A QUANTITATIVE IMMUNOFLUORESCENCE STUDY OF GLOMERULAR CELL-ADHESION PROTEINS IN PROTEINURIC STATES

Whenever there is heavy proteinuria, the glomerular epithelial cells, the podocytes, show dramatic morphological changes which clearly demon strate changes in cell adhesion. However, there is little information on the types of cell adhesion molecules expressed in the normal human glomerulus. Assessments of changes in cell adhesion molecules in human proteinuria have been confined ao semi-quantitative immunostaining fo r integrins, and the results have not been entirely consistent, This s tudy sought first to define which cell adhesion molecules are present in the normal glomerulus, using indirect immunofluorescence and a pane l of antibodies directed against transmembrane adhesion proteins and a gainst several cytoplasmic proteins which are known to be involved in adhesion. A wide variety of integrins were detected, the dominant form being alpha 3 beta 1. The cytoplasmic focal adhesion proteins vinculi n, talin, paxillin, p130CAS, and pp125FAK were detected, although vinc ulin appeared to be confined mainly to the mesangium, The only interce llular adhesion molecule detected in the vicinity of the slit diaphrag m was ZO-1; the results imply that the slit diaphragm does not bear a close relationship to any other form of intercellular junction. Change s in these adhesion components were also studied in proteinuria, using 18 cases each of minimal change nephropathy, 'early' membranous nephr opathy, and normal controls. Fluorescence intensity mas measured by im age capture using a low light video camera and subsequent digital imag e analysis, an approach which demonstrated acceptable reproducibility. The most striking changes were an increase in phosphotyrosine and p13 0CAS ion the nephrotic patients. Contrary to previous reports, little change was found in the expression of the most abundant integrins, nor did overall glomerular staining far ZO-1 alter, These results imply a controlled alteration in glomerular cell adhesion in nephrotic states in man, probable representing increased turnover of cell adhesion str uctures rather than the decrease which has been reported in short-term animal models, This is the first report of increased glomerular phosp hotyrosine in man, which is associated with less stable adhesions and may be related to the loss of foot processes, Using human biopsy mater ial, it was not possible to determine which proteins were phosphorylat ed, but the probable relationships to changes in cytoskeletal structur e and slit diaphragm permeability justify further study. (C) 1997 John Wiley & Sons, Ltd.