The human allicin-proteome: S-thioallylation of proteins by the garlic defence substance allicin and its biological effects

Abstract

A single clove of edible garlic (Allium sativum L.) of about 10 g produces up to 5 mg of allicin (diallylthiosulfinate), a thiol-reactive sulfur-containing defence substance that gives injured garlic tissue its characteristic smell. Allicin induces apoptosis or necrosis in a dose-dependent manner but biocompatible doses influence cellular metabolism and signalling cascades. Oxidation of protein thiols and depletion of the glutathione pool are thought to be responsible for allicin's physiological effects. Here, we studied the effect of allicin on post-translational thiol-modification in human Jurkat T-cells using shotgun LC-MS/MS analyses. We identified 332 proteins that were modified by S-thioallylation in the Jurkat cell proteome which causes a mass shift of 72 Da on cysteines. Many S-thioallylated proteins are highly abundant proteins, including cytoskeletal proteins tubulin, actin, cofilin, filamin and plastin-2, the heat shock chaperones HSP90 and HSPA4, the glycolytic enzymes GAPDH, ALDOA, PKM as well the protein translation factor EEF2. Allicin disrupted the actin cytoskeleton in murine L929 fibroblasts. Allicin stimulated the immune response by causing Zn2+ release from proteins and increasing the Zn2+-dependent IL-1-triggered production of IL-2 in murine EL-4 T-cells. Furthermore, allicin caused inhibition of enolase activity, an enzyme considered a cancer therapy target. In conclusion, our study revealed the widespread extent of S-thioallylation in the human Jurkat cell proteome and showed effects of allicin exposure on essential cellular functions of selected targets, many of which are targets for cancer therapy.

Interspecies Comparison of the Bacterial Response to Allicin Reveals Species‐Specific Defense Strategies

“…Allicin was shown previously to enhance the activity of cell membrane‐disrupting polymyxins in E. coli , which is in agreement with allicin also affecting the cell envelope of Gram‐negative species. When allicin reaches the periplasm, it may also cause damage to the Gram‐negative cell envelope by impairing cell envelope‐associated processes that are required for structural integrity.…”

“…MinD is usually localized at the cell poles and at mid cell, but delocalizes when the membrane potential is altered by membrane‐depolarizing agents such as gramicidin S or valinomycin, or by pore‐forming compounds such as nisin . Despite previous observations that allicin caused pores in tonoplasts and artificial membranes, allicin, at the concentration tested here, neither caused pore formation nor membrane depolarization in B. subtilis . In congruence with allicin‐response‐associated‐proteins indicating an impairment of the cell envelope, the “bubble assay” indicated reduced cell wall integrity.…”

“…We used these assays to probe for effects of allicin on envelope integrity and function ( Figure ). We first tested if allicin causes pore formation in the cytoplasmic membrane as described for tonoplasts and artificial bilayers using nisin as a positive control. Nisin integrates into the membrane and forms large pores that lead to dissipation of the membrane potential and nutrient and ion leakage …”

“…Allicin was further reported to disturb quorum sensing systems and to eradicate bacterial biofilms . Furthermore, allicin‐induced permeabilization of plant cell membranes, tonoplasts, and artificial lipid‐bilayers, caused by transient pore formation, was reported . This global impact of allicin on physiology results in a broad spectrum of antimicrobial activity against fungi, bacteria, and protozoa, but also affects human cell physiology in a dose‐dependent manner .…”

“…[9,10] Furthermore, allicin-induced permeabilization of plant cell membranes, tonoplasts, and artificial lipid-bilayers, caused by transient pore formation, was reported. [11] This global impact of allicin on physiology results in a broad spectrum of antimicrobial activity against fungi, bacteria, and protozoa, but also affects human cell physiology in a dosedependent manner. [12] In times of multidrug-resistant pathogens spreading worldwide, the unexploited multifaceted mode of action renders allicin and allicin-derivatives promising candidates for combating currently untreatable pathogens.…”