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Reversible phosphorylation of ezrin T567: conformation, activity and physiology
Author(s) -
Zhu Lixin,
Zhou Rihong,
Mettler Shelley,
Wu Tim,
Abbas Aennes,
Forte John G
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.6.a913-d
Subject(s) - ezrin , phosphorylation , chemistry , microbiology and biotechnology , dephosphorylation , biophysics , actin , mutant , phosphatase , radixin , secretion , cytoskeleton , biochemistry , biology , cell , gene
In its dormant state the membrane cytoskeletal linker protein ezrin takes on intramolecular N‐C binding conformation. Many studies indicate that phosphorylation of T567 activates ezrin by eliminating N‐C binding. However, in gastric parietal cells expressed T567D mutant ezrin was mis‐localized and caused a negative effect on acid secretion (J Cell Sci, 118:, 2005). Ezrin is normally located on apical membrane and positively associated with acid secretion. The situation is even more complicated by our finding that ezrin T567 phosphorylation is increased when parietal cells are stimulated to secrete acid. The apparent inconsistency inspired an hypothesis that ezrin activity is regulated by continuous phosphorylation/dephosphorylation on T567. To test this, phosphatase inhibitors increased T567 phosphorylation, consistent with high T567‐phosphate turnover. T567A and T567D mutants, made on a YFP‐ezrin‐CFP construct to probe N‐C binding by FRET, revealed N‐ and C‐termini are more separated in TD than WT or TA, thus T567 phosphorylation opens N‐C interaction. Importantly, the conformational change leads to enhanced ezrin activity: more TD mutant co‐sedimented with F‐actin and binds more tightly to membrane than WT or TA. Finally, FRAP (fluorescence recovery after photobleach) indicates that TD mutant has longer recovery time than WT or TA, indicating the T567D form of ezrin is tightly associated with F‐actin and membrane, restricting normal membrane activity. These data emphasize the importance of reversible phosphorylation of ezrin and give one explanation why T567D was trapped in basolateral membrane.