The Importance of LTA-induced Signal Transduction for the Mechanism of Marginal Keratitis
Kruse F. E.1, Schmitz M. L.2,Ebner S.1, Erber B.1, You L.1
1Department of Ophthalmology, Medical School, University of Heidelberg; 2Institute for Chemistry and Biochemistry, University of Bern/CH
Purpose: To understand the mechanism of marginal keratitis we seeked to further identify components of signal transduction pathways based on our earlier findings that suggest that the bacterial cell wall component lipoteichoic acid (LTA) might be important in this context.
Method: Human corneal keratocytes were cultured in the presence of LTA from Staphylococcus aureus. The transcription of a putative receptor (TLR 4) and MD-2, a TLR 4-associated protein to discriminate LTA, were detected by RT-PCR. The formation of TLR 4 and FAK complex were evaluated by coimmunoprecipitation and western blots. Components of map kinase signal transduction were investigated as well as expression of chemokines. Protein kinase inhibitors were used to identify LTA-induced signaling for the expression of chemokines.
Results: The transcription of TLR 4 and MD-2 was detectable in ex vivo corneal stroma and cultured keratocytes. The formation of TLR 4 and FAK complex is time-dependently induced by LTA and inhibited by herbimycin A. A systematic analysis of LTA-activated MAPK pathways revealed no significant effects on JNK and p38, but a dose-and time-dependent phosphorylation of members of the ERK pathway. Two specific tyrosine pho
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