ASN's Mission

To create a world without kidney diseases, the ASN Alliance for Kidney Health elevates care by educating and informing, driving breakthroughs and innovation, and advocating for policies that create transformative changes in kidney medicine throughout the world.

learn more

Contact ASN

1401 H St, NW, Ste 900, Washington, DC 20005

email@asn-online.org

202-640-4660

The Latest on Twitter

Kidney Week

Abstract: PO1253

Eliosin, a Protein Encoded by a Transcript from the HmPKD1 Locus, Is a Component of Mitochondria-Endoplasmic Reticulum Contact Sites (MAMs) and Repairs Mitochondria Fragmentation in Polycystic Kidney Disease 12-7 Cells

Session Information

Category: Genetic Diseases of the Kidneys

  • 1001 Genetic Diseases of the Kidneys: Cystic

Authors

  • Bacallao, Robert L., Indiana University School of Medicine, Indianapolis, Indiana, United States
  • Xu, Weimin, Indiana University School of Medicine, Indianapolis, Indiana, United States
  • Lazar, Virginie, Indiana University School of Medicine, Indianapolis, Indiana, United States
Background

The HmPKD1 gene locus is predicted to produce multiple transcripts whose functions are largely unknown. We studied one such alternative transcript that starts at intron 40 but has a protein start site in exon 41. This transcript has a splice from the 3’ end of exon 41 to the 5’ end of exon 43. Subsequent splices follow the same splicing pattern found in the full-length polycystin-1 mRNA. The subcellular localization and function of this alternative transcript is not known.

Methods

We made PCR primers designed to detect the unique splice features of the transcript which are not a feature of full-length HmpKD1 transcripts. RT-PCR studies were conducted to identify the alternative transcript. cDNA encoding the alternative transcript and its product (Eliosin) were expressed in COS-1, 293 and NIH 3T3 cells for immuneblot and light microscopy analysis.. Co-localization studies were performed between mCherry-Eliosin fusion protein and dynamin related protein-1 (DRP-1) or mitofusion-1 (MFN-1). Anallysis of mitochondria morphology in co-transfection studies was performed in 293 and PKD 12-7 cells.

Results

RT-PCR reactions performed using RNA from human kidney, confirmed that a shortened PCR fragment from the PKD1 gene's exons 41-43 is expressed. Immuneblot analysis revealed that the protein we named Eliosin is a 48 kDa protein and it is expressed by cDNA isolated from human testes. Flourescence microscopy studies show co-localization between Eliosin and inositol-3-phosphate receptor or MFN-1, known components of MAMs. However when Eliosin and DRP-1 are co-expressed, DRP-1 is found in the cytosol. Since DRP-1 mediates mitochondria scission we reasoned that it is the mutation in Eliosin that leads to unopposed mitochondria scission in PKD12-7 cells. We found that untransfected PKD 12-7 cells have fragmented mitochondria while Eliosin transfected PKD 12-7 have normal appearing mitochondria.

Conclusion

Eliosin is a 48 kDa protein that is expressed in human kidney. It is a component of mitochondria-ER membrane contact sites and it acts to displace dynamic related protein-1 from MAMs. Based on these findings we conclude that Eliosin plays a role in altering the balance between mitochondria fusion and scission. This finding extends the HmPKD1 locus role in mitochondria metabolic physiology.

Funding

  • Clinical Revenue Support