P40 and P75 Are Singular Functional Muramidases Present in the Lactobacillus casei /paracasei/rhamnosus Taxon

Abstract

Lactobacillus casei and Lactobacillus rhamnosus proteins P40 and P75 belong to a large family of secreted cell wall proteins that contain a carboxy(C)-terminal CHAP or NlpC/P60 superfamily domains. In addition to their peptidoglycan hydrolases activity, proteins in this family are specific antigens of pathogens, frequently responsible of interactions with the host. L. rhamnosus GG and L. casei BL23 purified P40 and P75 proteins have antiapoptotic activity by inducing the EGF/Akt pathway. The aim of this work was to study the genetics, phylogeny and dissemination of this family of proteins in the genus Lactobacillus as well as their characteristics and likely function. The scrutiny of their DNA encoding sequences revealed the presence of minisatellite DNA in the P75 encoding gene of L. casei/paracasei strains ( cmu B) with intraspecific indels that gave raise to four different alleles ( cmu B1–4), which are exclusive of this species. Phylogenic analyses suggest that both proteins are present mainly in the L. casei and Lactobacillus sakei phylogenomic groups. A P40 ancestral gene was possibly present in the common ancestor of Enterococcaceae , Lactobacillaceae and Streptococcaceae . P75 is also present in L. casei and L. sakei groups, but its evolution is difficult to explain only by vertical transmission. Antibodies raised against the N-terminal regions of P40 and P75 improved their immunological detection in culture supernatants as they recognized almost exclusively proteins of L. casei/paracasei/rhamnosus strains, highlighting their structural similarity, that allowed to detect them in different fermented dairy products that contained probiotic L. casei strains. Purified P40 and P75 proteins showed no evident lytic activity but they complemented L. casei BL23 cmu A and cmu B defective mutants, respectively, thus proving that they actively participate in cell division.

Paraprobiotics and Postbiotics of Probiotic Lactobacilli, Their Positive Effects on the Host and Action Mechanisms: A Review

“…Protein p40 and p75 were identified from many Lactobacilli species including L. casei, L. paracasei, and L. rhamnosus (145). They are secreted cell wall muramidases and have approximately molecular sizes of 40 and 75 kDa, respectively (74).…”

“…The p40 transactivated the epidermal growth factor receptor (EGFR) in intestinal epithelial cells, inhibited apoptosis and preserved barrier function in the colon, thereby ameliorating intestinal injury and inflammation (17, 75, 76, 78, 109). Besides, p75 purified from L. rhamnosus GG and L. casei BL23 have anti-apoptotic activity by inducing the EGF/Akt pathway (145). Furthermore, the p40 and p75 proteins were able to protect the intestinal epithelial tight junctions and barrier functions by a protein kinase (PKC) and MAP kinase-dependent mechanism (76).…”

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

“…Lactobacillus casei BL23 (BL23) is a well-studied probiotic strain for which anti-inflammatory and anti-tumor effect have been described in mouse models 22 – 25 . Two secreted cell wall muramidases that contain a CHAP (NlpC/P60) domain have been characterized in BL23, P40 and P75, and homologs to these proteins are exclusively present in the L. casei taxon, that comprises mainly the species L. casei, L. paracasei and L. rhamnosus 26 . Their ability to stimulate growth and survival of epithelial cells was first described in L. rhamnosus GG 27 .…”

“…These proteins proved to have anti-apoptotic and anti-inflammatory effects mediated by the activation of the EGFR/Akt pathway. Then, it was shown that protein P40 reduces dextran sulfate sodium (DSS)-induced experimental colitis, and it induced mucin synthesis by intestinal epithelial cells (IEC), intestinal IgA production and promoted intestinal development in early life 26 , 28 – 31 . The abnormal cellular morphology of knock out mutants of L. casei and L. rhamnosus lacking these proteins showed that they are involved in the normal conformation of the bacterial cell wall; P75 is a γ-D-glutamyl-L-lysyl-endopeptidase required for daughter cell separation 28 , 32 .…”

The Neglected Microbial Components of Commercial Probiotic Formulations

“…Therefore, the lyophilized microbial biomass used to prepare a probiotic product contains the residual growth medium, which includes microbial metabolites produced and secreted/released by probiotic cells during growth. Such microbial products may include primary metabolites (e.g., lactate, acetate, propionate), bacteriocins, reuterin, or other secreted molecules (e.g., immunomodulatory secreted peptides; [43]), which can be defined as "postbiotics" [44]. The actual contribution of these molecules to the interaction of probiotic formulations on host health is not known but, in light of data obtained from in vitro experiments, cannot be excluded [45][46][47].…”