Pietro Roversi

Based at the IRC Institute of Agricultural Biology and Biotechnology (Italy)

ERQC/ERAD modulation for broad-spectrum glycoprotein secretion-rescue in rare disease

Research summary

Wonderfully efficient protein folding surveillance machineries in the Endoplasmic Reticulum (ER) of eukaryotic cells ensure that only correctly folded glycoproteins can exit the ER and proceed to the Golgi, and from the Golgi continue along the secretory pathway towards their individual cellular or extracellular destinations: ER Quality Control (ERQC) helps glycoproteins to fold and retains them in the ER until they are ready to leave; ER Associated Degradation (ERAD) dispatches any hopelessly misfolded glycoproteins to a cytoplasmic shredder (see Figure).

The stringency of ERQC and ERAD – while of great advantage to healthy cells – can originate severe disease in patients carrying mutant glycoproteins: the latter are detected as incorrectly folded, retained in the ER and eventually degraded. ERQC/ERAD zeal bears particularly unfortunate consequences when the mutation affecting the glycoprotein is mild, i.e. it impairs but does not abrogate its function (“responsive mutant”). In these cases, secretion of the mutated competent glycoprotein never takes place - and disease ensues.

We postulate that in rare disease patients carrying responsive glycoprotein mutants, small molecule modulators of ERQC/ERAD would rescue the secretion and residual activity of slightly misfolded and yet still active glycoproteins, thus alleviating pathogenic symptoms. The fraction of responsive patients who could derive therapeutic benefit from ERQC/ERAD modulation therapy depends on the disease, and varies between 70% in cystic fibrosis patients to 15-50% in lysosomal storage diseases.

In order to develop and test ERQC/ERAD partial inhibitors as broad-spectrum rescuers of secretion for responsive mutant glycoproteins, we investigate the molecular mechanisms by which the eukaryotic cell eitherERQC retains misfolded glycoproteins in the ER and/or how ERAD degrades them by ERAD. Cryo-EM and X-ray crystallography of recombinantly expressed purified ERQC/ERAD proteins and their complexes with misfolded substrates are used to generate a range of biochemical and biological hypotheses, then tested by in vitro and in cellular assays, and in vivo experiments using the plant as a model organism.

Pietro’s experiments are discussed in the Open Secretion Rescue blog at SGC Toronto

Key publications

• Destro R, Roversi P, Barzaghi M, Lo Presti L. (2021) Anharmonic Thermal Motion Modelling in the Experimental XRD Charge Density Determination of 1-Methyluracil at T = 23 K. Molecules 26, 3075. https://doi.org/ 10.3390/molecules26113075
• Modenutti CP, Blanco Capurro JI, Ibba R, Alonzi DS, Song MN, Vasiljević S, Kumar A, Chandran AV, Tax G, Marti L, Hill JC,  Lia A,  Hensen M, Waksman T,  Rushton J,  Rubichi S,  Santino A, Martí MA,  Zitzmann N,  Roversi P(2020), Clamping, bending, and twisting inter-domain motions in the misfold-recognizing portion of UDP-glucose:glycoprotein glucosyltransferase, Structure 29, 4, 357-370
• Lia A, Dowle A, Taylor C, Santino A, Roversi P. (2020) Partial catalytic Cys oxidation of human GAPDH to Cys-sulfonic acid. Wellcome Open Res. 2020 Aug 25;5:114. doi: 10.12688/wellcomeopenres.15893.2. eCollection 2020. PMID: 32802964
• Warfield KL, Alonzi DS, Hill JC, Caputo AT, Roversi P, Kiappes JL, Sheets N, Duchars M, Dwek RA, Biggins J, Barnard D, Shresta S, Treston AM, Zitzmann N. J (2020) Targeting Endoplasmic Reticulum α-Glucosidase I with a Single-Dose Iminosugar Treatment Protects against Lethal Influenza and Dengue Virus Infections. Med Chem. 63(8):4205-4214. doi: 10.1021/acs.jmedchem.0c00067. Epub 2020 Apr 15. PMID: 32227946
• Tax G, Lia A, Santino A, Roversi P Modulation of ERQC and ERAD: A Broad-Spectrum Spanner in the Works of Cancer Cells?J Oncol. 2019 Oct 1;2019:8384913. doi: 10.1155/2019/8384913. eCollection 2019
• Lia A, Gallo A, Marti L, Roversi P, Santino A.EFR-Mediated Innate Immune Response in Arabidopsis thaliana is a Useful Tool for Identification of Novel ERQC Modulators Genes 10 (1), 15
• Roversi P, et al. (2017) 'Interdomain conformational flexibility underpins the activity of UGGT, the eukaryotic glycoprotein secretion checkpoint.' Proc Natl Acad Sci USA, vol. 114. Pp. 8544–8549.
• Caputo AT, et al. (2016) 'Structures of mammalian ER α-glucosidase II capture the binding modes of broad-spectrum iminosugar antivirals.' Proc Natl Acad Sci USA, vol. 113. Pp. E4630–8
• Yong SC & Roversi P, et al. (2014) 'A complex iron-calcium cofactor catalyzing phosphotransfer chemistry.' Science, vol. 345. Pp.1170– 1173

Former group members

Andrea Lia, Gábor Tax