Fibronectin tetrapeptide is target for syphilis spirochete cytadherence

Area of Science:

• Microbiology
• Cell Biology
• Biochemistry

Background:

• * *Treponema pallidum*, the causative agent of syphilis, adheres to host cells.
• * Fibronectin (Fn) on host cell surfaces is crucial for this adhesion.
• * The cell-binding domain of Fn contains a key arg-gly-asp-ser (RGDS) sequence.

Purpose of the Study:

• * To investigate the role of the RGDS sequence in *T. pallidum* host cell attachment.
• * To determine if synthetic peptides mimicking the RGDS sequence can inhibit this interaction.

Main Methods:

• * Used a synthetic heptapeptide (GRGDSPC) containing the RGDS sequence.
• * Assessed the peptide's ability to compete with radiolabeled Fn binding to *T. pallidum*.
• * Evaluated the peptide's effect on *T. pallidum* attachment to HEp-2 and HT1080 cell monolayers.
• * Tested control heptapeptides with altered RGDS sequences.

Main Results:

• * The GRGDSPC heptapeptide specifically inhibited the binding of Fn to *T. pallidum*.
• * This peptide also reduced *T. pallidum* attachment to host cell monolayers.
• * Heptapeptides with modifications in the RGDS sequence did not inhibit Fn binding or bacterial attachment.

Conclusions:

• * *T. pallidum* utilizes the RGDS sequence on fibronectin for host cell attachment.
• * This mechanism is similar to how eukaryotic cells bind to fibronectin.
• * The RGDS sequence is a critical determinant of *T. pallidum* cytadherence.