Limits...
Actin cross-linking protein palladin and spermatogenesis.

Qian X, Mruk DD, Cheng YH, Cheng CY - Spermatogenesis (2013)

Bottom Line: Herein, we summarize some of the latest findings in the field regarding a novel actin cross-linker and actin-bundling protein called palladin.We also discuss in this opinion article the likely role of palladin in regulating actin filament bundles at the ES during spermatogenesis, highlighting the significant of palladin and how this protein is plausibly working in concert with other actin-binding/regulatory proteins and components of polarity proteins to regulate the cyclic events of actin organization and re-organization during the epithelial cycle of spermatogenesis.We also propose a hypothetic model by which palladin regulates ES restructuring during the epithelial cycle of spermatogenesis.

View Article: PubMed Central - PubMed

Affiliation: The Mary M. Wohlford Laboratory for Male Contraceptive Research; Center for Biomedical Research; Population Council; New York, NY USA ; School of Basic Medicine; Peking Union Medical College; Beijing, China.

ABSTRACT
In the seminiferous epithelium of the mammalian testis, the most distinctive ultrastructure is the extensive bundles of actin filaments that lie near the Sertoli-spermatid interface and the Sertoli-Sertoli cell interface known as the apical ectoplasmic specialization (apical ES) and the basal ES, respectively. These actin filament bundles not only confer strong adhesion at these sites, they are uniquely found in the testis. Recent studies have shown that ES also confers spermatid and Sertoli cell polarity in the seminiferous epithelium during the epithelial cycle. While these junctions were first described in the 1970s, there are few functional studies in the literature to examine the regulation of these actin filament bundles. It is conceivable that these actin filament bundles at the ES undergo extensive re-organization to accommodate changes in location of developing spermatids during spermiogenesis as spermatids are transported across the seminiferous epithelium. Additionally, these actin filaments are rapidly reorganized during BTB restructuring to accommodate the transit of preleptotene spermatocytes across the barrier at stage VIII of the epithelial cycle. Thus, actin binding and regulatory proteins are likely involved in these events to confer changes in F-actin organization at these sites. Interestingly, there are no reports in the field to study these regulatory proteins until recently. Herein, we summarize some of the latest findings in the field regarding a novel actin cross-linker and actin-bundling protein called palladin. We also discuss in this opinion article the likely role of palladin in regulating actin filament bundles at the ES during spermatogenesis, highlighting the significant of palladin and how this protein is plausibly working in concert with other actin-binding/regulatory proteins and components of polarity proteins to regulate the cyclic events of actin organization and re-organization during the epithelial cycle of spermatogenesis. We also propose a hypothetic model by which palladin regulates ES restructuring during the epithelial cycle of spermatogenesis.

No MeSH data available.


Related in: MedlinePlus

Figure 1. A schematic drawing illustrating the functional domains of a 90 kDa isoform of palladin polypeptide. In the testis, the predominant form of palladin detected by immunoblotting is the 90 kDa isoform, which is composed of a protein-rich region (PR region) for protein-protein interactions near its N terminus, and three IgC2 domains close to its C terminus for binding to F-actin to confer its F-actin cross-linking and F-actin bundling activity.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3644046&req=5

Figure 1: Figure 1. A schematic drawing illustrating the functional domains of a 90 kDa isoform of palladin polypeptide. In the testis, the predominant form of palladin detected by immunoblotting is the 90 kDa isoform, which is composed of a protein-rich region (PR region) for protein-protein interactions near its N terminus, and three IgC2 domains close to its C terminus for binding to F-actin to confer its F-actin cross-linking and F-actin bundling activity.

Mentions: Palladin (Fig. 1), myotilin and myopalladin form a unique family of actin-binding proteins that were known to have a scaffolding function.1,2 Palladin was initially found to co-localize with α-actinin in stress fibers in cells, focal adhesions (also known as focal contacts) and cell-cell junctions,3 and also associated with α-actinin to organize actin-containing microfilaments in smooth muscle and nonmuscle cells,4 serving a scaffolding role in cytoskeleton. Unlike palladin, which is found in virtually all mammalian tissues and cells and localized to actin-based structures (e.g., stress fibers, focal adhesions),1,2,5,6 myopalladin is restricted to the heart and skeletal muscle,7 whereas myotilin is mostly expressed in skeletal muscle.8 Subsequent studies have shown that palladin, besides serving as a cytoskeletal scaffold, also binds tightly to Eps8 (epidermal growth factor receptor pathway substrate 8, an actin-barbed end capping and bundling protein), and it is also an actin cross-linker that binds to F-actin using its Ig-like (immunoglobulin-like) domains.9 Due to this unusual actin cross-linking activity and the fact that it is tightly associated with Eps8, it is becoming increasingly clear that palladin is a crucial molecule that confers and regulates actin filament bundles in mammalian cells, such as those found in the ectoplasmic specialization (ES) in the seminiferous epithelium of the mammalian testis.


