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Ezrin: a regulator of actin microfilaments in cell junctions of the rat testis.

Gungor-Ordueri NE, Celik-Ozenci C, Cheng CY - Asian J. Androl. (2015 Jul-Aug)

Bottom Line: Thus, these proteins are crucial to confer integrity of the apical membrane domain and its associated junctional complex, namely the tight junction and the adherens junction.Since ectoplasmic specialization (ES) is an F-actin-rich testis-specific anchoring junction-a highly dynamic ultrastructure in the seminiferous epithelium due to continuous transport of germ cells, in particular spermatids, across the epithelium during the epithelial cycle-it is conceivable that ERM proteins are playing an active role in these events.Although these proteins were first reported almost 25 years and have since been extensively studied in multiple epithelia/endothelia, few reports are found in the literature to examine their role in the actin filament bundles at the ES.

View Article: PubMed Central - PubMed

Affiliation: The Mary M. Wohlford Laboratory for Male Contraceptive Research, Center for Biomedical Research, Population Council, New York, USA.

ABSTRACT
Ezrin, radixin, moesin and merlin (ERM) proteins are highly homologous actin-binding proteins that share extensive sequence similarity with each other. These proteins tether integral membrane proteins and their cytoplasmic peripheral proteins (e.g., adaptors, nonreceptor protein kinases and phosphatases) to the microfilaments of actin-based cytoskeleton. Thus, these proteins are crucial to confer integrity of the apical membrane domain and its associated junctional complex, namely the tight junction and the adherens junction. Since ectoplasmic specialization (ES) is an F-actin-rich testis-specific anchoring junction-a highly dynamic ultrastructure in the seminiferous epithelium due to continuous transport of germ cells, in particular spermatids, across the epithelium during the epithelial cycle-it is conceivable that ERM proteins are playing an active role in these events. Although these proteins were first reported almost 25 years and have since been extensively studied in multiple epithelia/endothelia, few reports are found in the literature to examine their role in the actin filament bundles at the ES. Studies have shown that ezrin is also a constituent protein of the actin-based tunneling nanotubes (TNT) also known as intercellular bridges, which are transient cytoplasmic tubular ultrastructures that transport signals, molecules and even organelles between adjacent and distant cells in an epithelium to coordinate cell events that occur across an epithelium. Herein, we critically evaluate recent data on ERM in light of recent findings in the field in particular ezrin regarding its role in actin dynamics at the ES in the testis, illustrating additional studies are warranted to examine its physiological significance in spermatogenesis.

No MeSH data available.


Related in: MedlinePlus

A schematic drawing to illustrate the functional domains of members of the ezrin, radixin, moesin and merlin (ERM-Merlin) family proteins. All members of the ERM protein family share common structural features of band 4.1 (band 4.1 was designated by Coomassie blue-stained polyacrylamide gel following SDS-PAGE using extracts of erythrocyte plasma membrane7), the presence of a band 4.1/ERM domain, an α-helical domain, a proline-rich domain, and an F-actin-binding region in the C-terminal region. ERM-Merlin proteins are activated by phosphorylation at the corresponding Thr or Ser residue.
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Figure 1: A schematic drawing to illustrate the functional domains of members of the ezrin, radixin, moesin and merlin (ERM-Merlin) family proteins. All members of the ERM protein family share common structural features of band 4.1 (band 4.1 was designated by Coomassie blue-stained polyacrylamide gel following SDS-PAGE using extracts of erythrocyte plasma membrane7), the presence of a band 4.1/ERM domain, an α-helical domain, a proline-rich domain, and an F-actin-binding region in the C-terminal region. ERM-Merlin proteins are activated by phosphorylation at the corresponding Thr or Ser residue.

Mentions: Ezrin, radixin, moesin (ERM) together with merlin (moesin/ezrin/radixin-like protein, a tumor suppressor, also known as schwannomin or neurofibromin 2) belong to a family of structural proteins called ERM-merlin that cross-link actin filaments of the actin-based cytoskeleton to the plasma membrane, they also create a scaffold for signaling molecules that are involved in the regulation of cell proliferation, migration, and survival.12345 Studies have shown that ERMs are also involved in tumorigenesis6 due to their involvement in tumor cell migration, such as metastasis. Ezrin is the protein originally identified as band 4.1 detected on Coomassie blue-stained gels when first extracted from erythrocyte plasma membrane.7 Subsequent studies have shown that all ERM proteins share a conserved domain known as band 4.1/ERM (FERM) domain, which is also found in several cytoskeletal-associated proteins, such as focal adhesion kinase (FAK), myosins (e.g., myosin VIIa, X, XV), talins, guanine-nucleotide-exchange factors (GEFs)89 (Figure 1). These proteins (e.g., FAK, talin, GEF and myosin) thus interact with ERM-merlin proteins via their FERM domains. While ERM-merlin proteins are highly homologous proteins and ERMs have similar binding partners (Figure 1) as well as subcellular localization in the mammalian body, however, ERM display different tissue-specific expression patterns: ezrin is expressed mostly in polarized epithelial and mesothelial cells,1011 radaxin in hepatocytes,1213 moesin primarily in endothelial and lymphoid cells,1014 and merlin in nervous tissue.1516 These proteins are also concentrated abundantly to the undercoat of the plasma membrane of microvilli in the corresponding cells and/or tissues. Thus, ezrin is also known as cytovillin or villin-2. In short, ERM proteins tether integral membrane and cytoplasmic proteins (e.g., adaptors, nonreceptor protein kinases, phosphatases) to actin filaments of the actin-based cytoskeleton, and they also organize apical membrane domain, including tight junction (TJ) and the underlying adherens junction (AJs) of the junctional complex in both epithelia and endothelia.


