M-cell surface beta1 integrin expression and invasin-mediated targeting of Yersinia pseudotuberculosis to mouse Peyer's patch M cells

Abstract

Quantitative analysis of Yersinia pseudotuberculosis infection of murine gut loops revealed that significantly more wild-type bacteria associated with Peyer's patch M cells than with dome enterocytes or goblet cells. An invasin-deficient mutant was significantly attenuated for M-cell invasion, while beta1 integrin expression was demonstrated in the apical membranes of M cells but not enterocytes. M-cell targeting by Yersinia pseudotuberculosis in vivo may, therefore, be mediated primarily by the interaction of invasin with cell surface beta1 integrins.

FIG. 1

CLSM images of mouse Peyer’s patch FAE incubated for 120 min with Y. pseudotuberculosis YPIII/pIB1 and dual stained for M cells (red) and bacteria (green). (a) Surface view. Several bacteria are adherent to M cells, and a single bacterium (arrow) is adherent to an enterocyte. At depths of 2 μm (b) and 6 μm (c), large numbers of bacteria are located within the M cells. (d) Invaded bacteria are present 16 μm below the FAE surface, at which depth the cell type initially entered cannot be determined. Bar, 10 μm.

FIG. 2

CLSM images of mouse Peyer’s patch FAE incubated for 60 min with Y. pseudotuberculosis YPIII/pIB1 and dual stained for M cells (a and c) and bacteria (b and d). (a and b) Surface views. (c and d) Images at 1 μm in depth. Bacteria are absent from the surface of this region of FAE (a and b). Bacterial invasion (d [arrows]) is accompanied by a redistribution of UEA1 binding sites in the subapical region of the cells, observed on a confocal optical section as rings of UEA1 staining around the invading bacteria (c [arrows]). Bar, 10 μm.

FIG. 3

SEM images of mouse Peyer’s patch FAE incubated for 60 min with Y. pseudotuberculosis YPIII/pIB1. Both images depict a central M cell surrounded by enterocytes (and part of a brush cell in panel b). The M cell in panel a lacks adherent bacteria and exhibits a normal surface morphology. In contrast, the association of large numbers of bacteria with the M cell in panel b is accompanied by disruption of the M-cell surface. Bars, 2 μm.

FIG. 4

CLSM images of mouse Peyer’s patch FAE dual stained for M cells (a) and β1 integrins (b and c). (a and b) Surface views. UEA1-stained M cells express β1 integrins in their apical membranes (stained cells in panels a and b), whereas β1 integrin expression is absent from the apical membranes of enterocytes (unstained cells in panels a and b). (c) At a depth of 2 μm, both M cells and enterocytes express β1 integrins in their lateral membranes. Bar, 10 μm.