Competitive Inhibition of the Endoplasmic Reticulum Signal Peptidase by Non-cleavable Mutant Preprotein Cargos
Upon translocation across the endoplasmic reticulum (ER) membrane, secretory proteins are proteolytically processed to remove their signal peptide by signal peptidase (SPase). This process is critical for subsequent folding, intracellular trafficking, and maturation of secretory proteins. Prokaryoti...
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Veröffentlicht in: | The Journal of biological chemistry 2015-11, Vol.290 (47), p.28131-28140 |
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Sprache: | eng |
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Zusammenfassung: | Upon translocation across the endoplasmic reticulum (ER) membrane, secretory proteins are proteolytically processed to remove their signal peptide by signal peptidase (SPase). This process is critical for subsequent folding, intracellular trafficking, and maturation of secretory proteins. Prokaryotic SPase has been shown to be a promising antibiotic target. In contrast, to date, no eukaryotic SPase inhibitors have been reported. Here we report that introducing a proline immediately following the natural signal peptide cleavage site not only blocks preprotein cleavage but also, in trans, impairs the processing and maturation of co-expressed preproteins in the ER. Specifically, we find that a variant preproinsulin, pPI-F25P, is translocated across the ER membrane, where it binds to the catalytic SPase subunit SEC11A, inhibiting SPase activity in a dose-dependent manner. Similar findings were obtained with an analogous variant of preproparathyroid hormone, demonstrating that inhibition of the SPase does not depend strictly on the sequence or structure of the downstream mature protein. We further show that inhibiting SPase in the ER impairs intracellular processing of viral polypeptides and their subsequent maturation. These observations suggest that eukaryotic SPases (including the human ortholog) are, in principle, suitable therapeutic targets for antiviral drug design.
Background: Signal peptidase (SPase) excises the signal peptide of secretory preproteins.
Results: A variant preproinsulin with a proline following the signal peptide cleavage site binds to and inhibits SPase.
Conclusion: Inhibition of SPase impairs, in trans, the intracellular processing, trafficking, and maturation of secretory proteins and viral polypeptides.
Significance: Our findings suggest eukaryotic SPase as a potential antiviral target. |
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ISSN: | 0021-9258 1083-351X |
DOI: | 10.1074/jbc.M115.692350 |