Background <p>Aortic dissection (AD) is a life-threatening vascular disorder characterized by medial degeneration and phenotypic switching of vascular smooth muscle cells (VSMCs). While integrin subunit alpha 5 (ITGA5) has been implicated in VSMC plasticity, the upstream molecular mechanisms governing its regulation remain poorly defined.</p> Methods <p>Publicly available transcriptomic datasets were analyzed using differential expression analysis and WGCNA to identify hub genes associated with AD. The UbiBrowser database was employed to predict potential E3 ubiquitin ligases targeting ITGA5. In vitro, human aortic smooth muscle cells (HASMCs) were stimulated with Angiotensin II to mimic pathological conditions, and subjected to gain and loss-of-function assays, protein stability analysis, and co-immunoprecipitation in combination with HEK-293T cells. A BAPN-induced AD mouse model was utilized to evaluate the in vivo studies. Protein and gene expression were assessed by Western blotting, qPCR, and immunofluorescence.</p> Results <p>ITGA5 promoted the phenotypic switch of HASMCs toward a synthetic/inflammatory state. Deltex E3 ubiquitin ligase 1 (DTX1) directly interacted with ITGA5 and promoted its ubiquitination at lysine 137, leading to proteasome-dependent degradation. DTX1 overexpression suppressed ITGA5 levels, maintained contractile marker expression, and inhibited the synthetic/inflammatory phenotype of HASMCs. In vivo, DTX1 expression was downregulated and ITGA5 upregulated in BAPN-treated aortas, whereas DTX1 overexpression reduced ITGA5 levels, preserved medial integrity, and attenuated AD progression.</p> Conclusion <p>This study identifies DTX1 as a novel E3 ubiquitin ligase that promotes ITGA5 degradation, thereby maintaining the contractile phenotype of VSMCs and limiting AD progression. Targeting the DTX1–ITGA5 axis may offer a promising therapeutic approach for AD.</p>