Trs20 is required for TRAPP III complex assembly at the PAS and its function in autophagy

Area of Science:

• Cell Biology
• Molecular Biology
• Genetics

Background:

• The TRAPP complex is a guanine-nucleotide exchange factor (GEF) for Ypt/Rab GTPases, regulating key cellular pathways.
• TRAPP I and TRAPP II are involved in the exocytic pathway, while TRAPP III functions in autophagy.
• Mutations in Sedlin, the human ortholog of Trs20, cause spondyloepiphyseal dysplasia tarda (SEDT).

Purpose of the Study:

• To investigate the role of Trs20 in TRAPP III assembly and autophagy.
• To determine if the SEDT-linked mutation Trs20-D46Y affects TRAPP III assembly.
• To elucidate Trs20's function as an adaptor protein in TRAPP complex assembly.

Main Methods:

• Recombinant protein association assays.
• Co-immunoprecipitation of TRAPP complexes.
• Live-cell colocalization studies.
• Analysis of autophagy in mutant cells.

Main Results:

• Trs20 is required for the association of Trs85 (TRAPP III subunit) with the TRAPP complex.
• The SEDT-linked Trs20-D46Y mutation impairs Trs85 association.
• Trs20 acts as a linker, recruiting core TRAPP to the pre-autophagosomal structure (PAS) via Trs85.
• Trs20 is essential for both selective and non-selective autophagy.

Conclusions:

• Trs20 functions as an adaptor protein, critical for the assembly of both TRAPP II and TRAPP III complexes.
• The SEDT-linked mutation in Trs20 disrupts TRAPP II and TRAPP III assembly, impacting cellular transport and autophagy.
• Trs20's role extends beyond TRAPP II, being essential for TRAPP III function in autophagy.