THE PLASMA MEMBRANE-ACTIN LINKING PROTEIN, EZRIN, IS A GLOMERULAR EPITHELIAL-CELL MARKER IN GLOMERULOGENESIS, IN THE ADULT KIDNEY AND IN GLOMERULAR INJURY

Background. Ezrin belongs to a family of plasma membrane-cytoskeleton linking, actin binding proteins (Ezrin-radixin-Moesin family) involved in signal transduction, growth control, cell-cell adhesion, and micro villi formation. Methods. The expression of ezrin was examined in glom erular cells in culture, during kidney development, in the mature kidn ey, and in five different experimental kidney disease models in the ra t. Results. Ezrin was specifically expressed in glomerular epithelial cells in developing glomeruli in mature glomeruli and in glomerular ep ithelial cells in culture. Distinct from its other family members, moe sin and radixin, which are predominantly expressed in glomerular endot helial and mesangial areas, ezrin protein (by immunohistochemistry) wa s specifically and exclusively modulated during podocyte injury and re generation. Ezrin immunohistochemistry was able to visualize cell body attenuation, pseudocysts, and in particular vacuolation of injured po docytes, a feature that usually has to be identified at the ultrastruc tural level, and was strikingly increased in binucleated podocytes or podocytes that were partially or completely detached from the underlyi ng GEM (frequently also binucleated). Infiltrating macrophages also ex press ezrin, but can easily be differentiated from podocytes by their round shape and higher level of expression. Conclusions. Ezrin likely has a role in the cytoskeletal organization, such as reassembling of a ctin filaments accompanying podocyte injury and regeneration. Since su itable light microscopic markers for the identification of glomerular epithelial cells are rare, ezrin may also be a useful marker for podoc ytes in normal and injured glomeruli.