ABSTRACT
The urothelium, a distinct epithelial tissue lining the urinary tract, serves as an essential component in preserving urinary tract integrity and thwarting infections. The asymmetric unit membrane (AUM), primarily composed of the uroplakin complex, constitutes a critical permeability barrier in fulfilling this role. However, the molecular architectures of both the AUM and the uroplakin complex have remained enigmatic due to the paucity of high-resolution structural data. In this study, we utilized cryo-electron microscopy to elucidate the three-dimensional structure of the uroplakin complex within the porcine AUM. While the global resolution achieved was 3.5 Å, we acknowledge that due to orientation bias, the resolution in the vertical direction was determined to be 6.3 Å. Our findings unveiled that the uroplakin complexes are situated within hexagonally arranged crystalline lipid membrane domains, rich in hexosylceramides. Moreover, our research rectifies a misconception in a previous model by confirming the existence of a domain initially believed to be absent, and pinpointing the accurate location of a crucial Escherichia coli binding site implicated in urinary tract infections. These discoveries offer valuable insights into the molecular underpinnings governing the permeability barrier function of the urothelium and the orchestrated lipid phase formation within the plasma membrane.
Subject(s)
Membrane Proteins , Urothelium , Swine , Animals , Membrane Proteins/metabolism , Urothelium/chemistry , Urothelium/metabolism , Membrane Glycoproteins/metabolism , Cryoelectron Microscopy , Urinary Bladder , Uroplakins/analysis , Uroplakins/metabolism , Escherichia coli/metabolism , Lipids/analysisABSTRACT
As for the Bethesda system for cervical and thyroid cytopathology, a terminology for reporting urinary cytology has been published in 2015. The new "Paris System" provides a consensus terminology for urinary cytology which underlines the criteria for the recognition of high-grade urothelial carcinoma (HGUC) and of those excluding HGUC, or suspicious for HGUC. It also focuses on new rules to recognize and report the subgroup of "atypical urothelial cells". Here we describe and illustrate the various categories as in the reference book. We analyse the main diagnostic criteria, including microscopic features as well as the risk of malignancy associated to every diagnostic category.
