Functional and physical interactions of the adaptor protein complex AP-4 with ADP-ribosylation factors (ARFs).

AP-4 is a member of the family of heterotetrameric adaptor protein (AP) complexes that mediate the sorting of integral membrane proteins in post-Golgi compartments. This complex consists of four subunits (epsilon, beta4, mu4 and sigma4) and localizes to the cytoplasmic face of the trans-Golgi network (TGN). Here, we show that ...
the recruitment of endogenous AP-4 to the TGN in vivo is regulated by the small GTP-binding protein ARF1. In addition, we demonstrate a direct interaction of the epsilon and mu4 subunits of AP-4 with ARF1. epsilon binds only to ARF1-GTP and requires residues in the switch I and switch II regions of ARF1. In contrast, mu4 binds equally well to the GTP- and GDP-bound forms of ARF1 and is less dependent on switch I and switch II residues. These observations establish AP-4 as an ARF1 effector and suggest a novel mode of interaction between ARF1 and an AP complex involving both constitutive and regulated interactions.
Mesh Terms:
ADP-Ribosylation Factors, Adaptor Proteins, Vesicular Transport, Binding Sites, Brefeldin A, Carrier Proteins, Cell Membrane, Golgi Apparatus, Hela Cells, Humans, Immunoblotting, Membrane Proteins, Microscopy, Fluorescence, Models, Biological, Mutagenesis, Site-Directed, Mutation, Precipitin Tests, Protein Binding, Protein Structure, Tertiary, Signal Transduction, Transfection, Two-Hybrid System Techniques
EMBO J.
Date: Nov. 15, 2001
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