Newly identified cytoskeletal components are associated with dynamic changes of podocyte foot processes

Proteinuria, one of the main manifestations of nephrotic syndrome, is an important risk factor for the progression of renal diseases. Podocyte foot processes (FPs) injury induces proteinuria in most renal diseases. The podocyte cytoskeleton plays important roles in maintaining the normal morphology of FPs. However, the underlying cytoskeletal component that initiates and regulates the dynamic changes of FPs is still unclear. Here, the involved podocyte cytoskeletal molecules were explored on different days in puromycin aminonucleoside nephropathy rats.

Microarray analysis of isolated glomeruli was performed at Day 2, Day 10 and Day 15 in puromycin aminonucleoside nephropathy rats. Cytoskeletal genebank was established by sorting with the keyword 'cytoskeleton' from PUBMED genebank to identify the differential cytoskeleton genes. Microarray results were further confirmed by real-time PCR, western blot and double immunolabelling to validate their localizations.

Nine different cytoskeletal genes were found to be involved in the dynamic changes of FPs in puromycin aminonucleoside nephropathy rats, including six up-regulated (Tagln, Actr2, Dnm3, Arc, Vcl and Birc5) and three down-regulated (Krt2-7, Nebl and Tnnc1). The differential expression of transgelin, survivin, arp2, cytokeratin7 and vinculin was verified by real-time PCR and western blot. Double immunolabelling revealed that five cytoskeletal proteins indeed colocalized with podocyte specific markers synaptopodin or alpha-actinin-4. In addition, similar expression and distribution changes were detected in patients with proteinuric renal diseases and puromycin aminonucleoside-treated podocytes.

We identified five novel podocyte cytoskeletal proteins and found that they were associated with the dynamic changes of FPs in podocyte injury.