Matriptase proteolysis selectively drives disassembly and internalization of the claudin-7 complex while preserving...

Claudin-7 is a basolaterally enriched tight junction protein that participates in membrane complexes with EpCAM and Trop-2, linking epithelial adhesion to barrier organization. Although proteolytic processing of EpCAM/Trop-2 has been proposed to regulate this complex, its functional consequences for claudin-7 remain unresolved. Here, we define the role of matriptase in regulating claudin-7 dynamics in HaCaT human keratinocytes. Under steady-state conditions, matriptase knockout had only modest effects on claudin-7 distribution, suggesting a limited role in initial complex formation. In contrast, induction of matriptase autoactivation by mildly acidic stress triggered rapid and pronounced remodeling of claudin-7 complex in parental cells. Claudin-7 underwent progressive redistribution from continuous junctional staining to discontinuous bar-like structures, followed by the appearance of abundant intracellular puncta consistent with endocytosed vesicles, ultimately leading to its removal from the cell surface. This dynamic process was temporally coordinated and accompanied by increased accessibility of the claudin-7 C-terminus, indicating disassembly of claudin-7 complexes. These changes were abolished in matriptase-deficient cells, in which claudin-7 remained stably associated with cell-cell interfaces and failed to internalize. Suppression of matriptase autoactivation by NaCl similarly prevented claudin-7 internalization, demonstrating that proteolytic activity is required for this process. Notably, adherens junctions remained largely intact with E-cadherin continuously localized at cell-cell interfaces. Collectively, these findings establish that matriptase proteolytic activity is essential for disassembly and internalization of claudin-7 complex. This work supports a model in which the EpCAM/Trop-2-claudin-7 axis functions as a protease-regulated membrane complex that dynamically modulates epithelial organization.