Hexa-Longin domain scaffolds for inter-Rab signalling

Area of Science:

• Molecular Biology
• Cell Biology
• Evolutionary Biology

Background:

• Primary cilia are essential cellular structures involved in development and tissue function.
• Defects in primary cilia assembly and maintenance lead to ciliopathies, a group of genetic disorders.
• The CPLANE protein complex plays a critical role in primary cilia formation and upkeep.

Purpose of the Study:

• To investigate the evolutionary relationships and structural features of proteins within the CPLANE complex.
• To identify novel protein-protein interactions and functional roles of CPLANE components.
• To understand the molecular mechanisms underlying ciliogenesis and its link to ciliopathies.

Main Methods:

• Comparative evolutionary analyses, including coevolution-based contact prediction and sequence conservation.
• Identification of homologous protein domains across different species and protein families.
• Bioinformatic analysis of protein structures and functional domains.

Main Results:

• The INTU/FUZ heterodimer was identified as a novel component of homologous Hermansky-Pudlak syndrome and MON1-CCZ1 (HerMon) complexes.
• Homologous Longin domains were found to be triplicated in six key proteins: MON1A, CCZ1, HPS1, HPS4, INTU, and FUZ.
• The findings suggest that the INTU/FUZ complex functions as a Guanine nucleotide Exchange Factor (GEF).

Conclusions:

• The INTU/FUZ heterodimer is a newly discovered member of the HerMon complex family.
• This complex likely acts as a GEF, regulating Rab GTPases during the activation process in ciliogenesis.
• The study provides new insights into the molecular machinery governing primary cilia formation and potential therapeutic targets for ciliopathies.