Kidney Week

Abstract: SA-PO631

Identification of Pathogenetic Pathways in Autosomal Dominant Tubulointerstitial Kidney Disease Due to Mutations in REN

Session Information

• Genetic Kidney Diseases: Models, Mechanisms, and Therapies
  October 26, 2024 | Location: Exhibit Hall, Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Genetic Diseases of the Kidneys

• 1202 Genetic Diseases of the Kidneys: Non-Cystic

Authors

• Schaeffer, Celine, IRCCS Ospedale San Raffaele, Milano, Italy

Celine Schaeffer, PhD

• De Fusco, Maurizio, IRCCS Ospedale San Raffaele, Milano, Italy

Maurizio De Fusco

• Pasqualetto, Elena, IRCCS Ospedale San Raffaele, Milano, Italy

Elena Pasqualetto

• Scolari, Caterina, IRCCS Ospedale San Raffaele, Milano, Italy

Caterina Scolari, MSc

• Diprima, Santo, IRCCS Ospedale San Raffaele, Milano, Italy

Santo Diprima

• Izzi, Claudia, Universita degli Studi di Brescia, Brescia, Italy

Claudia Izzi, MD

• Scolari, Francesco, Universita degli Studi di Brescia, Brescia, Italy

Francesco Scolari, MD

• Rampoldi, Luca, IRCCS Ospedale San Raffaele, Milano, Italy

Luca Rampoldi, PhD

Group or Team Name

• Molecular Genetics of Renal Disorders Unit.

Background

Autosomal Dominant Tubulointerstitial Kidney Disease (ADTKD) is a rare genetic disorder leading to progressive chronic kidney disease. ADTKD is caused by mutations in different genes including REN encoding for renin. Renin is a secreted protein composed of 3 domains: the leader peptide allowing its insertion in the endoplasmic reticulum (ER), a pro-segment regulating its protease activity, and the mature part. Mutations in mature renin lead to ER retention of mutant protein and to a late onset disease, while mutations in the leader peptide, associated with defective ER translocation, and mutations in the pro-segment, accumulating in the ER-to-Golgi compartment, lead to early onset disease.

Methods

We used transiently and stably transfected cells to further investigate the effect of mutations on renin trafficking and performed RNA sequencing on cells expressing renin isoforms under an inducible Tet-ON promoter.

Results

We demonstrate an unprecedented effect of mutations in the leader peptide and pro-segment leading to full or partial mistargeting of mutated protein to mitochondria. The pre-pro sequence of renin, carrying mutation in either the leader peptide or the pro-segment, is necessary and sufficient to drive mitochondrial rerouting. In turn, this leads to mitochondrial import defect and mitochondria fragmentation. Transcriptome profiling of cells expressing mutant renin isoforms in the leader peptide (L16R, L16del), pro-segment (E48K) and mature part (L381P) clearly shows that mutants mislocalised to mitochondria induce similar cellular responses that are only partly overlapping with the ones observed for the ER retained mutant. Specific responses are consistent with the observed trafficking defect (i.e ER stress and Unfolded Protein Response for the ER retained mutant and signs of mitochondrial dysfunction in mutants misrouted to mitochondria). However, all mutants converge to the induction of similar stress molecules as CHOP.

Conclusion

Despite the different cellular phenotype (mitochondrial vs ER localisation) and the severity of the associated clinical features, all ADTKD renin mutations converge to similar kidney damage. We are currently investigating how this endpoint is reached starting from stress signals emerging from the ER and mitochondria.

Funding

• Private Foundation Support