Ezrin oligomers are major cytoskeletal components of placental microvilli: a proposal for their involvement in cortical morphogenesis.

Berryman, Mark; Gary, Ronald K.; Bretscher, Anthony

doi:10.1083/jcb.131.5.1231

Cited by 194 publications

(187 citation statements)

References 64 publications

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“…In contrast, ezrin, a protein that is known to self-associate, demonstrated the presence of oligomers under similar conditions (supplemental Fig. S2B) (33). Together these studies demonstrate the ability of villin to self-associate and further suggest that this property of villin may not be shared by all proteins of its family.…”

Section: Villin Can Bundle Actin Filament Using a Single F-actinmentioning

confidence: 72%

Dimerization and Actin-bundling Properties of Villin and Its Role in the Assembly of Epithelial Cell Brush Borders

George

Wang

Mathew

et al. 2007

Journal of Biological Chemistry

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Villin is a major actin-bundling protein in the brush border of epithelial cells. In this study we demonstrate for the first time that villin can bundle actin filaments using a single F-actin binding site, because it has the ability to self-associate. Using fluorescence resonance energy transfer, we demonstrate villin self-association in living cells in microvilli and in growth factorstimulated cells in membrane ruffles and lamellipodia. Using sucrose density gradient, size-exclusion chromatography, and matrix-assisted laser desorption ionization time-of-flight, the majority of villin was identified as a monomer or dimer. Villin dimers were also identified in Caco-2 cells, which endogenously express villin and Madin-Darby canine kidney cells that ectopically express villin. Using truncation mutants of villin, site-directed mutagenesis, and fluorescence resonance energy transfer, an amino-terminal dimerization site was identified that regulated villin self-association in parallel conformation as well as actin bundling by villin. This detailed analysis describes for the first time microvillus assembly by villin, redefines the actinbundling function of villin, and provides a molecular mechanism for actin bundling by villin, which could have wider implications for other actin cross-linking proteins that share a villin-like headpiece domain. Our study also provides a molecular basis to separate the morphologically distinct actin-severing and actin-bundling properties of villin.

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Section: Villin Can Bundle Actin Filament Using a Single F-actinmentioning

confidence: 72%

Dimerization and Actin-bundling Properties of Villin and Its Role in the Assembly of Epithelial Cell Brush Borders

George

Wang

Mathew

et al. 2007

Journal of Biological Chemistry

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“…4B). Ezrin eluted mainly in two peaks, a higher-MW peak (Ն232,000), most likely containing oligomers (18), and an extended, lower-MW peak Ͼ67,000. Moesin had a similar elution pattern (not shown).…”

Section: Phosphorylated Erm Proteins Form Distinct Complexes With Ebp50mentioning

confidence: 99%

Ezrin–radixin–moesin (ERM)-binding phosphoprotein 50 organizes ERM proteins at the apical membrane of polarized epithelia

Morales

Takahashi

Kreimann

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

203

217

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Ezrin-radixin-moesin (ERM) proteins regulate the organization and function of specific cortical structures in polarized epithelial cells by connecting filamentous (F)-actin to plasma membrane proteins. The contribution of ERM proteins to these structures depends on a conformational change to an active state in which the C-terminal region interacts with F-actin and the N-terminal domain interacts with membrane ligands. The specific ligands necessary for stabilizing ERM proteins at the membrane are not known. By generating mice deficient for ERM-binding phosphoprotein 50͞ Na ؉ /H ؉ exchanger regulatory factor 1 (EBP50͞NHERF1), which binds the N-terminal domain of ERM proteins, we found that EBP50 is required for the maintenance of active ERM proteins at the cortical brush border membranes (BBM) of polarized epithelia. In EBP50(؊͞؊) mice, ERM proteins were significantly decreased specifically in BBM from kidney and small intestine epithelial cells, whereas they remained unchanged in the cytoplasm. In wild-type animals, EBP50 was localized to the BBM compartment where it was processed by cleavage of the ERM-binding motif. In BBM, active ERM proteins formed distinct complexes with full-length EBP50 and with F-actin, suggesting a switch mechanism in which proteolytically processed EBP50 would release ERM proteins to complex with F-actin. The structural defects found in the EBP50(؊͞؊) intestinal microvilli were reminiscent of those described in ezrin(؊͞؊) mice, suggesting a role for EBP50 in organizing apical epithelial membranes. mutant (knockout) mice ͉ brush border membranes ͉ intestine ͉ kidney

