PDE6D Mediates Trafficking of Prenylated Proteins NIM1K and UBL3 to Primary Cilia

Area of Science:

• Cell Biology
• Genetics
• Ophthalmology

Background:

• Mutations in phosphodiesterase 6D (PDE6D) disrupt prenylated protein transport to the ciliary membrane.
• PDE6D dysfunction leads to Joubert Syndrome (JBTS22) and mouse retinal degeneration.
• Understanding PDE6D's cargo is crucial for elucidating disease mechanisms.

Purpose of the Study:

• To identify and characterize the prenylated cargo of PDE6D using affinity proteomics.
• To investigate the role of novel PDE6D-interacting proteins in ciliopathies and retinal degeneration.
• To explore the function of ubiquitin-like protein 3 (UBL3) in photoreceptor cilia.

Main Methods:

• Affinity proteomics was employed to purify and identify PDE6D-interacting proteins.
• Immunofluorescence microscopy was used to determine the localization of identified proteins.
• Prenylation-dependent localization assays were performed for key cargo proteins.

Main Results:

• A set of PDE6D-interacting proteins involved in photoreceptor integrity, GTPase activity, nuclear import, and ubiquitination were identified.
• Novel ciliary cargo proteins, including FAM219A, serine/threonine-protein kinase NIM1 (NIM1K), and ubiquitin-like protein 3 (UBL3), were discovered.
• NIM1K and UBL3 exhibit prenylation-dependent localization within cilia, with UBL3 also found in vesicle-like structures and specific photoreceptor cilium compartments.

Conclusions:

• PDE6D interacts with proteins crucial for photoreceptor function and ciliogenesis.
• UBL3 is a prenylation-dependent ciliary cargo of PDE6D, potentially involved in protein sorting to the photoreceptor outer segment.
• These findings provide insights into the molecular basis of PDE6D-associated retinal degeneration.