Figure 8. β1 integrin signalling specifies the orientation and maintenance of epithelial polarity and the formation of lumens.

(a) β1-integrin was ablated in MECs after acini had polarized and developed lumens. Note the inversion of polarity detected by (i) TRITC phalloidin and (ii) aPKC. Bar: 10 μm.

(b) Temporal sequence of how BM-integrin engagement remodel a neo-basolateral surface. i) Initially, cells are unpolarized with fragmented Golgi and apical markers at the membrane. ii) Engagement of β1-integrins with the BM first recruits ILK to instruct the orientation of polarity. Integrin/ILK then polarize MTs along the apico-basal axis by interacting with their plus ends followed by endocytosis of apical components from this surface. iii) Integrins/ ILK regulate internal cell polarity by positioning the Golgi apparatus sub-apically which further aids polarized trafficking to the membrane. A new apical face is established on the membrane opposing the BM, which subsequently leads to lumen formation.