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.
Boehm
M
M
Cell Biology and Metabolism Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
Aguilar
R C
RC
Bonifacino
J S
JS
D020727:ADP-Ribosylation Factors / Q000378:metabolism*; D033942:Adaptor Proteins, Vesicular Transport; D001665:Binding Sites; D020126:Brefeldin A / Q000494:pharmacology; D002352:Carrier Proteins / Q000737:chemistry* / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D006056:Golgi Apparatus / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D015151:Immunoblotting; D008565:Membrane Proteins / Q000737:chemistry* / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D011233:Precipitin Tests; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D015398:Signal Transduction; D014162:Transfection; D020798:Two-Hybrid System Techniques
D033942:Adaptor Proteins, Vesicular Transport; D002352:Carrier Proteins; D008565:Membrane Proteins; D020126:Brefeldin A; D020727:ADP-Ribosylation Factors