title: The Conserved Phenylalanine in the Transmembrane Domain Enhances Heteromeric Interactions of Syndecans.
abstract: The transmembrane domain (TMD) of the syndecans, a family of transmembrane heparin sulfate proteoglycans, is involved in forming homo- and heterodimers and oligomers that transmit signaling events. Recently, we reported that the unique phenylalanine in TMD positively regulates intramolecular interactions of syndecan-2. Besides the unique phenylalanine, syndecan-2 contains a conserved phenylalanine (SDC2-Phe-169) that is present in all syndecan TMDs, but its function has not been determined. We therefore investigated the structural role of SDC2-Phe-169 in syndecan TMDs. Replacement of SDC2-Phe-169 by tyrosine (S2F169Y) did not affect SDS-resistant homodimer formation but significantly reduced SDS-resistant heterodimer formation between syndecan-2 and -4, suggesting that SDC2-Phe-169 is involved in the heterodimerization/oligomerization of syndecans. Similarly, in an in vitro binding assay, a syndecan-2 mutant (S2(F169Y)) showed a significantly reduced interaction with syndecan-4. FRET assays showed that heteromolecular interactions between syndecan-2 and -4 were reduced in HEK293T cells transfected with S2(F169Y) compared with syndecan-2. Moreover, S2(F169Y) reduced downstream reactions mediated by the heterodimerization of syndecan-2 and -4, including Rac activity, cell migration, membrane localization of PKCα, and focal adhesion formation. The conserved phenylalanine in syndecan-1 and -3 also showed heterodimeric interaction with syndecan-2 and -4. Taken together, these findings suggest that the conserved phenylalanine in the TMD of syndecans is crucial in regulating heteromeric interactions of syndecans.
authors.affiliation: From the Department of Life Sciences, Research Center for Cellular Homeostasis, Ewha Womans University, Seoul 120-750, Korea and.
authors.forename: Mi-Jung
authors.initials: MJ
authors.lastname: Kwon
authors.affiliation: From the Department of Life Sciences, Research Center for Cellular Homeostasis, Ewha Womans University, Seoul 120-750, Korea and.
authors.forename: Jisu
authors.initials: J
authors.lastname: Park
authors.affiliation: the Seoul Center, Korea Basic Science Institute, Seoul 136-075, Korea.
authors.forename: Sinae
authors.initials: S
authors.lastname: Jang
authors.affiliation: the Seoul Center, Korea Basic Science Institute, Seoul 136-075, Korea.
authors.forename: Chi-Yong
authors.initials: CY
authors.lastname: Eom
authors.affiliation: From the Department of Life Sciences, Research Center for Cellular Homeostasis, Ewha Womans University, Seoul 120-750, Korea and OhES@ewha.ac.kr.
authors.forename: Eok-Soo
authors.initials: ES
authors.lastname: Oh
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002470:Cell Survival / Q000187:drug effects; D017124:Conserved Sequence; D057809:HEK293 Cells; D006801:Humans; D008969:Molecular Sequence Data; D010649:Phenylalanine / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects; D055503:Protein Multimerization; D017434:Protein Structure, Tertiary; D051381:Rats; D012967:Sodium Dodecyl Sulfate / Q000494:pharmacology; D053667:Syndecans / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D053667:Syndecans; D012967:Sodium Dodecyl Sulfate; D010649:Phenylalanine
keywords: heterodimerization; oligomerization; receptor regulation; signal transduction; syndecan; transmembrane domain