Kidney Week

Abstract: SA-PO1182

Distal Convoluted Tubule (DCT)-Specific Disruption of the COP9 Signalosome Induces Autophagy Leading to Kidney Injury and DCT Atrophy

Session Information

• CKD: Mechanisms - 3
  October 26, 2024 | Location: Exhibit Hall, Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: CKD (Non-Dialysis)

• 2303 CKD (Non-Dialysis): Mechanisms

Authors

• Cornelius, Ryan J., Oregon Health & Science University, Portland, Oregon, United States

Ryan J. Cornelius, PhD

• Su, Xiao-Tong, Oregon Health & Science University, Portland, Oregon, United States

Xiao-Tong Su, PhD

• Nelson, Jonathan W., University of Southern California Keck School of Medicine, Los Angeles, California, United States

Jonathan W. Nelson, PhD

• Ellison, David H., Oregon Health & Science University, Portland, Oregon, United States

David H. Ellison, MD, FASN

• Yang, Chao-Ling, Oregon Health & Science University, Portland, Oregon, United States

Chao-Ling Yang, MD

Background

Regulated maintenance of protein degradation is accomplished by two main systems: the ubiquitin-proteasome system and autophagy-lysosome system. Proteasomal degradation selectively ubiquitinates substrates via E3 ubiquitin ligases, the largest family of which are Cullin-RING ligases (CRLs). All CRLs are regulated by the COP9 signalosome (CSN), which interacts with the CRL to turn off ubiquitin ligase activity. To investigate the role of impaired CSN dysfunction in the kidney, we inactivated the CSN by deleting Jab1 (the key CSN catalytic subunit) along the entire nephron (KS-Jab1^-/-). The mice developed progressive kidney injury with specific atrophy of the distal convoluted tubule (DCT) that culminated in chronic kidney disease (CKD). Autophagy is known to be associated with exacerbating CKD and can be activated due to cellular stress. We hypothesized that CSN dysfunction activates autophagy leading to atrophy of the DCT and CKD.

Methods

Inducible DCT-specific NCC-Cre-ERT2 mice were bred to INTACT (Isolation of Nuclei TAgged in specific Cell Types, which fluorescently labels nuclei) and Jab1 floxed mice to generate DCT-INTACT-Jab1^-/- mice. At six-weeks nuclei from kidney cortex was isolated and the DCT was enriched using Fluorescence-Activated Nuclei Sorting (FANS). GFP-positive nuclei were used for single-nucleus RNA-sequencing (snRNA-seq). Additionally, we impaired the autophagy pathway utilizing Atg5 floxed mice to generate JAB1 and ATG5 double knock out mice (DCT-Jab1^-/-/Atg5^-/-).

Results

snRNA-seq of DCT enriched cells from DCT-INTACT-Jab1^-/- mice showed four distinct populations: DCT1, DCT2, damaged DCT1 (dDCT1), and damaged DCT2 (dDCT2) cells. The damaged DCT cells showed downregulation of Differentially Expressed Genes (DEGs) associated with ion transport and metabolic processes and upregulation of DEGs associated with apoptosis, which is known to activate autophagy. Like KS-Jab1^-/- mice, DCT-Jab1^-/- mice developed tubule injury and atrophy of the DCT. Inhibition of autophagy in DCT-Jab1^-/-/Atg5^-/- mice attenuated kidney injury and reduced DCT atrophy.

Conclusion

DCT-specific CSN disruption causes activation of apoptosis and autophagy pathways leading to tubule injury and atrophy of the DCT.

Funding

• NIDDK Support