Hierarchy of merlin and ezrin N- and C-terminal domain interactions in homo- and heterotypic associations and their relationship to binding of scaffolding proteins EBP50 and E3KARP.
The neurofibromatosis 2 tumor suppressor gene product merlin has strong sequence identity to the ezrin-radixin-moesin (ERM) family over its approximately 300-residue N-terminal domain. ERM proteins are membrane cytoskeletal linkers that are negatively regulated by an intramolecular association between domains known as NH(2)- and COOH-ERM association domains (N- and C-ERMADs) that mask sites for binding membrane-associated proteins, such as EBP50 and E3KARP, and F-actin. Here we show that merlin has self-association regions analogous to the N- and C-ERMADs. Moreover, the N-/C-ERMAD interaction in merlin is relatively weak and dynamic, and this property is reflected by the ability of full-length recombinant merlin to form homo-oligomers. Remarkably, the merlin C-ERMAD has a higher affinity for the N-ERMAD of ezrin than the N-ERMAD of merlin. Both the ezrin and merlin N-ERMAD bind EBP50. This interaction with the ezrin N-ERMAD can be inhibited by the presence of the ezrin C-ERMAD, whereas interaction with the merlin N-ERMAD is not inhibited by either C-ERMAD. E3KARP binds tightly to the ezrin N-ERMAD but has little affinity for the merlin N-ERMAD. The implications of these associations and the hierarchies of binding for the function and regulation of merlin and ERM proteins are discussed.
Nguyen
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Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853, USA.
Reczek
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Bretscher
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D015153:Blotting, Western; D002352:Carrier Proteins / Q000737:chemistry* / Q000378:metabolism; D002850:Chromatography, Gel; D003598:Cytoskeletal Proteins / Q000737:chemistry* / Q000378:metabolism; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D008565:Membrane Proteins / Q000737:chemistry* / Q000378:metabolism; D025581:Neurofibromin 2; D010750:Phosphoproteins / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D020033:Protein Isoforms; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D012492:Salts / Q000494:pharmacology; D017923:Sodium-Hydrogen Exchangers; D000099149:Ezrin
D002352:Carrier Proteins; D003598:Cytoskeletal Proteins; D005982:Glutathione Transferase; D008565:Membrane Proteins; D025581:Neurofibromin 2; D010750:Phosphoproteins; D020033:Protein Isoforms; D011993:Recombinant Fusion Proteins; D012492:Salts; D017923:Sodium-Hydrogen Exchangers; D000099149:Ezrin; C093376:sodium-hydrogen exchanger regulatory factor