Rab8 and TNPO1 function as the ciliary transport adapters for GPCRs

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• Primary cilia are crucial sensory organelles requiring specific protein localization.
• G-protein-coupled receptors (GPCRs) are essential transmembrane receptors found in cilia.
• Mechanisms for ciliary targeting of GPCRs are not fully understood.

Purpose of the Study:

• To investigate the role of Rab8 and TNPO1 as ciliary transport adaptors for GPCRs.
• To identify specific GPCRs that interact with Rab8 and TNPO1.
• To elucidate the ciliary targeting sequences (CTSs) within GPCRs.

Main Methods:

• Screening of nine cilium-localized GPCRs for interaction with Rab8 and TNPO1.
• Analysis of ciliary localization dependence on Rab8 and TNPO1.
• Identification and characterization of Ciliary Targeting Sequences (CTSs) in ADRB2.

Main Results:

• Five out of nine screened GPCRs interact with Rab8 and TNPO1.
• These five GPCRs require Rab8 and TNPO1 for ciliary localization.
• ADRB2 has two CTSs, with the C-terminal one mediating interaction with Rab8 and TNPO1.

Conclusions:

• Rab8 and TNPO1 serve as critical ciliary transport adaptors for a subset of GPCRs.
• The C-terminal tail of ADRB2 contains a functional CTS dependent on Rab8 and TNPO1.
• These findings advance understanding of GPCR trafficking to primary cilia.