RIN3: a novel Rab5 GEF interacting with amphiphysin II involved in the early endocytic pathway.
The small GTPase Rab5, which cycles between active (GTP-bound) and inactive (GDP-bound) states, plays essential roles in membrane budding and trafficking in the early endocytic pathway. However, the molecular mechanisms underlying the Rab5-regulated processes are not fully understood other than the targeting event to early endosomes. Here, we report a ... novel Rab5-binding protein, RIN3, that contains many functional domains shared with other RIN members and additional Pro-rich domains. RIN3 displays the same biochemical properties as RIN2, the stimulator and stabilizer of GTP-Rab5. In addition, RIN3 exhibits its unique intracellular localization. RIN3 expressed in HeLa cells localized to cytoplasmic vesicles and the RIN3-positive vesicles contained Rab5 but not the early endosomal marker EEA1. Transferrin appeared to be transported partly through the RIN3-positive vesicles to early endosomes. RIN3 was also capable of interacting via its Pro-rich domain with amphiphysin II, which contains SH3 domain and participates in receptor-mediated endocytosis. Interestingly, cytoplasmic amphiphysin II was translocated into the RIN3- and Rab5-positive vesicles when co-expressed with RIN3. These results indicate that RIN3 biochemically characterized as the stimulator and stabilizer for GTP-Rab5 plays an important role in the transport pathway from plasma membrane to early endosomes.
Mesh Terms:
Animals, Biological Transport, COS Cells, Carrier Proteins, Cells, Cultured, Cercopithecus aethiops, Cloning, Molecular, Cytoplasmic Vesicles, Endocytosis, Endosomes, Guanine Nucleotide Exchange Factors, Hela Cells, Humans, Membrane Fusion, Membrane Proteins, Microscopy, Confocal, Nerve Tissue Proteins, Protein Binding, Protein Structure, Tertiary, Two-Hybrid System Techniques, Vesicular Transport Proteins, rab5 GTP-Binding Proteins
Animals, Biological Transport, COS Cells, Carrier Proteins, Cells, Cultured, Cercopithecus aethiops, Cloning, Molecular, Cytoplasmic Vesicles, Endocytosis, Endosomes, Guanine Nucleotide Exchange Factors, Hela Cells, Humans, Membrane Fusion, Membrane Proteins, Microscopy, Confocal, Nerve Tissue Proteins, Protein Binding, Protein Structure, Tertiary, Two-Hybrid System Techniques, Vesicular Transport Proteins, rab5 GTP-Binding Proteins
J. Cell. Sci.
Date: Oct. 15, 2003
PubMed ID: 12972505
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