ABSTRACT
Cells are dependent on correct sorting of activated receptor tyrosine kinases (RTKs) for the outcome of growth factor signaling. Upon activation, RTKs are coupled through the endocytic machinery for degradation or recycled to the cell surface. However, the molecular mechanisms governing RTK recycling are poorly understood. Here, we show that Golgi-localized gamma ear-containing Arf-binding protein 3 (GGA3) interacts selectively with the Met/hepatocyte growth factor RTK when stimulated, to sort it for recycling in association with "gyrating" clathrin. GGA3 loss abrogates Met recycling from a Rab4 endosomal subdomain, resulting in pronounced trafficking of Met toward degradation. Decreased Met recycling attenuates ERK activation and cell migration. Met recycling, sustained ERK activation, and migration require interaction of GGA3 with Arf6 and an unexpected association with the Crk adaptor. The data show that GGA3 defines an active recycling pathway and support a broader role for GGA3-mediated cargo selection in targeting receptors destined for recycling.
Subject(s)
Adaptor Proteins, Vesicular Transport/metabolism , Cell Movement , Endocytosis/physiology , Extracellular Signal-Regulated MAP Kinases/metabolism , Proto-Oncogene Proteins c-met/metabolism , ADP-Ribosylation Factor 6 , ADP-Ribosylation Factors/genetics , ADP-Ribosylation Factors/metabolism , Adaptor Proteins, Vesicular Transport/antagonists & inhibitors , Adaptor Proteins, Vesicular Transport/genetics , Animals , Blotting, Western , COS Cells , Cell Membrane/metabolism , Cells, Cultured , Chlorocebus aethiops , Endosomes , Extracellular Signal-Regulated MAP Kinases/genetics , Humans , Protein Transport , Proto-Oncogene Proteins c-crk/genetics , Proto-Oncogene Proteins c-crk/metabolism , Proto-Oncogene Proteins c-met/genetics , RNA, Messenger/genetics , RNA, Small Interfering/genetics , Reverse Transcriptase Polymerase Chain Reaction , Signal Transduction , rab4 GTP-Binding Proteins/genetics , rab4 GTP-Binding Proteins/metabolismABSTRACT
Natural killer (NK) cells are thought to develop from common lymphoid progenitors in the bone marrow. However, immature thymocytes also retain NK potential. Currently, the contribution of the thymus-dependent pathway in normal steady-state NK-cell development is unknown. Here, we show that TCRgamma genes are rearranged in approximately 5% of neonatal and 1% of adult mouse splenic NK cells, and similar levels are detected in NK cells from TCRbeta,delta double-knockout mice, excluding the possibility of T-cell contamination. NK-cell TCRgamma gene rearrangement is thymus dependent because this rearrangement is undetectable in nude mouse NK cells. These results change the current view of NK-cell development and show that a subset of NK cells develops from immature thymocytes that have rearranged TCRgamma genes.
