Interdomain Interaction of Merlin Isoforms and Its Influence on Intermolecular Binding to NHE-RF*
- From the ‡Molecular Neurogenetics Unit, Massachusetts General Hospital, Charlestown, Massachusetts 02129 and the§Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02215
Abstract
Merlin, the neurofibromatosis 2 tumor suppressor protein, has two major isoforms with alternate C termini and is related to the ERM (ezrin, radixin, moesin) 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.
Footnotes
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↵* This work was supported by National Institutes of Health Grant NS24279 and by funds from Neurofibromatosis Inc. (Massachusetts Chapter).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵¶ To whom correspondence should be addressed: Molecular Neurogenetics Unit, Massachusetts General Hospital, Bldg. 149, 13th St., Charlestown, MA 02129. Tel.: 617-724-9733; Fax: 617-726-5736.E-mail: Ramesh@helix.mgh.harvard.edu.
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↵2 Solomon, F., personal communication.
- Abbreviations:
- NF2
-
neurofibromatosis 2
- NHE-RF
-
regulatory cofactor of Na+-H+ exchanger
- ACE
-
affinity co-electrophoresis
- PIP2
-
phosphatidylinositol 4,5-bisphosphate
- GST
-
glutathione S-transferase
- aa
-
amino acid(s)
- GSH
-
glutathione
- PAGE
-
polyacrylamide gel electrophoresis
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- Received June 18, 1999.
- Revision received August 12, 1999.
- The American Society for Biochemistry and Molecular Biology, Inc.
