ARL13B, PDE6D, and CEP164 form a functional network for INPP5E ciliary targeting

Area of Science:

• Cell Biology
• Genetics
• Molecular Biology

Background:

• Ciliary components mutations cause human genetic disorders known as ciliopathies, including Joubert syndrome (JBTS) and nephronophthisis (NPHP).
• Ciliopathy proteins form functional networks essential for primary cilium structure and maintenance.
• Mechanisms of ciliary protein targeting and specific protein functions remain incompletely understood.

Purpose of the Study:

• To elucidate the protein-protein interaction network of inositol polyphosphate-5-phosphatase E (INPP5E), a JBTS-associated protein.
• To investigate the mechanisms underlying INPP5E's targeting to primary cilia.
• To identify novel functional relationships between ciliopathy proteins.

Main Methods:

• Protein-protein interaction studies.
• Genetic analyses.
• Analysis of protein targeting motifs and interactions with known ciliary proteins.

Main Results:

• INPP5E is targeted to primary cilia via a C-terminal motif and prenyl-binding protein phosphodiesterase 6D (PDE6D).
• ADP-ribosylation factor-like 13B (ARL13B) facilitates INPP5E ciliary targeting, and JBTS-causing ARL13B mutations disrupt this interaction.
• A distinct functional network of ARL13B, INPP5E, PDE6D, and centrosomal protein 164 (CEP164) involved in JBTS and NPHP was identified, independent of previously defined NPHP and Meckel-Gruber syndrome (MKS) protein networks.

Conclusions:

• ARL13B, INPP5E, PDE6D, and CEP164 form a novel functional module critical for primary cilia.
• This network plays a role in JBTS and NPHP pathogenesis.
• Understanding these specific protein interactions advances knowledge of ciliopathy mechanisms.