| Research Abstract |
During a search for cadherin-related molecules expressed in rat glomeruli by PT-PCR with degenerate primers, we have isolated cDNA encoding FAT and protocadherin (PCDH) 68.
FAT, a member of the cadherin super family, is a large transmembrane protein. To localize FAT and to speculate its role in the kidney, we examined its expression in-the rat kidney in the physiological condition and PAN nephrosis by using ribonuclease protection assay (RPA), Western blotting (WB) and immunoelectron microscopy (IEM). By IEM, it was demonstrated that FAT is a component of slit diaphragms. In PAN nephrosis, increase in FAT expression in glomeruli was shown by RPA, WB, and immunostaining. IEM showed that FAT is localized in the tight junction-type intercellular junction of podocytes in addition to slit diaphragms. The above findings suggest that FAT is one of basic constituents of intercellularjunctions of podocytes.
PCDH68 also belongs to the cadherin superfamily. Its sequence was different in the cytoplasmic domain from that of human PCDH68 that has been registered. From the sequence of our cloned human PCDH68 and the result of Northern blot in the rat, it is unlikely that there are isotypes of PCDH68. RPA revealed its distinct expression in glomeruli in the kidney, cerebrum, cerebellum, lung and spleen. Anti-Thy-1 antibody treatment did not reduce its glomerular expression, indicating that mesangial cells do not express PCDH68. In PAN nephrosis, the level of the expression in glomeruli did not change. Now, we have hypothesized that PCDH68 exists in the tight junction-type intercellular junction of podocytes. To clarify the precise localization of PCDH68, we are preparing the antibody against PCDH68 cytoplasmic domain.
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