All Publications


  • Homotypic fibrillization of TMEM106B across diverse neurodegenerative diseases. Cell Chang, A., Xiang, X., Wang, J., Lee, C., Arakhamia, T., Simjanoska, M., Wang, C., Carlomagno, Y., Zhang, G., Dhingra, S., Thierry, M., Perneel, J., Heeman, B., Forgrave, L. M., DeTure, M., DeMarco, M. L., Cook, C. N., Rademakers, R., Dickson, D. W., Petrucelli, L., Stowell, M. H., Mackenzie, I. R., Fitzpatrick, A. W. 2022

    Abstract

    Misfolding and aggregation of disease-specific proteins, resulting in the formation of filamentous cellular inclusions, is a hallmark of neurodegenerative disease with characteristic filament structures, or conformers, defining each proteinopathy. Here we show that a previously unsolved amyloid fibril composed of a 135 amino acid C-terminal fragment of TMEM106B is a common finding in distinct human neurodegenerative diseases, including cases characterized by abnormal aggregation of TDP-43, tau, or alpha-synuclein protein. A combination of cryoelectron microscopy and mass spectrometry was used to solve the structures of TMEM106B fibrils at a resolution of 2.7A from postmortem human brain tissue afflicted with frontotemporal lobar degeneration with TDP-43 pathology (FTLD-TDP, n= 8), progressive supranuclear palsy (PSP, n= 2), or dementia with Lewy bodies (DLB, n= 1). The commonality of abundant amyloid fibrils composed of TMEM106B, a lysosomal/endosomal protein, to a broad range of debilitating human disorders indicates a shared fibrillization pathway that may initiate or accelerate neurodegeneration.

    View details for DOI 10.1016/j.cell.2022.02.026

    View details for PubMedID 35247328

  • Crystal structure and functional analysis of mycobacterial erythromycin resistance methyltransferase Erm38 reveals its RNA-binding site JOURNAL OF BIOLOGICAL CHEMISTRY Goh, B., Xiang, X., Lescar, J., Dedon, P. C. 2022; 298 (2): 101571

    Abstract

    Erythromycin resistance methyltransferases (Erms) confer resistance to macrolide, lincosamide, and streptogramin antibiotics in Gram-positive bacteria and mycobacteria. Although structural information for ErmAM, ErmC, and ErmE exists from Gram-positive bacteria, little is known about the Erms in mycobacteria, as there are limited biochemical data and no structures available. Here, we present crystal structures of Erm38 from Mycobacterium smegmatis in apoprotein and cofactor-bound forms. Based on structural analysis and mutagenesis, we identified several catalytically critical, positively charged residues at a putative RNA-binding site. We found that mutation of any of these sites is sufficient to abolish methylation activity, whereas the corresponding RNA-binding affinity of Erm38 remains unchanged. The methylation reaction thus appears to require a precise ensemble of amino acids to accurately position the RNA substrate, such that the target nucleotide can be methylated. In addition, we computationally constructed a model of Erm38 in complex with a 32-mer RNA substrate. This model shows the RNA substrate stably bound to Erm38 by a patch of positively charged residues. Furthermore, a π-π stacking interaction between a key aromatic residue of Erm38 and a target adenine of the RNA substrate forms a critical interaction needed for methylation. Taken together, these data provide valuable insights into Erm-RNA interactions, which will aid subsequent structure-based drug design efforts.

    View details for DOI 10.1016/j.jbc.2022.101571

    View details for Web of Science ID 000761371500015

    View details for PubMedID 35007529

    View details for PubMedCentralID PMC8844858

  • Long-range structural defects by pathogenic mutations in most severe glucose-6-phosphate dehydrogenase deficiency. Proceedings of the National Academy of Sciences of the United States of America Horikoshi, N. n., Hwang, S. n., Gati, C. n., Matsui, T. n., Castillo-Orellana, C. n., Raub, A. G., Garcia, A. A., Jabbarpour, F. n., Batyuk, A. n., Broweleit, J. n., Xiang, X. n., Chiang, A. n., Broweleit, R. n., Vöhringer-Martinez, E. n., Mochly-Rosen, D. n., Wakatsuki, S. n. 2021; 118 (4)

    Abstract

    Glucose-6-phosphate dehydrogenase (G6PD) deficiency is the most common blood disorder, presenting multiple symptoms, including hemolytic anemia. It affects 400 million people worldwide, with more than 160 single mutations reported in G6PD. The most severe mutations (about 70) are classified as class I, leading to more than 90% loss of activity of the wild-type G6PD. The crystal structure of G6PD reveals these mutations are located away from the active site, concentrating around the noncatalytic NADP+-binding site and the dimer interface. However, the molecular mechanisms of class I mutant dysfunction have remained elusive, hindering the development of efficient therapies. To resolve this, we performed integral structural characterization of five G6PD mutants, including four class I mutants, associated with the noncatalytic NADP+ and dimerization, using crystallography, small-angle X-ray scattering (SAXS), cryogenic electron microscopy (cryo-EM), and biophysical analyses. Comparisons with the structure and properties of the wild-type enzyme, together with molecular dynamics simulations, bring forward a universal mechanism for this severe G6PD deficiency due to the class I mutations. We highlight the role of the noncatalytic NADP+-binding site that is crucial for stabilization and ordering two β-strands in the dimer interface, which together communicate these distant structural aberrations to the active site through a network of additional interactions. This understanding elucidates potential paths for drug development targeting G6PD deficiency.

    View details for DOI 10.1073/pnas.2022790118

    View details for PubMedID 33468660