TAX1BP3 Is a SUMOylated Nucleocytoplasmic Shuttling Protein and Protects Against Vascular Neointimal Hyperplasia

Neointimal hyperplasia is the major cause of significant vascular complications after arterial interventions. Despite the advancements in strategies such as drug-eluting stents to minimize neointimal hyperplasia, achieving consistently effective long-term outcomes remains a challenge. Protein-protein interactions mediated by PDZ (PSD-95, Discs-large, and ZO-1) domains are essential for numerous biological processes. However, little is known about the role of PDZ proteins in neointima formation. This study aims to explore the role of TAX1BP3 (Tax1 binding protein 3), a singular PDZ protein, in phenotypic switching of vascular smooth muscle cells (VSMCs) and its implication in neointimal hyperplasia.

Subcellular localization of TAX1BP3 was assessed in isolated VSMCs or arteries obtained from mice with neointima formation. TAX1BP3 mutants were constructed to study the role of SUMOylation on TAX1BP3 nucleocytoplasmic shuttling. VSMC-specific Tax1bp3 knockout mice were generated to determine the relevant phenotypes in a carotid artery wire injury model. RNA sequencing, assays for transposase-accessible chromatin using sequencing, computational prediction of complex structures, and coimmunoprecipitation were performed to elucidate the underlying molecular mechanisms. Adeno-associated virus-mediated Tax1bp3 gene delivery and nanoencapsulated-TAX1BP3 were employed to investigate the potential translational relevance.

TAX1BP3 exhibited dynamic nucleocytoplasmic shuttling during phenotypic switching of VSMCs. TAX1BP3 is SUMOylated at K116, and its SUMOylation is essential for maintaining the nuclear localization of TAX1BP3. Deficiency of TAX1BP3 facilitated the transition from a contractile to a synthetic phenotype and aggravated neointima formation after vascular injury in mice. The integration of RNA sequencing and an assay for transposase-accessible chromatin using sequencing unveiled that TAX1BP3 primarily regulated the cell cycle progression and cell proliferation of VSMCs through YAP-TEAD transcription activity. The computational prediction of TAX1BP3/YAP1 complex structures and protein interaction-related experiments revealed that TAX1BP3 and TEAD1 compete for binding to YAP through its TEAD binding domain (BD) in a noncanonical PDZ manner. AAV-mediated Tax1bp3 gene delivery significantly attenuated postinjury neointima formation and the progression of atherosclerosis. Nanoencapsulated-TAX1BP3 administration effectively reduced VSMC phenotypic switching and neointimal hyperplasia.

These results demonstrate that SUMOylation of TAX1BP3 at K116 enables its nucleocytoplasmic shuttling during phenotypic switching of VSMCs. TAX1BP3 competitively interacts with the YAP-TEAD complex in a noncanonical PDZ manner and exerts its protective role in vascular neointimal hyperplasia primarily through the regulation of cell proliferation.