Background/aims: Cell-matrix interactions influence intestinal epithelial biology, but the whether specific integrin heterodimers exert different effects is unclear.
Methods: We used functional antibodies to investigate effects of the alpha2, alpha3, alpha5, and alpha6 integrin subunits on proliferation and differentiation of human intestinal Caco-2 cells on laminin. Cells seeded onto laminin-coated inserts in defibronectinized medium were treated with functional antibodies or normal IgG for 72 hrs and proliferation, alkaline phosphatase and dipeptidyl dipeptidase specific activity were measured.
Results: Caco-2 adhesion to antibody to each alpha-integrin subunit stimulated tyrosine phosphorylation of Focal Adhesion Kinase and paxillin, suggesting that these antibodies intiate integrin-related tyrosine signalling. Proliferation was inhibited by anti-alpha2 and anti-alpha3, but stimulated by anti-alpha6. Alkaline phosphatase and dipeptidyl dipeptidase specific activity were promoted by alpha2 blockade but decreased after a6 blockade. Proliferative blockade using mitomycin C or hydroxyurea prevented the effects of alpha2 ligation on differentiation, but the decrease in alkaline phosphatase specific activity observed after a6 integrin subunit blockade was preserved even after proliferative blockade.
Conclusion: lntegrin heterodimers modulate human Caco-2 intestinal epithelial biology on laminin in an alpha-subunit specific manner. The different effects of anti-alpha2 and anti-alpha6 may reflect competitition by these antibodies with integrin subunit interactions with laminin as well as initiation of their own signals or different functions for the alpha6 integrin subunit