Dissecting Mutational Allosteric Effects in Alkaline Phosphatases Associated with Different Hypophosphatasia Phenotypes: An Integrative Computational Investigation

Abstract

Hypophosphatasia (HPP) is a rare inherited disorder characterized by defective bone mineralization, is highly variable in its clinical phenotype. The disease occurs due to various loss-of-function mutations in ALPL, the gene encoding tissue-nonspecific alkaline phosphatase (TNSALP). In this work, a data-driven and biophysics-based approach for large-scale analysis of ALPL mutations - from nonpathogenic to severe HPPs is proposed. Allosteric molecular signatures of ALPL mutations were determined using an integrated pipeline of synergistic approaches including sequence and energetic-based analysis, structural topology network modeling and elastic network models. Statistical analysis of molecular features computed for the ALPL mutations showed a significant difference between the control and mild and severe HPP phenotypes, and the developed machine learning model suggested that the topological network parameters could serve as is a robust indicator for severe mutations. Molecular dynamics simulations coupled with protein structure network was employed to analyze the effect of single-residue variation on conformational dynamics of TNSALP dimers, and we found that severe disease-associated mutations have a significantly greater effect on allosteric communications. The results of this study suggested that ALPL mutations associated with mild and severe HPPs tend to have different effects on protein stability on local scale and long-range communications caused by network rewiring. By linking disease phenotypes with allosteric molecular signatures, the proposed integrative computational approach elucidates the complex sequence-structure-allostery relationships of ALPL mutations and dissects the role of allosteric effects in the pathogenesis of HPPs. Author SummaryThe understanding of mutational genotype- disease phenotype relationship is a fundamental step for enabling precision medicine. It remains a challenging task to assess the molecular principle of the genotype- phenotype relationship. By focusing on Hypophosphatasia, a rare inherited disorder, as an example, we performed comprehensive analysis of single-amino-acid mutations in the encoded protein of Tissue Nonspecific Alkaline Phosphatase associated in terms of their sequence, structure, and dynamics properties. We further developed a machine learning -based method to classify different disease phenotypes, and the interpretability of the classification model was addressed by the structural-functional analysis of network topological important mutations. Our results highlighted the allosteric propensity of severe mutations, and show the potential allosteric principle of genotype- phenotype relationship.