Abstract
Podocytes are an integral part of the glomerular filtration barrier, a structure that prevents filtration of large proteins and macromolecules into the urine. Podocyte function is dependent on actin cytoskeleton regulation within the foot processes, structures that link podocytes to the glomerular basement membrane. Actin cytoskeleton dynamics in podocyte foot processes are complex and regulated by multiple proteins and other factors. There are two key signal integration and structural hubs within foot processes that regulate the actin cytoskeleton: the slit diaphragm and focal adhesions. Both modulate actin filament extension as well as foot process mobility. No matter what the initial cause, the final common pathway of podocyte damage is dysregulation of the actin cytoskeleton leading to foot process retraction and proteinuria. Disruption of the actin cytoskeleton can be due to acquired causes or to genetic mutations in key actin regulatory and signaling proteins. Here, we describe the major structural and signaling components that regulate the actin cytoskeleton in podocytes as well as acquired and genetic causes of actin dysregulation.
Highlights
Proteinuria is one of the hallmarks of kidney disease
Leakage of serum proteins into the urine is prevented by the glomerular filtration barrier (GFB), a structure consisting of fenestrated endothelial cells, the glomerular basement membrane (GBM) and podocytes
In the second and final stage of Foot process effacement (FPE), the foot processes retract into primary podocyte processes which results in the cell body adhering to the GBM
Summary
Proteinuria is one of the hallmarks of kidney disease. Under normal circumstances, less than 150 mg a day of protein is found in the urine. Dynamics motility and intracellular transport [3] To carry out these functions, actin filaments are arranged in a Changes in the actin cytoskeleton within a cell are necessary for maintenance of cell shape, variety of ways. Filaments are cell motility and intracellular transport [3] To carry out these functions, actin filaments are arranged in extended by nucleation, or the formation of actin dimers and trimers, which is the rate limiting step a variety of ways. At the front of the cell, actin filaments are arranged into branched and dynamic and elongates rapidly and a pointed end which elongates at a rate ten-fold slower than that of cross-linked structures known as lamellipodia. Actin polymerization into filaments is tightly controlled by actin-binding proteins [7]
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