title: EphA8-ephrinA5 signaling and clathrin-mediated endocytosis is regulated by Tiam-1, a Rac-specific guanine nucleotide exchange factor.
abstract: Recent studies indicate that endocytosis of Eph-ephrin complexes may be one of the mechanisms by which a high affinity cell-cell adhesion is converted to a repulsive interaction. In this study, we show that EphA8 undergoes clathrin-mediated endocytosis upon treatment with ephrin-A5, and that EphA8 is associated tightly with Tiam-1, a Rac-specific guanine nucleotide exchange factor. Analysis of EphA8 deletion mutants revealed that a juxtamembrane region in EphA8 is critically involved in endocytosis of EphA8-ephrinA5 complexes. An EphA8 mutant lacking this juxtamembrane portion was defective for endocytosis with ephrinA5, and also displayed a weak association with Tiam-1. Expression of an endocytosis-defective version of EphA8 resulted in a low level of Rac activity in response to ephrin-A5 stimulation. More importantly, down-regulation of Tiam-1 resulted in inefficient endocytosis of EphA8-ephrinA5 complexes. These results suggest that Tiam-1 plays a role in clathrin-dependent endocytosis of EphA8-ephrinA5 complexes.
authors.affiliation: Department of Biological Science, Sookmyung Women's University, Seoul, 140-742, Korea.
authors.forename: Sooyeon
authors.initials: S
authors.lastname: Yoo
authors.forename: Jongdae
authors.initials: J
authors.lastname: Shin
authors.forename: Soochul
authors.initials: S
authors.lastname: Park
mesh_terms: D008841:Actin Cytoskeleton / Q000201:enzymology; D002448:Cell Adhesion; D002461:Cell Line, Transformed; D002966:Clathrin / Q000378:metabolism; D004705:Endocytosis / Q000187:drug effects / Q000235:genetics; D004789:Enzyme Activation / Q000187:drug effects / Q000235:genetics; D036386:Ephrin-A5 / Q000494:pharmacology; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D011485:Protein Binding / Q000187:drug effects / Q000235:genetics; D017434:Protein Structure, Tertiary / Q000235:genetics; D036143:Receptor, EphA8 / Q000235:genetics / Q000378:metabolism*; D017384:Sequence Deletion / Q000235:genetics; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D000075684:T-Lymphoma Invasion and Metastasis-inducing Protein 1; D020744:rac GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D002966:Clathrin; D036386:Ephrin-A5; D020662:Guanine Nucleotide Exchange Factors; D000075684:T-Lymphoma Invasion and Metastasis-inducing Protein 1; C087334:TIAM1 protein, human; D036143:Receptor, EphA8; D020744:rac GTP-Binding Proteins