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“…The membrane-cytoskeleton linker ezrin is mainly expressed in epithelial cells where it associates to the apical actin-rich structures such as microvilli (Berryman et al, 1993(Berryman et al, , 1995. Recent genetic analyses revealed that ezrin is essential for the morphogenesis of epithelial cells (Fiévet et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

Interaction of Ezrin with the Novel Guanine Nucleotide Exchange Factor PLEKHG6 Promotes RhoG-dependent Apical Cytoskeleton Rearrangements in Epithelial Cells

D'Angelo

Aresta

Blangy

et al. 2007

MBoC

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The mechanisms underlying functional interactions between ERM (ezrin, radixin, moesin) proteins and Rho GTPases are not well understood. Here we characterized the interaction between ezrin and a novel Rho guanine nucleotide exchange factor, PLEKHG6. We show that ezrin recruits PLEKHG6 to the apical pole of epithelial cells where PLEKHG6 induces the formation of microvilli and membrane ruffles. These morphological changes are inhibited by dominant negative forms of RhoG. Indeed, we found that PLEKHG6 activates RhoG and to a much lesser extent Rac1. In addition we show that ezrin forms a complex with PLEKHG6 and RhoG. Furthermore, we detected a ternary complex between ezrin, PLEKHG6, and the RhoG effector ELMO. We demonstrate that PLEKHG6 and ezrin are both required in macropinocytosis. After down-regulation of either PLEKHG6 or ezrin expression, we observed an inhibition of dextran uptake in EGF-stimulated A431 cells. Altogether, our data indicate that ezrin allows the local activation of RhoG at the apical pole of epithelial cells by recruiting upstream and downstream regulators of RhoG and that both PLEKHG6 and ezrin are required for efficient macropinocytosis. INTRODUCTIONThe membrane-cytoskeleton linker ezrin is mainly expressed in epithelial cells where it associates to the apical actin-rich structures such as microvilli (Berryman et al., 1993(Berryman et al., , 1995. Recent genetic analyses revealed that ezrin is essential for the morphogenesis of epithelial cells (Fiévet et al., 2007). In ezrin Ϫ/Ϫ mice, morphological defects in the apical domain of intestinal and retinal pigment epithelial cells have been observed (Saotome et al., 2004;Bonilha et al., 2006). In parietal cells, ezrin knockdown impairs the formation of canalicular apical membrane, resulting in severe achlorhydria (Tamura et al., 2005).How ezrin participates in the assembly of the apical actinrich structures such as microvilli is still poorly understood. The association of ezrin and the highly related proteins radixin and moesin with the cortical actin cytoskeleton is strictly regulated. ERM (ezrin, radixin, moesin) proteins contain a conserved globular N-terminal domain, called the FERM domain (Four point one ezrin, radixin, moesin), involved in the binding to both phosphatidylinositol 4,5 bisphosphate (PIP 2 ; Barret et al., 2000) and plasma membrane proteins and a C-terminal F-actin-binding domain that resides in the last 34 amino acids (Turunen et al., 1994;Bretscher et al., 2002). In the cytoplasm, ERM proteins exist in a closed conformation because of an intramolecular interaction between the N-terminal domain and the last 100 amino acids called N-and C-ERMAD (ERM association domain), respectively . This intramolecular association masks the binding sites for plasma membrane proteins and F-actin. An activation step is required to disrupt this association that occurs through conformational changes induced by sequential binding to PIP 2 and phosphorylation of a conserved C-terminal threonine residue (T567 in ezrin; Matsui et al., 1998;Fié...

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Ezrin oligomers are major cytoskeletal components of placental microvilli: a proposal for their involvement in cortical morphogenesis.

Cited by 194 publications

References 64 publications

Dimerization and Actin-bundling Properties of Villin and Its Role in the Assembly of Epithelial Cell Brush Borders

Dimerization and Actin-bundling Properties of Villin and Its Role in the Assembly of Epithelial Cell Brush Borders

Ezrin–radixin–moesin (ERM)-binding phosphoprotein 50 organizes ERM proteins at the apical membrane of polarized epithelia

Interaction of Ezrin with the Novel Guanine Nucleotide Exchange Factor PLEKHG6 Promotes RhoG-dependent Apical Cytoskeleton Rearrangements in Epithelial Cells

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