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Polycystin-1 Interacting Protein-1 (CU062) Interacts with the Ectodomain of Polycystin-1 (PC1)
Wendy A Lea1, Thomas Winklhofer1, Lesya Zelenchuk1
1Department of Nephrology and Hypertension, The Jared Grantham Kidney Institute, University of Kansas Medical Center, Kansas City, 3901 Rainbow Blvd., Mail Stop 3018, KS 66160, USA.
Insights
Autosomal dominant polycystic kidney disease (ADPKD) involves mutations in the PKD1 gene. Researchers identified CU062 as a potential polycystin complex component, potentially involved in clearing damaged mitochondria in ADPKD.
Area of Science:
- Cell Biology
- Molecular Biology
- Genetics
Background:
- Autosomal dominant polycystic kidney disease (ADPKD) is primarily caused by mutations in the *PKD1* gene, encoding polycystin-1 (PC1).
- PC1 is found in urinary exosome-like vesicles (PKD-ELVs) and is reduced in individuals with *PKD1* mutations.
- Proteins co-localized with PC1 in PKD-ELVs, like polycystin-2 (PC2), may form a polycystin complex (PCC).
Purpose of the Study:
- To investigate the role of CU062, a protein found to be decreased in ADPKD PKD-ELVs, as a potential component of the polycystin complex (PCC).
- To examine the cellular localization and interactions of CU062 with PC1 and PC2 under various cellular conditions.
Main Methods:
- Label-free mass spectrometry to compare urinary PKD-ELVs from normal and ADPKD individuals.
- Immunofluorescence (IF) microscopy to study the co-localization of CU062, PC1, and PC2.
- Cellular manipulation using mitochondrion-decoupling agents and induction of contact inhibition and mitochondrial stress.
Main Results:
- CU062 was identified as a candidate PCC component, decreased in ADPKD PKD-ELVs.
- CU062, PC1, and PC2 co-localized near focal adhesions, retraction fibers, and migrasomes in nonconfluent cells.
- In confluent cells, these proteins were found on extracellular vesicles associated with primary cilia.
- Under mitochondrial stress, PC1, PC2, and CU062 formed reticular networks on large, apically budding extracellular vesicles, potentially involved in extruding damaged mitochondria.
Conclusions:
- CU062 interacts with PC1 and may be a component of the polycystin complex (PCC).
- The study suggests a role for CU062 in identifying and extruding senescent mitochondria via extracellular vesicles in ADPKD.
- These findings offer new insights into the molecular mechanisms underlying ADPKD pathogenesis.
Abstract:
The PKD1 gene, encoding protein polycystin-1 (PC1), is responsible for 85% of cases of autosomal dominant polycystic kidney disease (ADPKD). PC1 has been shown to be present in urinary exosome-like vesicles (PKD-ELVs) and lowered in individuals with germline PKD1 mutations. A label-free mass spectrometry comparison of urinary PKD-ELVs from normal individuals and those with PKD1 mutations showed that several proteins were reduced to a degree that matched the decrease observed in PC1 levels. Some of these proteins, such as polycystin-2 (PC2), may be present in a higher-order multi-protein assembly with PC1-the polycystin complex (PCC). CU062 (Q9NYP8) is decreased in ADPKD PKD-ELVs and, thus, is a candidate PCC component. CU062 is a small glycoprotein with a signal peptide but no transmembrane domain and can oligomerize with itself and interact with PC1. We investigated the localization of CU062 together with PC1 and PC2 using immunofluorescence (IF). In nonconfluent cells, all three proteins were localized in close proximity to focal adhesions (FAs), retraction fibers (RFs), and RF-associated extracellular vesicles (migrasomes). In confluent cells, primary cilia had PC1/PC2/CU062 + extracellular vesicles adherent to their plasma membrane. In cells exposed to mitochondrion-decoupling agents, we detected the development of novel PC1/CU062 + ring-like structures that entrained swollen mitochondria. In contact-inhibited cells under mitochondrial stress, PC1, PC2, and CU062 were observed on large, apically budding extracellular vesicles, where the proteins formed a reticular network on the membrane. CU062 interacts with PC1 and may have a role in the identification of senescent mitochondria and their extrusion in extracellular vesicles.
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