The N‐ and C‐terminal fragments of ubiquitin are important for the antimicrobial activities

Abstract

Secretory granules of chromaffin cells contain catecholamines and several antimicrobial peptides derived from chromogranins and proenkephalin-A. These peptides are secreted in the extracellular medium following exocytosis. Here, we show that ubiquitin is stored in secretory chromaffin granules and released into the circulation upon stimulation of chromaffin cells. We also show that the C-terminal fragment (residues 65-76) of ubiquitin displays, at the micromolar range, a lytic antifungal activity. Using confocal laser scan microscopy and rhodamine-labeled synthetic peptides, we could demonstrate that the C-terminal peptide (residues 65-76) is able to cross the cell wall and the plasma membrane of fungi and to accumulate in fungi, whereas the N-terminal peptide (residues 1-34) is stopped at the fungal wall level. Furthermore, these two peptides act synergistically to kill filamentous fungi. Because of the interaction of the C-terminal sequence of ubiquitin with calmodulin, the synthetic peptide (residues 65-76) was tested in vitro against calmodulin-dependent calcineurin, an enzyme crucial for fungal growth. This peptide was found to inhibit the phosphatase activity of calcineurin. Our data show a new property of ubiquitin C-terminal-derived peptide (65-76) that could be used with N-terminal peptide (1-34) as a new potent antifungal agent.

Lysosomal killing ofMycobacteriummediated by ubiquitin-derived peptides is enhanced by autophagy

“…2B) that exhibited differential activity against fungal and bacterial pathogens. We synthesized peptides corresponding to these sequences and found, consistent with the published data (28), that no activity was observed with Ub1, but Ub2 was capable of mediating significant antibacterial activity against both M. smegmatis and M. tuberculosis. Using a growth inhibition assay on M. tuberculosis, we determined that the Ub2 peptide exhibited an minimum inhibitory concentration of 5 M, indicating potent antimyco- bacterial activity that is consistent with the concentrations of ubiquitin found in the SFs (Fig.…”

“…Previous work by Kieffer et al reported that peptides derived from ubiquitin were capable of microbicidal activity against a range of organisms (28). They identified two endoproteinasederived peptide sequences Ub1 and Ub2 (Fig.…”

“…Ubiquitin has been identified as a constituent of several extracts that have antibacterial activity, including medium conditioned by insect cells, the mucosal layers of the colon and cervix, and the secretory granules of chromaffin cells (27)(28)(29)(30). To demonstrate formally that ubiquitin was capable of killing Mycobacterium, we incubated purified ubiquitin with bacteria in vitro and found that intact ubiquitin did not display bactericidal activity.…”

Systemic Ubiquitin Release After Blunt Trauma and Burns: Association With Injury Severity, Posttraumatic Complications, and Survival

“…17 However, patients who were admitted to the emergency room after an accident but did not suffer from any injuries (ISS 0) did not show a significant increase in Ub serum concentrations, as compared with healthy volunteers. Thus, the contribution of Ub that is actively secreted during the stress response to its overall concentration in the systemic circulation after blunt trauma and burns is probably small.…”

“…13,14 Because other investigators provided evidence that it also regulates growth and apoptosis, and possesses antimicro-bial activity, [15][16][17] extracellular Ub may have pleiotropic effects on host defense mechanisms. Subsequently, we were able to confirm Ubs immune modulatory properties in vivo and showed that it has profound anti-inflammatory effects in various models of infectious and noninfectious inflammation.…”