| Summary: | Background: <i>Staphylococcus aureus</i> is a leading cause of contagious mastitis in dairy cattle. Internalization of <i>S. aureus</i> 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 <i>S. aureus</i> 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 <i>S. aureus</i>. Results: AnxA2 mediated the internalization but not adherence of <i>S. aureus</i>. Engagement of AnxA2 stimulated an integrin-linked protein kinase (ILK)/p38 MAPK cascade to induce <i>S. aureus</i> invasion. One of the AnxA2-precipitated proteins was identified as <i>S. aureus</i> 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 <i>S. aureus</i> 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 <i>S. aureus</i> internalization. Targeting the interaction of ClfB and AnxA2 may confer protection against <i>S. aureus</i> mastitis.
|
|---|