Skip to main content
NCBI home page
The Journal of Cell Biology logoLink to The Journal of Cell Biology
. 1990 Sep 1;111(3):1207–1216. doi: 10.1083/jcb.111.3.1207

Uroplakin I: a 27-kD protein associated with the asymmetric unit membrane of mammalian urothelium

PMCID: PMC2116275  PMID: 1697295

Abstract

The luminal surface of mammalian urothelium is covered with numerous plaques (also known as the asymmetric unit membrane or AUM) composed of semi-crystalline, hexagonal arrays of 12-nm protein particles. Despite the presumed importance of these plaques in stabilizing the urothelial surface during bladder distention, relatively little is known about their protein composition. Using a mouse mAb, AE31, we have identified a 27-kD protein that is urothelium-specific and is differentially expressed in superficial umbrella cells. This protein (pI approximately 5.8) partitions into the detergent phase during Triton X-114 phase separation. Pulse-chase experiments using cultured bovine urothelial cells showed that this protein is synthesized as a 32-kD precursor that is processed through a 30-kD intermediate, to the mature 27-kD form. In cytoplasmic vesicles containing immature AUM, the AE31 epitope is detected in patches on the cytoplasmic side, but in mature, apical AUM it is detected exclusively on the luminal side. This suggests an unusual translocation of the AE31 epitope during AUM maturation; more data are required, however, to substantiate this interpretation. Immunoaffinity purification of the 27-kD protein results in the copurification in approximately molar ratio of a 15-kD protein, as well as a small and variable amount of a 47-kD protein. Immunoblotting data indicate that these three proteins are immunologically distinguishable. This copurified 15-kD protein is relative basic (pI approximately 8.0). Like the 27-kD protein, it is urothelium-specific and is present mainly in the umbrella cells. Together, our data indicate that a 27-kD protein is urothelial plaque-associated (uroplakin I). Based on complex formation data, we provisionally name the 15-kD protein uroplakin II; additional data will be required to determine whether this and the 47- kD protein are integral parts of AUM. The identification of these AUM- associated and -related proteins, plus the availability of a culture system capable of synthesizing and processing some of these molecules, offer new opportunities for studying the detailed structure, assembly, and function of asymmetrical unit membrane.

Full Text

The Full Text of this article is available as a PDF (2.7 MB).

Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Alroy J., Merk F. B., Morré D. J., Weinstein R. S. Membrane differentiation in the Golgi apparatus of mammalian urinary bladder epithelium. Anat Rec. 1982 Aug;203(4):429–440. doi: 10.1002/ar.1092030402. [DOI] [PubMed] [Google Scholar]
  2. Armstrong J. M., Newman J. D. A simple, rapid method for the preparation of plasma membranes from liver. Arch Biochem Biophys. 1985 May 1;238(2):619–628. doi: 10.1016/0003-9861(85)90207-3. [DOI] [PubMed] [Google Scholar]
  3. Bordier C. Phase separation of integral membrane proteins in Triton X-114 solution. J Biol Chem. 1981 Feb 25;256(4):1604–1607. [PubMed] [Google Scholar]
  4. Brisson A., Wade R. H. Three-dimensional structure of luminal plasma membrane protein from urinary bladder. J Mol Biol. 1983 May 5;166(1):21–36. doi: 10.1016/s0022-2836(83)80048-5. [DOI] [PubMed] [Google Scholar]
  5. Caruthers J. M., Bonneville M. A. The asymmetric unit membrane (AUM) structure in the lumenal plasma membrane of urothelium: the effect of trypsin on the integrity of the plaques. J Ultrastruct Res. 1980 Jun;71(3):288–302. doi: 10.1016/s0022-5320(80)90080-5. [DOI] [PubMed] [Google Scholar]
  6. Caruthers J. S., Bonneville M. A. Isolation and characterization of the urothelial lumenal plasma membrane. J Cell Biol. 1977 May;73(2):382–399. doi: 10.1083/jcb.73.2.382. [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. Chlapowski F. J., Bonneville M. A., Staehelin L. A. Lumenal plasma membrane of the urinary bladder. II. Isolation and structure of membrane components. J Cell Biol. 1972 Apr;53(1):92–104. doi: 10.1083/jcb.53.1.92. [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. Doran T. I., Vidrich A., Sun T. T. Intrinsic and extrinsic regulation of the differentiation of skin, corneal and esophageal epithelial cells. Cell. 1980 Nov;22(1 Pt 1):17–25. doi: 10.1016/0092-8674(80)90150-6. [DOI] [PubMed] [Google Scholar]
  9. Eichner R., Bonitz P., Sun T. T. Classification of epidermal keratins according to their immunoreactivity, isoelectric point, and mode of expression. J Cell Biol. 1984 Apr;98(4):1388–1396. doi: 10.1083/jcb.98.4.1388. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Hicks R. M., Ketterer B. Hexagonal lattice of subunits in the thick luminal membrane of the rat urinary bladder. Nature. 1969 Dec 27;224(5226):1304–1305. doi: 10.1038/2241304a0. [DOI] [PubMed] [Google Scholar]
  11. Hicks R. M., Ketterer B. Isolation of the plasma membrane of the luminal surface of rat bladder epithelium, and the occurrence of a hexagonal lattice of subunits both in negatively stained whole mounts and in sectioned membranes. J Cell Biol. 1970 Jun;45(3):542–553. doi: 10.1083/jcb.45.3.542. [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. Hicks R. M. The fine structure of the transitional epithelium of rat ureter. J Cell Biol. 1965 Jul;26(1):25–48. doi: 10.1083/jcb.26.1.25. [DOI] [PMC free article] [PubMed] [Google Scholar]
  13. Hicks R. M. The function of the golgi complex in transitional epithelium. Synthesis of the thick cell membrane. J Cell Biol. 1966 Sep;30(3):623–643. doi: 10.1083/jcb.30.3.623. [DOI] [PMC free article] [PubMed] [Google Scholar]
  14. Hicks R. M. The permeability of rat transitional epithelium. Kertinization and the barrier to water. J Cell Biol. 1966 Jan;28(1):21–31. doi: 10.1083/jcb.28.1.21. [DOI] [PMC free article] [PubMed] [Google Scholar]
  15. Ketterer B., Hicks R. M., Christodoulides L., Beale D. Studies of the chemistry of the luminal plasma membrane of rat bladder epithelial cells. Biochim Biophys Acta. 1973 Jun 22;311(2):180–190. doi: 10.1016/0005-2736(73)90265-4. [DOI] [PubMed] [Google Scholar]
  16. Knutton S., Robertson J. D. Regular structures in membranes: the lumenal plasma membrane of the cow urinary bladder. J Cell Sci. 1976 Nov;22(2):355–370. doi: 10.1242/jcs.22.2.355. [DOI] [PubMed] [Google Scholar]
  17. Koss L. G. The asymmetric unit membranes of the epithelium of the urinary bladder of the rat. An electron microscopic study of a mechanism of epithelial maturation and function. Lab Invest. 1969 Aug;21(2):154–168. [PubMed] [Google Scholar]
  18. Köhler G., Milstein C. Continuous cultures of fused cells secreting antibody of predefined specificity. Nature. 1975 Aug 7;256(5517):495–497. doi: 10.1038/256495a0. [DOI] [PubMed] [Google Scholar]
  19. Laemmli U. K. Cleavage of structural proteins during the assembly of the head of bacteriophage T4. Nature. 1970 Aug 15;227(5259):680–685. doi: 10.1038/227680a0. [DOI] [PubMed] [Google Scholar]
  20. Lewis S. A., de Moura J. L. Apical membrane area of rabbit urinary bladder increases by fusion of intracellular vesicles: an electrophysiological study. J Membr Biol. 1984;82(2):123–136. doi: 10.1007/BF01868937. [DOI] [PubMed] [Google Scholar]
  21. Minsky B. D., Chlapowski F. J. Morphometric analysis of the translocation of lumenal membrane between cytoplasm and cell surface of transitional epithelial cells during the expansion-contraction cycles of mammalian urinary bladder. J Cell Biol. 1978 Jun;77(3):685–697. doi: 10.1083/jcb.77.3.685. [DOI] [PMC free article] [PubMed] [Google Scholar]
