analyzed the exome sequences of 500 Korean patients with sALS and identified nine ANXA11 variants in 13 patients. The amino-terminal variants p.G38R and p.D40G within the low-complexity domain of ANXA11 enhanced aggregation propensity, whereas the carboxyl-terminal ANX domain variants p.H390P and p.R456H altered Ca2+ responses. Furthermore, all four variants in ANXA11 underwent abnormal phase separation to form droplets with aggregates and led to the alteration of the biophysical properties of ANXA11. These functional defects caused by ALS-linked variants induced alterations in both intracellular Ca2+ homeostasis and stress granule disassembly. We also revealed that p.G228Lfs*29 reduced ANXA11 expression and impaired Ca2+ homeostasis, as caused by missense variants. Ca2+-dependent interaction and coaggregation between ANXA11 and ALS-causative RNA-binding proteins, FUS and hnRNPA1, were observed in motor neuron cells and brain from a patient with ALS-FUS. The expression of ALS-linked ANXA11 variants in motor neuron cells caused cytoplasmic sequestration of endogenous FUS and triggered neuronal apoptosis. Together, our findings suggest that disease-associated ANXA11 mutations can contribute to ALS pathogenesis through toxic gain-of-function mechanisms involving abnormal protein aggregation.

Presented By Su-Min Lim | ORCID iD

NeuroscienceNicholas Liao2020-10 (Oct)