Interactions of GGA3 with the ubiquitin sorting machinery.
The Golgi-localized, gamma-ear-containing, Arf-binding (GGA) proteins constitute a family of clathrin adaptors that are mainly associated with the trans-Golgi network (TGN) and mediate the sorting of mannose 6-phosphate receptors. This sorting is dependent on the interaction of the VHS domain of the GGAs with acidic-cluster-dileucine signals in the cytosolic tails of the receptors. Here we demonstrate the existence of another population of GGAs that are associated with early endosomes. RNA interference (RNAi) of GGA3 expression results in accumulation of the cation-independent mannose 6-phosphate receptor and internalized epidermal growth factor (EGF) within enlarged early endosomes. This perturbation impairs the degradation of internalized EGF, a process that is normally dependent on the sorting of ubiquitinated EGF receptors (EGFRs) to late endosomes. Protein interaction analyses show that the GGAs bind ubiquitin. The VHS and GAT domains of GGA3 are responsible for this binding, as well as for interactions with TSG101, a component of the ubiquitin-dependent sorting machinery. Thus, GGAs may have additional roles in sorting of ubiquitinated cargo.
Puertollano
Rosa
R
Cell Biology and Metabolism Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA.
Bonifacino
Juan S
JS
D020727:ADP-Ribosylation Factors / Q000235:genetics / Q000378:metabolism*; D033942:Adaptor Proteins, Vesicular Transport; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D004705:Endocytosis / Q000502:physiology*; D011992:Endosomes / Q000378:metabolism*; D004815:Epidermal Growth Factor / Q000378:metabolism; D066246:ErbB Receptors / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D011485:Protein Binding / Q000502:physiology; D017434:Protein Structure, Tertiary / Q000502:physiology; D021381:Protein Transport / Q000502:physiology; D034622:RNA Interference; D017527:Receptor, IGF Type 2 / Q000378:metabolism; D025801:Ubiquitin / Q000378:metabolism*
D033942:Adaptor Proteins, Vesicular Transport; D002352:Carrier Proteins; C407306:GGA adaptor proteins; D017527:Receptor, IGF Type 2; D025801:Ubiquitin; D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D020727:ADP-Ribosylation Factors