Structural basis of glycogen branching enzyme deficiency and pharmacologic rescue by rational peptide design

D. Sean Froese, Amit Michaeli, Thomas J. McCorvie, Tobias Krojer, Meitav Sasi, Esther Melaev, Amiram Goldblum, Maria Zatsepin, Alexander Lossos, Rafael Álvarez, Pablo V. Escribá, Berge A. Minassian, Frank Von Delft, Or Kakhlon, Wyatt W. Yue

Research output: Contribution to journalArticle

21 Scopus citations

Abstract

Glycogen branching enzyme 1 (GBE1) plays an essential role inglycogenbiosynthesis by generating a-1,6-glucosidic branches from α-1,4-linked glucose chains, to increase solubility of the glycogen polymer. Mutations in the GBE1 gene lead to the heterogeneous early-onset glycogen storage disorder type IV (GSDIV) or the late-onset adult polyglucosan body disease (APBD). To better understand this essential enzyme, we crystallized human GBE1 in the apo form, and in complex with a tetra- or hepta-saccharide. The GBE1 structure reveals a conservedamylase core that houses the active centre for the branching reaction and harbours almost all GSDIV andAPBDmutations. Anon-catalytic binding cleft, proximal to the site of the common APBDmutation p.Y329S,was found to bind the tetra- and hepta-saccharides andmay represent a higher-affinity site employed to anchor the complex glycogen substrate for the branching reaction. Expression of recombinant GBE1-p.Y329S resulted in drastically reduced protein yield and solubility compared with wild type, suggesting this disease allele causes protein misfolding and may be amenable to small molecule stabilization. To explore this, we generated a structural model of GBE1-p.Y329S and designed peptides ab initio to stabilize the mutation. As proof-of-principle, we evaluated treatment of one tetra-peptide, Leu-Thr-Lys-Glu, in APBD patient cells. We demonstrate intracellular transport of this peptide, its binding and stabilization of GBE1-p.Y329S, and 2-fold increased mutant enzymatic activity compared with untreated patient cells. Together, our data provide the rationale and starting point for the screening of small molecule chaperones, which could become novel therapies for this disease.

Original languageEnglish (US)
Pages (from-to)5667-5676
Number of pages10
JournalHuman Molecular Genetics
Volume24
Issue number20
DOIs
StatePublished - Jun 5 2015

ASJC Scopus subject areas

  • Molecular Biology
  • Genetics
  • Genetics(clinical)

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    Sean Froese, D., Michaeli, A., McCorvie, T. J., Krojer, T., Sasi, M., Melaev, E., Goldblum, A., Zatsepin, M., Lossos, A., Álvarez, R., Escribá, P. V., Minassian, B. A., Von Delft, F., Kakhlon, O., & Yue, W. W. (2015). Structural basis of glycogen branching enzyme deficiency and pharmacologic rescue by rational peptide design. Human Molecular Genetics, 24(20), 5667-5676. https://doi.org/10.1093/hmg/ddv280