<i>Treponema pallidum</i> Protein Tp0136 Induces Spheroidization of Vascular Endothelial Cells, Resulting in Widened Intercellular Junctions and Enhanced Vascular Permeability

The <i>Treponema pallidum</i> membrane protein Tp0136 facilitates <i>Treponema pallidum</i> dissemination, and the permeability of vasculature is intricately linked to the density of the vascular endothelial barrier, which is strongly associated with the morphology of vascular endothelial cells. In this study, utilizing the approach of inoculating Tp0136 recombinant protein into the skin lesions of rabbits infected with <i>Treponema pallidum</i>, it was observed that the Tp0136 recombinant protein induced spheroidization of vascular endothelial cells and enlargement of intercellular junctions. By high-throughput RNA sequencing, the upregulation of the RNA-binding protein cysteine- and glycine-rich protein 1 (CSRP1) is identified, which modulated the alternative splicing of exon 19 of myosin X (MYO10), which in turn downregulated the expression of MYO10, ultimately inducing morphological spheroidization in vascular endothelial cells. Using CSRP1-specific shRNA to knock down CSRP1 or using the alternative splicing inhibitor, the spheroidized vascular endothelial cells revert to a flattened state, suggesting that Tp0136 regulates the alternative splicing of MYO10 through CSRP1, leading to a downregulation of MYO10, followed by the spheroidization of vascular endothelial cells and an enlargement of intercellular junctions. These findings contribute to elucidating a mechanism underlying the dissemination of <i>Treponema pallidum</i>.