title: Identification of MAGI-3 as a transforming growth factor-alpha tail binding protein.
abstract: The cytoplasmic domain of the transforming growth factor-alpha precursor (proTGFalpha) contains a C-terminal PSD-95/SAP90, Discs Large, and Zona Occludens-1 (PDZ) recognition motif (TVV). By yeast two-hybrid screening of a mouse embryo library, we have found that a third member of a family of PDZ-containing proteins, membrane associated guanylate kinase inverted-3 (MAGI-3), binds to TGFalpha's TVV. MAGI-3 is widely expressed in multiple mouse tissues, including brain. Immunolocalization showed that MAGI-3 and TGFalpha were colocalized in neurons in the cortex and dentate gyrus, as well as in ependymal cells and some astrocytes. In vitro, proTGFalpha bound the PDZ-1 domain of MAGI-3 and MAGI-2, but not MAGI-1. MAGI-3 and the 17-kDa cell surface form of proTGFalpha interact transiently in MDCK cells stably transfected with both MAGI-3 and human proTGFalpha cDNAs. MAGI-3 and wild-type proTGFalpha colocalize at the cell surface. In contrast, MAGI-3 forms a stable complex with membrane-fixed TGFalpha early in the secretory pathway and interacts with immature and cell surface forms of membrane-fixed TGFalpha. Overexpression of MAGI-3 resulted in increased levels of TGFalpha in the basolateral medium of polarized MDCK cells, suggesting that MAGI-3 has a role in efficient trafficking of TGFalpha to the cell surface in polarized epithelial cells.
authors.affiliation: Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232, USA.
authors.forename: Jeffrey L
authors.initials: JL
authors.lastname: Franklin
authors.forename: Kenta
authors.initials: K
authors.lastname: Yoshiura
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Dempsey
authors.forename: Galina
authors.initials: G
authors.lastname: Bogatcheva
authors.forename: Loice
authors.initials: L
authors.lastname: Jeyakumar
authors.forename: Katherine S
authors.initials: KS
authors.lastname: Meise
authors.forename: R Scott
authors.initials: RS
authors.lastname: Pearsall
authors.forename: David
authors.initials: D
authors.lastname: Threadgill
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Coffey
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D001921:Brain / Q000201:enzymology; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D018076:DNA, Complementary / Q000235:genetics; D004285:Dogs; D004847:Epithelial Cells / Q000201:enzymology; D051528:Guanylate Kinases; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009703:Nucleoside-Phosphate Kinase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011498:Protein Precursors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011506:Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D014162:Transfection; D016211:Transforming Growth Factor alpha / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020798:Two-Hybrid System Techniques
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D018076:DNA, Complementary; D011498:Protein Precursors; D011506:Proteins; D011993:Recombinant Fusion Proteins; D016211:Transforming Growth Factor alpha; C052268:protransforming growth factor alpha; D009703:Nucleoside-Phosphate Kinase; D051528:Guanylate Kinases; C405684:Magi2 protein, mouse