Abstract
Background: Staphylococcus aureus is a leading cause of contagious mastitis in dairy cattle. Internalization of S. aureus 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 S. aureus 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 S. aureus. Results: AnxA2 mediated the internalization but not adherence of S. aureus. Engagement of AnxA2 stimulated an integrin-linked protein kinase (ILK)/p38 MAPK cascade to induce S. aureus invasion. One of the AnxA2-precipitated proteins was identified as S. aureus 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 S. aureus 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 S. aureus internalization. Targeting the interaction of ClfB and AnxA2 may confer protection against S. aureus mastitis.
Highlights
Staphylococcus aureus is a major cause of infections in both human beings and a large number of animal species, including dairy cows
We focused on integrin-linked protein kinase (ILK), which is essential for S. aureus internalization [37,38], and p38 mitogen-activated protein kinase (MAPK), a member of MAPK
We demonstrate that Annexin A2 (AnxA2) is critical for S. aureus internalizaIn the present study, we demonstrate that AnxA2 is critical for S. aureus internalization tion into bovine mammary epithelial cells, and that ILK/p38 MAPK signal pathway is ininto bovine mammary epithelial cells, and that ILK/p38 MAPK signal pathway is involved volved in this process
Summary
Staphylococcus aureus is a major cause of infections in both human beings and a large number of animal species, including dairy cows. S. aureus is a leading cause of contagious mastitis (infection of the mammary gland) in cattle and strikes the greatest challenge in the dairy industry [2,3,4,5]. Staphylococcus aureus is a leading cause of contagious mastitis in dairy cattle. Internalization of S. aureus 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 S. aureus invasion into bovine mammary epithelial cell line (MAC-T). Pre-incubation with recombinant ClfB protein enhanced S. aureus internalization, an effect that was specially blocked by anti-AnxA2 antibody
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