Actin cross-linking protein palladin and spermatogenesis.

Qian X, Mruk DD, Cheng YH, Cheng CY - Spermatogenesis (2013)

Figure 1. A schematic drawing illustrating the functional domains of a 90 kDa isoform of palladin polypeptide. In the testis, the predominant form of palladin detected by immunoblotting is the 90 kDa isoform, which is composed of a protein-rich region (PR region) for protein-protein interactions near its N terminus, and three IgC2 domains close to its C terminus for binding to F-actin to confer its F-actin cross-linking and F-actin bundling activity.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3644046&req=5

Figure 1: Figure 1. A schematic drawing illustrating the functional domains of a 90 kDa isoform of palladin polypeptide. In the testis, the predominant form of palladin detected by immunoblotting is the 90 kDa isoform, which is composed of a protein-rich region (PR region) for protein-protein interactions near its N terminus, and three IgC2 domains close to its C terminus for binding to F-actin to confer its F-actin cross-linking and F-actin bundling activity.
Mentions: Palladin (Fig. 1), myotilin and myopalladin form a unique family of actin-binding proteins that were known to have a scaffolding function.1,2 Palladin was initially found to co-localize with α-actinin in stress fibers in cells, focal adhesions (also known as focal contacts) and cell-cell junctions,3 and also associated with α-actinin to organize actin-containing microfilaments in smooth muscle and nonmuscle cells,4 serving a scaffolding role in cytoskeleton. Unlike palladin, which is found in virtually all mammalian tissues and cells and localized to actin-based structures (e.g., stress fibers, focal adhesions),1,2,5,6 myopalladin is restricted to the heart and skeletal muscle,7 whereas myotilin is mostly expressed in skeletal muscle.8 Subsequent studies have shown that palladin, besides serving as a cytoskeletal scaffold, also binds tightly to Eps8 (epidermal growth factor receptor pathway substrate 8, an actin-barbed end capping and bundling protein), and it is also an actin cross-linker that binds to F-actin using its Ig-like (immunoglobulin-like) domains.9 Due to this unusual actin cross-linking activity and the fact that it is tightly associated with Eps8, it is becoming increasingly clear that palladin is a crucial molecule that confers and regulates actin filament bundles in mammalian cells, such as those found in the ectoplasmic specialization (ES) in the seminiferous epithelium of the mammalian testis.

Bottom Line: Herein, we summarize some of the latest findings in the field regarding a novel actin cross-linker and actin-bundling protein called palladin.We also discuss in this opinion article the likely role of palladin in regulating actin filament bundles at the ES during spermatogenesis, highlighting the significant of palladin and how this protein is plausibly working in concert with other actin-binding/regulatory proteins and components of polarity proteins to regulate the cyclic events of actin organization and re-organization during the epithelial cycle of spermatogenesis.We also propose a hypothetic model by which palladin regulates ES restructuring during the epithelial cycle of spermatogenesis.

View Article: PubMed Central - PubMed

Affiliation: The Mary M. Wohlford Laboratory for Male Contraceptive Research; Center for Biomedical Research; Population Council; New York, NY USA ; School of Basic Medicine; Peking Union Medical College; Beijing, China.

ABSTRACT
In the seminiferous epithelium of the mammalian testis, the most distinctive ultrastructure is the extensive bundles of actin filaments that lie near the Sertoli-spermatid interface and the Sertoli-Sertoli cell interface known as the apical ectoplasmic specialization (apical ES) and the basal ES, respectively. These actin filament bundles not only confer strong adhesion at these sites, they are uniquely found in the testis. Recent studies have shown that ES also confers spermatid and Sertoli cell polarity in the seminiferous epithelium during the epithelial cycle. While these junctions were first described in the 1970s, there are few functional studies in the literature to examine the regulation of these actin filament bundles. It is conceivable that these actin filament bundles at the ES undergo extensive re-organization to accommodate changes in location of developing spermatids during spermiogenesis as spermatids are transported across the seminiferous epithelium. Additionally, these actin filaments are rapidly reorganized during BTB restructuring to accommodate the transit of preleptotene spermatocytes across the barrier at stage VIII of the epithelial cycle. Thus, actin binding and regulatory proteins are likely involved in these events to confer changes in F-actin organization at these sites. Interestingly, there are no reports in the field to study these regulatory proteins until recently. Herein, we summarize some of the latest findings in the field regarding a novel actin cross-linker and actin-bundling protein called palladin. We also discuss in this opinion article the likely role of palladin in regulating actin filament bundles at the ES during spermatogenesis, highlighting the significant of palladin and how this protein is plausibly working in concert with other actin-binding/regulatory proteins and components of polarity proteins to regulate the cyclic events of actin organization and re-organization during the epithelial cycle of spermatogenesis. We also propose a hypothetic model by which palladin regulates ES restructuring during the epithelial cycle of spermatogenesis.

No MeSH data available.


Related in: MedlinePlus