FIGURE 1.

sdk-1 is overexpressed in podocytes in FSGS. A, expression of sdk-1 RNA is significantly up-regulated in podocytes in cell culture when exposed to either HIV-1 infection or PAN as determined by quantitative PCR. Massive up-regulation of sdk-1 RNA after HIV-1 infection was previously reported (16, 17). WT, wild type. Error bars indicate S.E. B, the up-regulation of sdk-1 protein after exposure to PAN was confirmed by Western blotting. C, 293T cells transfected with an sdk-1 expression construct were used as the positive control. C, sdk-1 protein expression was detected by immunofluorescence in podocytes in PAN-treated rats but not in sham-injected controls. Podocyte-specific expression was confirmed by colocalization with the podocyte-specific marker vimentin. D, upper, a novel rabbit anti-human sdk-1 antibody specifically interacts with lysate from cells transfected with an sdk-1, but not an sdk-2, expression plasmid. Lower, when preincubated with excess immunizing peptide, this antibody showed no reactivity against human specimens. GAPDH, glyceraldehyde-3-phosphate dehydrogenase. E, by immunohistochemistry, sdk-1 protein was detected in a podocyte distribution in kidney biopsies from two patients with idiopathic FSGS but not in normal human kidney.