Distinct isocomplexes of the TRAPP trafficking factor coexist inside human cells

Area of Science:

• Cell Biology
• Molecular Biology
• Protein Complex Organization

Background:

• The transport protein particle (TRAPP) complex is essential for vesicular transport between the endoplasmic reticulum (ER) and the Golgi apparatus.
• While yeast TRAPP composition is known, the organization of mammalian TRAPP remains largely uncharacterized.
• Understanding mammalian TRAPP is critical for elucidating ER-to-Golgi trafficking regulation.

Purpose of the Study:

• To investigate the composition and organization of the mammalian TRAPP complex.
• To identify novel protein interactions within the human TRAPP complex.
• To explore the functional implications of identified TRAPP components in ER-to-Golgi transport.

Main Methods:

• Employed a tandem affinity purification (TAP) approach to isolate and identify interacting proteins.
• Conducted protein interaction studies to confirm associations.
• Utilized gel filtration analysis to assess complex formation and size.

Main Results:

• Provided the first experimental evidence for the association of NIK/IKKbeta binding protein (NIBP) with Bet3 in mammalian cells.
• Identified two human paralogs of Trs33 (Trs33A and Trs33B) associated with Bet3.
• Demonstrated that both NIBP and Trs33 paralogs are integral components of the human TRAPP complex, potentially forming distinct isocomplexes.

Conclusions:

• The study elucidates key components of the mammalian TRAPP complex, including NIBP and Trs33 paralogs.
• Findings suggest the existence of at least two distinct human TRAPP isocomplexes.
• These isocomplexes likely play differential roles in regulating ER-to-Golgi vesicular transport.