Hsp27 regulates podocyte cytoskeletal changes in an in vitro model of podocyte process retraction.

Nephrotic syndrome (NS) is characterized by structural changes in the actin-rich foot processes of glomerular podocytes. We previously identified high concentrations of the small heat shock protein hsp27 within podocytes as well as increased glomerular accumulation and phosphorylation of hsp27 in puromycin aminonucleoside (PAN) -induced experimental NS. Here we analyzed murine podocytes stably transfected with hsp27 sense, antisense, and vector control constructs using a newly developed in vitro PAN model system. Cell morphology and the microfilament structure of untreated sense and antisense transfectants were altered compared with controls. Vector cell survival, polymerized actin content, cell area, and hsp27 content increased after 1.25 microg/ml PAN treatment and decreased after 5.0 microg/ml treatment. In contrast, sense cells were unaffected by 1.25 microg/ml PAN treatment whereas antisense cells showed decreases or no changes in all parameters. Treatment of sense cells with 5.0 microg/ml PAN resulted in increased cell survival and cell area whereas antisense cells underwent significant decreases in all parameters. Hsp27 provided dramatic protection against PAN-induced microfilament disruption in sense > vector > antisense cells. We conclude that hsp27 is able to regulate both the morphological and actin cytoskeletal response of podocytes in an in vitro model of podocyte injury.