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: SA-PO749

Oxysterol-Binding Protein Like 7 Deficiency Leads to Decreased Autophagic Flux, Increased Lipid Droplet Accumulation, and Apoptosis in Podocytes

Session Information

Category: Glomerular Diseases

  • 1304 Glomerular Diseases: Podocyte Biology

Authors

  • Pressly, Jeffrey D., University of Miami Katz Family Division of Nephrology and Hypertension, Miami, Florida, United States
  • Merscher, Sandra M., University of Miami Katz Family Division of Nephrology and Hypertension, Miami, Florida, United States
  • Fornoni, Alessia, University of Miami Katz Family Division of Nephrology and Hypertension, Miami, Florida, United States
Background

Previously we demonstrated that OSBPL7 protein levels are decreased in podocyte models of chronic kidney disease (CKD). OSBPs are involved in cholesterol transfer from the endoplasmic reticulum (ER) to the Golgi, cholesterol efflux, and autophagy. OSBPL7 is a lipid transfer protein that transfers cholesterol for PI4P at subcellular membrane sites that contains an oxysterol binding domain (OSBD), a PH domain, and an FFAT motive. It remains unknown if OSBPL7 deficiency contributes to dysregulated lipid trafficking, leading to a decrease in podocyte viability.

Methods

OSBPL7-V5 construct was purchased from Addgene, and mutated constructs carrying deletions in the FFAT and PH domains of OSBPL7 were generated by PCR mutagenesis. Overexpression of OSBPL7 (deletion) constructs was achieved using Fugene HD (Promega) following manufacturer-recommended transfection protocols. Whole-cell lysates were collected from siOSBPL7 and scOSBPL7 podocytes and analyzed for LC3 and GATE-16 protein expression by western blot. LD number was determined using Opera high content screening system and Columbus analysis software. Apoptosis was measured using the ApoTox-Glo Apoptosis Assay (Promega).

Results

OSBPL7 deficiency in siOSBPL7 podocytes leads to decreased autophagic flux with increased levels of LC3 cleavage and decreased levels of GATE-16. siOSBPL7 podocytes demonstrate increased lipid droplets compared to scOSBPL7 podocytes. Overexpression of full-length OSBPL7 is sufficient to protect siOSBPL7 podocytes from apoptosis. However, overexpression of an OSBPL7 construct with a deletion of the FFAT domain failed to rescue the effect on apoptosis, implicating the FFAT domain as imperative for the antiapoptotic effects of OSBPL7 in podocytes.

Conclusion

OSBPL7, i.e., the FFAT domain of OSBPL7, is necessary for the proper function of and viability of podocytes. OSBPL7 deficiency leads to decreased autophagic flux, lipid accumulation, and podocyte injury. The decreased autophagic flux may contribute to lipid droplet accumulation, resulting in lipotoxicity in podocytes deficient in OSBPL7. Future studies will address the role of OSBPL7 in lipophagy and the role of lipophagy in CKD, which may lead to the identification of novel therapeutic targets for the treatment of this prevalent and costly disease.

Funding

  • NIDDK Support