Computational and functional characterization of Angiogenin mutations, and correlation with amyotrophic lateral sclerosis.

Aditya K Padhi,James Gomes,Manidipa Banerjee,Kamalika Banerjee,David R Borchelt

doi:10.1371/journal.pone.0111963

Aditya K Padhi, James Gomes + Show 3 more

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https://doi.org/10.1371/journal.pone.0111963

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Journal: PloS one	Publication Date: Nov 5, 2014
Citations: 14	License type: CC BY 4.0

Affiliation: Indian Institute of Technology Delhi

Abstract

The Angiogenin (ANG) gene is frequently mutated in patients suffering from the neurodegenerative disease - amyotrophic lateral sclerosis (ALS). Most of the ALS-causing mutations in Angiogenin affect either its ribonucleolytic or nuclear translocation activity. Here we report the functional characterization of two previously uncharacterized missense mutations in Angiogenin - D22G and L35P. We predict the nature of loss-of-function(s) in these mutants through our previously established Molecular Dynamics (MD) simulation extended to 100 ns, and show that the predictions are entirely validated through biochemical studies with wild-type and mutated proteins. Based on our studies, we provide a biological explanation for the loss-of-function of D22G-Angiogenin leading to ALS, and suggest that the L35P-Angiogenin mutation would probably cause ALS symptoms in individuals harboring this mutation. Our study thus highlights the strength of MD simulation-based predictions, and suggests that this method can be used for correlating mutations in Angiogenin or other effector proteins with ALS symptoms.

Highlights

Amyotrophic Lateral Sclerosis (ALS), known as Lou Gehrig’s disease, is a fatal progressive neurodegenerative disorder characterized by the preferential loss of motor neurons in the brain stem, motor cortex and spinal cord
We showed that while the loss of ribonucleolytic activity of Angiogenin is possibly due to a characteristic conformational switching of the catalytic residue His114, the loss of nuclear translocation activity is due to the local folding of nuclear localization signal residues 31RRR33, resulting in reduction of solvent accessible surface area (SASA)
We extended our previous Molecular Dynamics (MD) simulations to 100 ns, and found that both mutants retained the His114 conformational switching during the longer simulations as well (Figures 2A–2C), while wild-type Angiogenin did not demonstrate any alteration within the catalytic triad

Summary

Introduction

Amyotrophic Lateral Sclerosis (ALS), known as Lou Gehrig’s disease, is a fatal progressive neurodegenerative disorder characterized by the preferential loss of motor neurons in the brain stem, motor cortex and spinal cord. Mutations in a number of genes have been identified as causative factors for ALS. Missense mutations in genes such as SOD1, FUS/TLS, TARDBP, ANG, VAPB, DAO, OPTN, VCP, and a recently identified hexanucleotide-repeat expansion (GGGGCC) in C9ORF72 have been documented to be ALS causative [2,3,4,5]. One of the frequently mutated genes in ALS patients is ANG, which encodes a 14.1 kDa neuroprotective effector, Angiogenin [6]. A total of 29 mutations in ANG have been identified in ALS patients so far, of which 19 missense mutations have been correlated with alterations in the functionality of Angiogenin, and consequent ALS symptoms [11,12]

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