Abstract
Insulin has been commonly adopted as a peptide drug to treat diabetes as it facilitates the uptake of glucose from the blood. The development of oral insulin remains elusive over decades owing to its susceptibility to the enzymes in the gastrointestinal tract and poor permeability through the intestinal epithelium upon dimerization. Recent experimental studies have revealed that certain O-linked glycosylation patterns could enhance insulin’s proteolytic stability and reduce its dimerization propensity, but understanding such phenomena at the molecular level is still difficult. To address this challenge, we proposed and tested several structural determinants that could potentially influence insulin’s proteolytic stability and dimerization propensity. We used these metrics to assess the properties of interest from \(10\ \mu \hbox {s}\) aggregate molecular dynamics of each of 12 targeted insulin glyco-variants from multiple wild-type crystal structures. We found that glycan-involved hydrogen bonds and glycan-dimer occlusion were useful metrics predicting the proteolytic stability and dimerization propensity of insulin, respectively, as was in part the solvent-accessible surface area of proteolytic sites. However, other plausible metrics were not generally predictive. This work helps better explain how O-linked glycosylation influences the proteolytic stability and monomeric propensity of insulin, illuminating a path towards rational molecular design of insulin glycoforms.
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Data availability
As discussed in Section Analysis techniques, most values reported in our results are averaged over different wild-type crystal structure models. For individual analysis result of each insulin glycoform, please refer to our GitHub repository of the project. The repository also contains input configurations/MD parameters and Python codes for data analysis. The outputs of the MD trajectories are too large to release as they are several terabytes in size and statistically representative outputs can be generated from the input files.
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Acknowledgements
Research reported in this publication was primarily supported by the National Institute of Biomedical Imaging and Bioengineering of the National Institutes of Health under award number R01EB025892. This work was also supported in part by the NIH/CU Molecular Biophysics Graduate Traineeship T32 GM065103 and the CAMS Innovation Fund for Medical Sciences (CIFMS 2021-1-I2M-026). The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
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Contributions based on CRediT taxonomy: W.-T.H.: Conceptualization, Writing – Original Draft, Writing – Review & Editing, Methodology, Investigation D.A.R.: Writing – Original Draft, Writing -Review & Editing, Methodology, Investigation T.S.: Conceptualization, Writing – Review & Editing, Funding Acquisition Z.T.: Conceptualization, Writing – Review & Editing, Funding Acquisition M.R.S.: Conceptualization, Writing – Review & Editing, Supervision, Funding Acquisition
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M.R.S. is an Open Science Fellow at and consults for Roivant Sciences.
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Hsu, WT., Ramirez, D.A., Sammakia, T. et al. Identifying signatures of proteolytic stability and monomeric propensity in O-glycosylated insulin using molecular simulation. J Comput Aided Mol Des 36, 313–328 (2022). https://doi.org/10.1007/s10822-022-00453-6
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DOI: https://doi.org/10.1007/s10822-022-00453-6