BACKGROUND

is a leading cause of contagious mastitis in dairy cattle. Internalization of by bovine mammary gland epithelial cells is thought to be responsible for persistent and chronic intramammary infection, but the underlying mechanisms are not fully understood.

METHODS

In the present study, we evaluated the role of Annexin A2 (AnxA2), a membrane-binding protein, in invasion into bovine mammary epithelial cell line (MAC-T). In vitro binding assays were performed to co-immunoprecipitate the binding proteins of AnxA2 in the lysates of .

RESULTS

AnxA2 mediated the internalization but not adherence of . Engagement of AnxA2 stimulated an integrin-linked protein kinase (ILK)/p38 MAPK cascade to induce invasion. One of the AnxA2-precipitated proteins was identified as clumping factor B (ClfB) through use of mass spectrometry. Direct binding of ClfB to AnxA2 was further confirmed by using a pull-down assay. Pre-incubation with recombinant ClfB protein enhanced internalization, an effect that was specially blocked by anti-AnxA2 antibody.

CONCLUSION

Our results demonstrate that binding of ClfB to AnxA2 has a function in promoting internalization. Targeting the interaction of ClfB and AnxA2 may confer protection against mastitis.