Interdomain interaction of merlin isoforms and its influence on intermolecular binding to NHE-RF.
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.
Gonzalez-Agosti
C
C
Molecular Neurogenetics Unit, Massachusetts General Hospital, Charlestown, Massachusetts 02129, USA.
Wiederhold
T
T
Herndon
M E
ME
Gusella
J
J
Ramesh
V
V
D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive / Q000187:drug effects; D019556:COS Cells; D005982:Glutathione Transferase / Q000235:genetics; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008840:Microfilament Proteins / Q000235:genetics / Q000378:metabolism; D025581:Neurofibromin 2; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000494:pharmacology; D018129:Phosphatidylinositol Phosphates / Q000494:pharmacology; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D017923:Sodium-Hydrogen Exchangers
D008565:Membrane Proteins; D008840:Microfilament Proteins; D025581:Neurofibromin 2; D019269:Phosphatidylinositol 4,5-Diphosphate; D018129:Phosphatidylinositol Phosphates; D010750:Phosphoproteins; D020033:Protein Isoforms; D011993:Recombinant Fusion Proteins; D017923:Sodium-Hydrogen Exchangers; C037178:phosphatidylinositol 4-phosphate; C093376:sodium-hydrogen exchanger regulatory factor; C071058:moesin; D005982:Glutathione Transferase