TRIM16 Mediates K63-Linked Ubiquitination of DAB2 to Facilitate Vascular Calcification.

Background: Vascular calcification is highly prevalent in patients with chronic kidney disease (CKD), and the underlying mechanisms remain elusive. Several studies have indicated an important role of protein ubiquitination in vascular calcification. However, the role of E3 ubiquitin ligases in vascular calcification remains poorly understood.

Methods: Calcification of vascular smooth muscle cells (VSMCs) was induced by high phosphate. CKD mouse model was induced by an adenine diet, and CKD rat model was established using 5/6 nephrectomy method. Adenovirus, siRNA (small interfering RNA), adeno-associated virus, and smooth muscle cell-specific TRIM16 (tripartite motif 16) knockout mice were used to investigate the role of TRIM16 in vascular calcification. Immunoprecipitation-mass spectrometry, and ubiquitination assay were used to dissect how TRIM16 regulates vascular calcification.

Results: Bioinformatic analysis suggested that E3 ubiquitin ligase TRIM16 could be a key modulator of vascular calcification. TRIM16 expression was increased during vascular calcification. Overexpression of TRIM16 exacerbated VSMC calcification and aortic calcification of CKD rats. By contrast, the knockdown of TRIM16 alleviated VSMC calcification and aortic calcification in CKD rats. Moreover, the deletion of TRIM16 inhibited VSMC calcification and aortic calcification in VitD3 (vitamin D3)-overloaded mice and CKD mice. Mechanistically, immunoprecipitation-mass spectrometry revealed that DAB2 (disabled homolog 2) was the potential downstream target of TRIM16. Coimmunoprecipitation showed that the SPRY (SPla and the RYanodine receptor) domain of TRIM16 interacted with the proline-rich domain of DAB2. Moreover, ubiquitination assay revealed that the SPRY domain of TRIM16 is required for TRIM16-mediated K63-linked ubiquitination of DAB2 at K656 residue. Of note, the knockdown of DAB2 inhibited TRIM16-induced VSMC calcification. Furthermore, knockdown of DAB2 antagonized endocytosis of integrin β1 and subsequent activation of FAK (focal adhesion kinase)-STAT3 (signal transduction and transcriptional activation factor 3) signaling induced by overexpression of TRIM16.

Conclusions: Our study for the first time demonstrates that E3 ubiquitin ligase TRIM16 catalyzes K63-ubiquitination of the endocytic adaptor DAB2, leading to endocytosis of integrin β1 and activation of FAK-STAT3 signaling, and subsequently exacerbates vascular calcification, suggesting that TRIM16-DAB2 axis is a promising therapeutic target for vascular calcification.