Ezrin: a regulator of actin microfilaments in cell junctions of the rat testis.

Gungor-Ordueri NE, Celik-Ozenci C, Cheng CY - Asian J. Androl. (2015 Jul-Aug)

A schematic drawing to illustrate the functional domains of members of the ezrin, radixin, moesin and merlin (ERM-Merlin) family proteins. All members of the ERM protein family share common structural features of band 4.1 (band 4.1 was designated by Coomassie blue-stained polyacrylamide gel following SDS-PAGE using extracts of erythrocyte plasma membrane7), the presence of a band 4.1/ERM domain, an α-helical domain, a proline-rich domain, and an F-actin-binding region in the C-terminal region. ERM-Merlin proteins are activated by phosphorylation at the corresponding Thr or Ser residue.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4492059&req=5

Figure 1: A schematic drawing to illustrate the functional domains of members of the ezrin, radixin, moesin and merlin (ERM-Merlin) family proteins. All members of the ERM protein family share common structural features of band 4.1 (band 4.1 was designated by Coomassie blue-stained polyacrylamide gel following SDS-PAGE using extracts of erythrocyte plasma membrane7), the presence of a band 4.1/ERM domain, an α-helical domain, a proline-rich domain, and an F-actin-binding region in the C-terminal region. ERM-Merlin proteins are activated by phosphorylation at the corresponding Thr or Ser residue.
Mentions: Ezrin, radixin, moesin (ERM) together with merlin (moesin/ezrin/radixin-like protein, a tumor suppressor, also known as schwannomin or neurofibromin 2) belong to a family of structural proteins called ERM-merlin that cross-link actin filaments of the actin-based cytoskeleton to the plasma membrane, they also create a scaffold for signaling molecules that are involved in the regulation of cell proliferation, migration, and survival.12345 Studies have shown that ERMs are also involved in tumorigenesis6 due to their involvement in tumor cell migration, such as metastasis. Ezrin is the protein originally identified as band 4.1 detected on Coomassie blue-stained gels when first extracted from erythrocyte plasma membrane.7 Subsequent studies have shown that all ERM proteins share a conserved domain known as band 4.1/ERM (FERM) domain, which is also found in several cytoskeletal-associated proteins, such as focal adhesion kinase (FAK), myosins (e.g., myosin VIIa, X, XV), talins, guanine-nucleotide-exchange factors (GEFs)89 (Figure 1). These proteins (e.g., FAK, talin, GEF and myosin) thus interact with ERM-merlin proteins via their FERM domains. While ERM-merlin proteins are highly homologous proteins and ERMs have similar binding partners (Figure 1) as well as subcellular localization in the mammalian body, however, ERM display different tissue-specific expression patterns: ezrin is expressed mostly in polarized epithelial and mesothelial cells,1011 radaxin in hepatocytes,1213 moesin primarily in endothelial and lymphoid cells,1014 and merlin in nervous tissue.1516 These proteins are also concentrated abundantly to the undercoat of the plasma membrane of microvilli in the corresponding cells and/or tissues. Thus, ezrin is also known as cytovillin or villin-2. In short, ERM proteins tether integral membrane and cytoplasmic proteins (e.g., adaptors, nonreceptor protein kinases, phosphatases) to actin filaments of the actin-based cytoskeleton, and they also organize apical membrane domain, including tight junction (TJ) and the underlying adherens junction (AJs) of the junctional complex in both epithelia and endothelia.

Bottom Line: Thus, these proteins are crucial to confer integrity of the apical membrane domain and its associated junctional complex, namely the tight junction and the adherens junction.Since ectoplasmic specialization (ES) is an F-actin-rich testis-specific anchoring junction-a highly dynamic ultrastructure in the seminiferous epithelium due to continuous transport of germ cells, in particular spermatids, across the epithelium during the epithelial cycle-it is conceivable that ERM proteins are playing an active role in these events.Although these proteins were first reported almost 25 years and have since been extensively studied in multiple epithelia/endothelia, few reports are found in the literature to examine their role in the actin filament bundles at the ES.

View Article: PubMed Central - PubMed

Affiliation: The Mary M. Wohlford Laboratory for Male Contraceptive Research, Center for Biomedical Research, Population Council, New York, USA.

ABSTRACT
Ezrin, radixin, moesin and merlin (ERM) proteins are highly homologous actin-binding proteins that share extensive sequence similarity with each other. These proteins tether integral membrane proteins and their cytoplasmic peripheral proteins (e.g., adaptors, nonreceptor protein kinases and phosphatases) to the microfilaments of actin-based cytoskeleton. Thus, these proteins are crucial to confer integrity of the apical membrane domain and its associated junctional complex, namely the tight junction and the adherens junction. Since ectoplasmic specialization (ES) is an F-actin-rich testis-specific anchoring junction-a highly dynamic ultrastructure in the seminiferous epithelium due to continuous transport of germ cells, in particular spermatids, across the epithelium during the epithelial cycle-it is conceivable that ERM proteins are playing an active role in these events. Although these proteins were first reported almost 25 years and have since been extensively studied in multiple epithelia/endothelia, few reports are found in the literature to examine their role in the actin filament bundles at the ES. Studies have shown that ezrin is also a constituent protein of the actin-based tunneling nanotubes (TNT) also known as intercellular bridges, which are transient cytoplasmic tubular ultrastructures that transport signals, molecules and even organelles between adjacent and distant cells in an epithelium to coordinate cell events that occur across an epithelium. Herein, we critically evaluate recent data on ERM in light of recent findings in the field in particular ezrin regarding its role in actin dynamics at the ES in the testis, illustrating additional studies are warranted to examine its physiological significance in spermatogenesis.

No MeSH data available.


Related in: MedlinePlus