PT  - JOURNAL ARTICLE
AU  - Oosterheert, Wout
AU  - Xenaki, Katerina T
AU  - Neviani, Viviana
AU  - Pos, Wouter
AU  - Doulkeridou, Sofia
AU  - Manshande, Jip
AU  - Pearce, Nicholas M
AU  - Kroon-Batenburg, Loes MJ
AU  - Lutz, Martin
AU  - van Bergen en Henegouwen, Paul MP
AU  - Gros, Piet
TI  - Implications for tetraspanin-enriched microdomain assembly based on structures of CD9 with EWI-F
AID  - 10.26508/lsa.202000883
DP  - 2020 Nov 01
TA  - Life Science Alliance
PG  - e202000883
VI  - 3
IP  - 11
4099  - http://www.life-science-alliance.org/content/3/11/e202000883.short
4100  - http://www.life-science-alliance.org/content/3/11/e202000883.full
SO  - Life Sci. Alliance2020 Nov 01; 3
AB  - Tetraspanins are eukaryotic membrane proteins that contribute to a variety of signaling processes by organizing partner-receptor molecules in the plasma membrane. How tetraspanins bind and cluster partner receptors into tetraspanin-enriched microdomains is unknown. Here, we present crystal structures of the large extracellular loop of CD9 bound to nanobodies 4C8 and 4E8 and, the cryo-EM structure of 4C8-bound CD9 in complex with its partner EWI-F. CD9–EWI-F displays a tetrameric arrangement with two central EWI-F molecules, dimerized through their ectodomains, and two CD9 molecules, one bound to each EWI-F transmembrane helix through CD9-helices h3 and h4. In the crystal structures, nanobodies 4C8 and 4E8 bind CD9 at loops C and D, which is in agreement with the 4C8 conformation in the CD9–EWI-F complex. The complex varies from nearly twofold symmetric (with the two CD9 copies nearly anti-parallel) to ca. 50° bent arrangements. This flexible arrangement of CD9–EWI-F with potential CD9 homo-dimerization at either end provides a “concatenation model” for forming short linear or circular assemblies, which may explain the occurrence of tetraspanin-enriched microdomains.