Treponema pallidum serine protease Tp0841 degrades ZO-1 and VE-cadherin to breach the vascular barrier and enable dissemination

Treponema pallidum subsp. pallidum ( T. pallidum ), the causative agent of syphilis, disseminates to distant organs by disrupting the vascular endothelial barrier, yet the underlying molecular mechanisms remain poorly understood. Here, we investigated the role of the serine protease Tp0841 in this process. Bioinformatics and immunofluorescence localized Tp0841 to the periplasmic space of T. pallidum . Recombinant Tp0841 (rTp0841) and a catalytically inactive mutant (rΔTp0841) were generated. rTp0841 exhibited no cytotoxicity toward human endothelial cells (HUVEC and hCMEC/D3). Nonetheless, it induced concentration- and time-dependent downregulation of the tight junction protein ZO-1 and the adherens junction protein VE-cadherin, leading to reduced transendothelial electrical resistance and increased permeability. Occludin expression was unaffected, and rΔTp0841 had no effect on any of these proteins. Molecular docking and in vitro cleavage assays confirmed that Tp0841 directly proteolytically processes ZO-1 and VE-cadherin. Collectively, these findings demonstrate that Tp0841 directly degrades ZO-1 and VE-cadherin to disrupt vascular barrier integrity, thereby facilitating bacterial dissemination. Tp0841 thus represents a previously unrecognized virulence determinant contributing to the systemic spread of T. pallidum .