Identification of a major sialoprotein in the glycocalyx of human visceral glomerular epithelial cells.

Abstract

MethodsGlomerular visceral epithelial cells are endowed with a sialic acid-rich surface coat (the "glomerular epithelial polyanion"), which in rat tissue contains the sialoprotein podocalyxin. We have identified a major membrane sialoprotein in human glomeruli that is similar to rat podocalyxin in its sialic acid-dependent binding of wheat germ agglutinin and in its localization on the surface of glomerular epithelial and endothelial cells, as shown by immunoelectron microscopy, using the monoclonal antibody PHM5. Differences in the sialoproteins of the two species are indicated by the discrepancy of their apparent molecular weights in sodium dodecyl sulfate gels, by the lack of cross reactivity of their specific antibodies, and by the lack of homology of their proteolytic peptide maps. It is therefore possible that the human glomerular sialoprotein and rat podocalyxin are evolutionarily distinct, but have similar functions.

Molecular Cloning and Characterization of Human Podocalyxin-like Protein

“…Kerjaschki and colleagues have described previously a human protein similar to rat podocalyxin which has a size and tissue distribution similar to those of the protein characterized in this report (7). However this molecule recognized by mAb PMH5 differs from rat podocalyxin in apparent molecular mass on SDS-PAGE gels and the sizes of proteolytic fragments seen on peptide digests.…”

“…Sialylation of podocalyxin decreases in the puromycin aminonucleoside model of nephrosis in the rat (6). Efforts to define the podocyte polyanion further have included the description of a major sialoglycoprotein of the human podocyte by Kerjaschki and colleagues (7). Both the lectin binding properties of this protein and its distribution on the surface of podocyte foot processes and the luminal surface of vascular endothelial cells are similar to rat podocalyxin.…”

“…However, this sialoglycoprotein differs from rat podocalyxin in its apparent molecular mass on SDS-PAGE 1 (a 165/170-kDa doublet in contrast to a 140-kDa band for rat podocalyxin) and in its peptide digest pattern. Antibodies to this molecule and those to rat podocalyxin have been reported not to react across species (7), and neither of these molecules has been cloned to date.…”

Identification of Human Embryonic Stem Cell Surface Markers by Combined Membrane-Polysome Translation State Array Analysis and Immunotranscriptional Profiling

“…More importantly, validated cell surface markers for hESCs provide simple tools to enable the separation (and/or removal) of hESCs from mixtures of differentiated cell types. To date, cell surface markers in wide use for the identification of hESCs are mostly antibodies directed against unidentified proteins for which we do not know the encoding gene or antibodies directed against post-translational modifications (Table 1) [1][2][3][4][5][6][7][8][9].…”

Podocalyxin-Targeting Comparative Glycan Profiling Reveals Difference between Human Embryonic Stem Cells and Embryonal Carcinoma Cells

“…Podocalyxin is a member of the CD-34-related family of sialomucins [3][4][5][6][7][8]. Podocalyxin was originally cloned from the human kidney as a component of the podocyte cell glycocalyx, while it was also identified on vascular endothelium and hematopoietic cells [3,4,[9][10][11].…”