RESUMO
GCC185 is a long coiled-coil protein localized to the trans-Golgi network (TGN) that functions in maintaining Golgi structure and tethering mannose 6-phosphate receptor (MPR)-containing transport vesicles en route to the Golgi. We report the identification of two distinct domains of GCC185 needed either for Golgi structure maintenance or transport vesicle tethering, demonstrating the independence of these two functions. The domain needed for vesicle tethering binds to the clathrin adaptor AP-1, and cells depleted of GCC185 accumulate MPRs in transport vesicles that are AP-1 decorated. This study supports a previously proposed role of AP-1 in retrograde transport of MPRs from late endosomes to the Golgi and indicates that docking may involve the interaction of vesicle-associated AP-1 protein with the TGN-associated tethering protein GCC185.
Assuntos
Complexo 1 de Proteínas Adaptadoras/metabolismo , Complexo de Golgi/fisiologia , Proteínas de Membrana/metabolismo , Transporte Proteico/fisiologia , Vesículas Transportadoras/fisiologia , Animais , Bovinos , Linhagem Celular , Chlorocebus aethiops , Células Epiteliais/metabolismo , Complexo de Golgi/patologia , Proteínas da Matriz do Complexo de Golgi , Células HeLa , Humanos , Proteínas de Membrana/genética , Microscopia de Fluorescência , Proteínas Associadas aos Microtúbulos/metabolismo , Ligação Proteica/fisiologia , Domínios e Motivos de Interação entre Proteínas/fisiologia , RNA Interferente Pequeno/genética , Receptor IGF Tipo 2/metabolismo , Deleção de Sequência/fisiologia , Transfecção , Proteínas de Transporte Vesicular/metabolismo , Rede trans-Golgi/fisiologiaRESUMO
Core binding factor (CBF) participates in specification of the hematopoietic stem cell and functions as a critical regulator of hematopoiesis. Translocation or point mutation of acute myeloid leukemia 1 (AML1)/RUNX1, which encodes the DNA-binding subunit of CBF, plays a central role in the pathogenesis of acute myeloid leukemia and myelodysplasia. We characterized the t(X;21)(p22.3;q22.1) in a patient with myelodysplasia that fuses AML1 in-frame to the novel partner gene FOG2/ZFPM2. The reciprocal gene fusions AML1-FOG2 and FOG2-AML1 are both expressed. AML1-FOG2, which fuses the DNA-binding domain of AML1 to most of FOG2, represses the transcriptional activity of both CBF and GATA1. AML1-FOG2 retains a motif that recruits the corepressor C-terminal binding protein (CtBP) and these proteins associate in a protein complex. These results suggest a central role for CtBP in AML1-FOG2 transcriptional repression and implicate coordinated disruption of the AML1 and GATAdevelopmental programs in the pathogenesis of myelodysplasia.