Lactobacillus casei extracellular vesicles stimulate EGFR pathway likely due to the presence of proteins P40 and P75 bound to their surface

Abstract

In the complex interplay of beneficial bacteria with the host, there are few examples of bacterial metabolites and effector molecules that have been consistently identified. Protective effects on the intestinal epithelium have been ascribed to P40 and P75, two well characterized cell wall muramidases, present in the culture supernatant of strains belonging to the taxon Lactobacillus casei/paracasei/rhamnosus. This work reports that Lactobacillus casei BL23 extracellular vesicles (BL23 EVs) have a small size (17–20 nm or 24–32 nm, depending on the method used) and contain lipoteichoic acid (LTA). Interestingly, all detected P40 and most of P75 were associated to EVs and possibly located at their external surface, as shown by proteinase K digestion. Biosensor assays showed that both proteins bind LTA and vesicles, suggesting that they could bind to ligands like LTA present on BL23 EVs. Native BL23 EVs have a moderate proinflammatory effect and they were able to induce phosphorylation of the epidermal growth factor receptor (EGFR), showing an effect similar to purified P40 and P75 and leading to the conclusion that the activity described in the supernatant (postbiotic) of these bacteria would be mainly due to P40 and P75 bound to EVs.

Probiotics, Their Extracellular Vesicles and Infectious Diseases

“…At the same time, L. rhamnosus EVs had the same effect in an in vivo model of dextran sulfate sodium-induced colitis in mice ( Tong et al, 2021 ). On the other hand, EVs from E. coli and L. casei increased NF-κB levels per se in Caco-2 and HT-29 cell lines ( Cañas et al, 2018 ; Bäuerl et al, 2020 ). This opposite modulation of NFκB levels, in the presence or absence of LPS, was also observed for pro-inflammatory cytokines like IL-8 in both Caco-2 and HT-29 cell lines, and in ex vivo human colonic explant ( Fábrega et al, 2016 ; Choi et al, 2020 ; Vargoorani et al, 2020 ).…”

“…In vitro and in vivo experiments with intestinal epithelial cells have demonstrated that EVs released by E. coli , L. casei , L. paracasei , P. freudenreichii , and L. rhamnosus can modulate NFκB levels ( Cañas et al, 2018 ; Bäuerl et al, 2020 ; Choi et al, 2020 ; Vargoorani et al, 2020 ; Tong et al, 2021 ). NF-κB is a family of transcription factors and has an essential role in a variety of aspects related with human health including the development of both innate and adaptive immunity.…”

“…For p40, this effect was also observed in a murine model of colitis ( Yan et al, 2011 ). EGFR activation can also be triggered by L. casei EVs, which expose p40 and p75 at the surface ( Bäuerl et al, 2020 ). Intriguingly, EVs from L. rhamnosus GG were shown to have apoptotic effects in hepatic cancer cells by the intrinsic pathway of apoptosis ( Behzadi et al, 2017 ).…”

“…It has been shown that EVs from probiotics contain proteins that could mediate pathogen inhibition, and in this way could possibly compete with pathogens for colonization in the intestine ( Domínguez Rubio et al, 2017 ; Bajic et al, 2020 ; Bäuerl et al, 2020 ; Nishiyama et al, 2020 ). Proteomic analyses of EVs from three different lactobacilli strains showed that protein composition of EVs can be very different among species ( Dean et al, 2019 ).…”

Intestinal Infection of Candida albicans: Preventing the Formation of Biofilm by C. albicans and Protecting the Intestinal Epithelial Barrier

“…Vitro research results demonstrate that M3 receptor-induced activation of p38 MAPK might maintain epithelial barrier function by downregulating TNF-α signaling and activation of Epidermal growth factor receptors (EGFR) instead of H1 (Uwada et al, 2017). Both P40 and P75 proteins were shown to show anti-apoptotic features containing EGFR phosphorylation and, in the case of P40, preventing the intestinal epithelium from triggered inflammation in a vitro model (Bauerl et al, 2020) (Figure 4).…”