Interdomain Interaction of Merlin Isoforms and Its Influence on Intermolecular Binding to NHE-RF

• Published in: The Journal of biological chemistry 1999-11, Vol.274 (48), p.34438-34442
• Main Authors: Gonzalez-Agosti, C, Wiederhold, T, Herndon, M E, Gusella, J, Ramesh, V
• Format: Article
• Language: English
• Subjects: Animals; Binding Sites; Binding, Competitive - drug effects; COS Cells; Glutathione Transferase - genetics; Membrane Proteins - chemistry; Membrane Proteins - genetics; Membrane Proteins - metabolism; Microfilament Proteins - genetics; Microfilament Proteins - metabolism; Neurofibromin 2; Phosphatidylinositol 4,5-Diphosphate - pharmacology; Phosphatidylinositol Phosphates - pharmacology; Phosphoproteins - genetics; Phosphoproteins - metabolism; Protein Binding; Protein Isoforms - genetics; Protein Isoforms - metabolism; Protein Structure, Tertiary; Recombinant Fusion Proteins - genetics; Recombinant Fusion Proteins - metabolism; Sodium-Hydrogen Exchangers
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.274.48.34438

Merlin, the neurofibromatosis 2 tumor suppressor protein, has two major isoforms with alternate C termini and is related to the ERM ( e zrin, r adixin, m oesin) proteins. Regulation of the ERMs involves intramolecular and/or intermolecular head-to-tail associations between family members. We have determined whether merlin undergoes similar interactions, and our findings indicate that the C terminus of merlin isoform 1 is able to associate with its N-terminal domain in a head-to-tail fashion. However, the C terminus of isoform 2 lacks this property. Similarly, the N terminus of merlin can also associate with C terminus of moesin. We have also explored the effect of merlin self-association on binding to the regulatory cofactor of Na + -H + exchanger (NHE-RF), an interacting protein for merlin and the ERMs. Merlin isoform 2 captures more NHE-RF than merlin isoform 1 in affinity binding assays, suggesting that in full-length merlin isoform 1, the NHE-RF binding site is masked because of the self-interactions of merlin. Treatment with a phospholipid known to decrease self-association of ERMs enhances the binding of merlin isoform 1 to NHE-RF. Thus, although isoform 1 resembles the ERM proteins, which transition between inactive (closed) and active (open) states, isoform 2 is distinct, existing only in the active (open) state and presumably constitutively more available for interaction with other protein partners.