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Updated: Jun 12, 2026
12:19
Single-channel Analysis and Calcium Imaging in the Podocytes of the Freshly Isolated Glomeruli
Published on: June 27, 2015
Beta-cytoplasmic actin localization in vertebrate glomerular podocytes.
Koichiro Ichimura1, Hidetake Kurihara, Tatsuo Sakai
1Department of Anatomy, Juntendo University Graduate School of Medicine, Bunkyo-ku, Tokyo, Japan. ichimura@juntendo.ac.jp
Archives of Histology and Cytology
|June 2, 2010
Summary
Beta-cytoplasmic actin (beta-actin) forms the cytoskeleton in vertebrate podocytes, except in amphibians. Other actin isoforms likely form these structures in amphibians, highlighting evolutionary diversity in cellular architecture.
Area of Science:
- Cell Biology
- Evolutionary Biology
- Biochemistry
Background:
- Glomerular podocyte cytoarchitecture is evolutionarily conserved across vertebrates.
- Actin filaments are essential for maintaining this cytoarchitecture.
- Multiple cytoplasmic actin isoforms exist in vertebrates.
Purpose of the Study:
- To investigate the expression and localization of beta-cytoplasmic actin (beta-actin) in vertebrate podocytes.
- To determine if beta-actin is involved in forming the conserved podocyte cytoarchitecture across species.
Main Methods:
- Immunohistochemical techniques were used to examine beta-actin distribution.
- Six vertebrate species were studied: carp, turtle, quail, rat, newt, and frog.
- Subcellular localization of beta-actin in podocytes was analyzed.
Main Results:
- Beta-actin was found in the foot processes of carp, turtle, quail, and rat podocytes.
- Actin filament condensations were observed in carp and rat podocytes.
- Beta-actin was notably absent in newt and frog podocytes, despite the presence of actin-based foot processes.
Conclusions:
- Beta-actin contributes to the podocyte actin cytoskeleton in most vertebrates studied, excluding amphibians.
- Alternative actin isoforms are likely responsible for actin filament formation in amphibian podocytes.
- This suggests evolutionary divergence in the molecular mechanisms underlying podocyte structure.
Related Concept Videos
01:26Introduction to Actin
Actin is a highly conserved cytoskeletal protein found abundantly in eukaryotic cells. It constitutes 10% weight of the total cellular protein in muscle cells, while in non-muscle cells, it is lower and makes up around 1–5 percent of the total cell protein. Actin found in the unicellular amoebae and complex multicellular animals is around 80% similar, demonstrating their conservation over a billion years of evolution. Actin coding genes are conserved within species and across different species.
01:13Actin Polymerization and Cell Motility
Actin is a family of globular proteins that are highly abundant in eukaryotic cells. It makes up approximately 1-5% of total cell protein concentration. Actin monomers polymerize to form a complex network of polarized filaments, the actin cytoskeleton, that plays a crucial role in many cellular processes, including cell motility, division, endocytosis, and metastasis of cancer cells.
Actin cytoskeleton dynamics can produce pushing, pulling, and resistance forces that help the cell to migrate.
Actin cytoskeleton dynamics can produce pushing, pulling, and resistance forces that help the cell to migrate.
01:42Actin Polymerization
Actin polymerization occurs through the head-to-tail association of binding sites on monomeric actin or G-actin to form filamentous or F-actin. The polymerization can be divided into three phases ̶ nucleation, elongation, and steady-state phase.
The nucleation phase involves forming a stable nucleus consisting of three actin monomers to form a new actin filament. Actin-binding proteins such as formins and Arp2/3 complex help filament growth post-nucleation. The Formins form straight actin...
The nucleation phase involves forming a stable nucleus consisting of three actin monomers to form a new actin filament. Actin-binding proteins such as formins and Arp2/3 complex help filament growth post-nucleation. The Formins form straight actin...
01:11Formation of Higher-order Actin Filaments
The polymerization of G-actin monomers into filamentous F-actin is a multi-step process. Once the F-actins are formed, they can bundle together in different arrangements to form higher-order networks and regulate cellular functions. Common examples include the formation of lamellipodia and filopodia at the cell's leading edge by actin reorganization in a migrating cell. The microvilli on the brush border epithelial cells are also formed through the F-actin network.
The high-order actin networks...
The high-order actin networks...
01:19Actin Filament Depolymerization
Actin filaments (F-actin) are composed of actin subunits. The dissociation of actin monomers can occur from either end of F-actin. The rate of dissociation is faster from the minus-end or the pointed end, where the actin subunits exist with a bound ADP, together known as ADP-actin. The depolymerization of F-actin is aided by proteins, including the actin-depolymerizing factor (ADF) and cofilin family of proteins, gelsolin, and glia maturation factor (GMF).
In F-actin, the ADF/cofilin proteins...
In F-actin, the ADF/cofilin proteins...
01:18Polarity of the Cytoskeleton
The intrinsic polarity of cells can be primarily attributed to two factors- i) the asymmetric accumulation of mobile components such are regulatory molecules and subcellular components across the cell and ii) the orientation of polar cytoskeletal filaments that make up the cytoskeletal networks, specifically microfilaments, and microtubules arranged along the axis of polarity. Interactions between the cytoskeletal filaments are crucial for the establishment and maintenance of the polar nature...