The Glomerular Slit Diaphragm Is a Modified Adherens Junction

. The glomerular slit diaphragm between podocyte foot processes shares typical morphologic features with an adherens junction. Differentiated cultured podocytes form cellular structures comparable to filtration slits in vivo . At those sites, zonula occludens-1 (ZO-1) was coexpressed with P-cadherin as well as with α-, β-, and γ-catenin. In situ , P-cadherin was detected at the slit diaphragm in association with ZO-1 as shown by confocal microscopy and immunogold double labeling electron microscopy. P-cadherin expression in vivo and in vitro was confirmed by reverse transcription-PCR. These findings led to the concept that the slit diaphragm represents an adherens junction composed of P-cadherin, α-, β-, and γ-catenin, and ZO-1. In contrast to an adherens junction of a similar composition recently described in cultured fibroblasts, the slit diaphragm complex does not contain vinculin, which was found in nearby focal contacts. A P-cadherinbased adherens junction is well-suited to explain the zipper-like structure of the slit diaphragm. The present study should allow new avenues leading to the identification of additional slit diaphragm-associated proteins conferring specificity to this unique cell junction.