Epithelial Adhesion Mediated by Pilin SpaC Is Required for Lactobacillus rhamnosus GG-Induced Cellular Responses

Abstract

Lactobacillus rhamnosus GG is a widely used probiotic, and the strain's salutary effects on the intestine have been extensively documented. We previously reported that strain GG can modulate inflammatory signaling, as well as epithelial migration and proliferation, by activating NADPH oxidase 1-catalyzed generation of reactive oxygen species (ROS). However, how strain GG induces these responses is unknown. Here, we report that strain GG's probiotic benefits are dependent on the bacterial-epithelial interaction mediated by the SpaC pilin subunit. By comparing strain GG to an isogenic mutant that lacks SpaC (strain GG⍀spaC), we establish that SpaC is necessary for strain GG to adhere to gut mucosa, that SpaC contributes to strain GG-induced epithelial generation of ROS, and that SpaC plays a role in strain GG's capacity to stimulate extracellular signal-regulated kinase/mitogen-activated protein kinase (ERK/MAPK) signaling in enterocytes. In addition, we show that SpaC is required for strain GG-mediated stimulation of cell proliferation and protection against radiologically inflicted intestinal injury. The identification of a critical surface protein required for strain GG to mediate its probiotic influence advances our understanding of the molecular basis for the symbiotic relationship between some commensal bacteria of the gut lumen and enterocytes. Further insights into this relationship are critical for the development of novel approaches to treat intestinal diseases.

Sex steroid deficiency–associated bone loss is microbiota dependent and prevented by probiotics

“…bind to the intestinal mucus layer and for LGG to exert its positive influence on gut tissue health (63). The fact that LGGM maintained a degree of protection from bone loss suggests that direct contact with the mucus layer may not be the only mode by which LGG exerts probiotic effects and that other properties of LGG -such as the production of short chain fatty acids, which have been shown to modulate cytokine levels in the intestine -is also a mechanism to consider (79).…”

“…Mice were supplemented by oral gavage with vehicle or purified cultures of the extensively studied probiotic LGG, or with commercially available VSL#3 preparation, which contains 8 strains of live bacteria -Bifidobacterium breve, Bifidobacterium longum, Bifidobacterium infantis, Lactobacillus acidophilus, Lactobacillus plantarum, Lactobacillus paracasei, Lactobacillus bulgaricus, and Streptococcus thermophilus -over a 4-week period. Additional control groups of sham-operated and ovx mice were treated with purified cultures of laboratory E. coli DH5alpha, a strain that does not exert a probiotic effect, and the LGG pili mutant LGG(ΔSpaC), herein referred to as LGGMa strain with defective epithelial adhesion -which is required for LGG-induced cellular responses (63). Mice were fed 1 × 10 9 total bacteria at 3.5-day intervals for 4 weeks.…”

Polymorphisms, Chromosomal Rearrangements, and Mutator Phenotype Development during Experimental Evolution of Lactobacillus rhamnosus GG

“…5B) also had a substitution mutation within the spaC gene that introduced a stop codon (coordinate 446541; CAG ¡ TAG; Q ¡ STOP). SpaC is the tip pilin and has been shown to be associated with mucus binding (20,47,48). Such a mutation is predicted to truncate the SpaC protein and therefore to abolish the mucus-binding properties of L. rhamnosus N1, N3, and N8.…”

Genomic Characterization of Non-Mucus-Adherent Derivatives of Lactobacillus rhamnosus GG Reveals Genes Affecting Pilus Biogenesis

“…Among the Gram-positive bacteria, pili have been previously found on the surface of pathogens such as Corynebacterium diphtheriae (13) and Enterococcus faecalis (14), where they are considered virulence factors and mediate interactions with the host. Hence, it is likely that L. rhamnosus GG pili are also involved in host signaling; their immunomodulatory properties have been established in a recent model system (15), and as demonstrated by a recent study, SpaC pilin is required for L. rhamnosus GG-induced cellular responses (16).…”