[Molecular pathology of the glomerular sialoglycoprotein podocalyxin, a major component of the glomerular polyanion in experimental and human minimal glomerular change].

Visceral glomerular epithelial cells (or podocytes) are endowed with a highly polyanionic glycokalyx which is rich in sialic acid. We have identified a single sialoprotein - MW 140 kD - which we have called "Podocalyxin", and which is the major carrier of glomerular sialic acid. We have shown that podocalyxin of normal rat glomeruli contains 20 sialic acid residues per molecule, whereas in aminonucleoside nephrotic glomeruli only 4-5 sialic acid per molecule are present. We conclude that the loss of histochemical staining for the "glomerular polyanion" is due both to the reduction of sialic acid per podocalyxin molecule, and to the reduction of the surface of the podocyte's plasmalemma caused by spreading of footprocesses. We furtheron report that also in human glomeruli there is a sialoprotein which is distinct from rat podocalyxin in its electrophoretic mobility and immunological structure, but otherwise shows all features which are characteristic for rat podocalyxin.