  22. O'Farrell P. Z., Goodman H. M., O'Farrell P. H. High resolution two-dimensional electrophoresis of basic as well as acidic proteins. Cell. 1977 Dec;12(4):1133–1141. doi: 10.1016/0092-8674(77)90176-3. [DOI] [PubMed] [Google Scholar]
  23. Pfeffer S. R., Rothman J. E. Biosynthetic protein transport and sorting by the endoplasmic reticulum and Golgi. Annu Rev Biochem. 1987;56:829–852. doi: 10.1146/annurev.bi.56.070187.004145. [DOI] [PubMed] [Google Scholar]
  24. Porter K. R., Kenyon K., Badenhausen S. Specializations of the unit membrane. Protoplasma. 1967;63(1):262–274. [PubMed] [Google Scholar]
  25. Randall L. L., Hardy S. J. Unity in function in the absence of consensus in sequence: role of leader peptides in export. Science. 1989 Mar 3;243(4895):1156–1159. doi: 10.1126/science.2646712. [DOI] [PubMed] [Google Scholar]
  26. Rheinwald J. G., Green H. Serial cultivation of strains of human epidermal keratinocytes: the formation of keratinizing colonies from single cells. Cell. 1975 Nov;6(3):331–343. doi: 10.1016/s0092-8674(75)80001-8. [DOI] [PubMed] [Google Scholar]
  27. Robertson J. D. The structure of biological membranes. Current status. Arch Intern Med. 1972 Feb;129(2):202–228. [PubMed] [Google Scholar]
  28. Robertson J. D., Vergara J. Analysis of the structure of intramembrane particles of the mammalian urinary bladder. J Cell Biol. 1980 Aug;86(2):514–528. doi: 10.1083/jcb.86.2.514. [DOI] [PMC free article] [PubMed] [Google Scholar]
  29. Rose J. K., Doms R. W. Regulation of protein export from the endoplasmic reticulum. Annu Rev Cell Biol. 1988;4:257–288. doi: 10.1146/annurev.cb.04.110188.001353. [DOI] [PubMed] [Google Scholar]
  30. Sabatini D. D., Kreibich G., Morimoto T., Adesnik M. Mechanisms for the incorporation of proteins in membranes and organelles. J Cell Biol. 1982 Jan;92(1):1–22. doi: 10.1083/jcb.92.1.1. [DOI] [PMC free article] [PubMed] [Google Scholar]
  31. Sarikas S. N., Chlapowski F. J. Effect of ATP inhibitors on the translocation of luminal membrane between cytoplasm and cell surface of transitional epithelial cells during the expansion-contraction cycle of the rat urinary bladder. Cell Tissue Res. 1986;246(1):109–117. doi: 10.1007/BF00219006. [DOI] [PubMed] [Google Scholar]
  32. Severs N. J., Hicks R. M. Analysis of membrane structure in the transitional epithelium of rat urinary bladder. 2. The discoidal vesicles and Golgi apparatus: their role in luminal membrane biogenesis. J Ultrastruct Res. 1979 Nov;69(2):279–296. doi: 10.1016/s0022-5320(79)90117-5. [DOI] [PubMed] [Google Scholar]
  33. Staehelin L. A., Chlapowski F. J., Bonneville M. A. Lumenal plasma membrane of the urinary bladder. I. Three-dimensional reconstruction from freeze-etch images. J Cell Biol. 1972 Apr;53(1):73–91. doi: 10.1083/jcb.53.1.73. [DOI] [PMC free article] [PubMed] [Google Scholar]
  34. Stubbs C. D., Ketterer B., Hicks R. M. The isolation and analysis of the luminal plasma membrane of calf urinary bladder epithelium. Biochim Biophys Acta. 1979 Nov 16;558(1):58–72. doi: 10.1016/0005-2736(79)90315-8. [DOI] [PubMed] [Google Scholar]
  35. Sun T. T., Doran T. I., Vidrich A. The use of antikeratin antibodies for the identification of cultured epithelial cells. Birth Defects Orig Artic Ser. 1980;16(2):183–196. [PubMed] [Google Scholar]
  36. Sun T. T., Green H. Immunofluorescent staining of keratin fibers in cultured cells. Cell. 1978 Jul;14(3):469–476. doi: 10.1016/0092-8674(78)90233-7. [DOI] [PubMed] [Google Scholar]
  37. Taylor K. A., Robertson J. D. Analysis of the three-dimensional structure of the urinary bladder epithelial cell membranes. J Ultrastruct Res. 1984 Apr;87(1):23–30. doi: 10.1016/s0022-5320(84)90113-8. [DOI] [PubMed] [Google Scholar]
  38. Towbin H., Staehelin T., Gordon J. Electrophoretic transfer of proteins from polyacrylamide gels to nitrocellulose sheets: procedure and some applications. Proc Natl Acad Sci U S A. 1979 Sep;76(9):4350–4354. doi: 10.1073/pnas.76.9.4350. [DOI] [PMC free article] [PubMed] [Google Scholar]
  39. Vergara J., Longley W., Robertson J. D. A hexagonal arrangement of subunits in membrane of mouse urinary bladder. J Mol Biol. 1969 Dec 28;46(3):593–596. doi: 10.1016/0022-2836(69)90200-9. [DOI] [PubMed] [Google Scholar]
  40. Warren R. C., Hicks R. M. Structure of the subunits in the thick luminal membrane of rat urinary bladder. Nature. 1970 Jul 18;227(5255):280–281. doi: 10.1038/227280b0. [DOI] [PubMed] [Google Scholar]
  41. Woodcock-Mitchell J., Eichner R., Nelson W. G., Sun T. T. Immunolocalization of keratin polypeptides in human epidermis using monoclonal antibodies. J Cell Biol. 1982 Nov;95(2 Pt 1):580–588. doi: 10.1083/jcb.95.2.580. [DOI] [PMC free article] [PubMed] [Google Scholar]
  42. Wu Y. J., Parker L. M., Binder N. E., Beckett M. A., Sinard J. H., Griffiths C. T., Rheinwald J. G. The mesothelial keratins: a new family of cytoskeletal proteins identified in cultured mesothelial cells and nonkeratinizing epithelia. Cell. 1982 Dec;31(3 Pt 2):693–703. doi: 10.1016/0092-8674(82)90324-5. [DOI] [PubMed] [Google Scholar]
  43. Xu S., Cramer W. A., Peterson A. A., Hermodson M., Montecucco C. Dynamic properties of membrane proteins: reversible insertion into membrane vesicles of a colicin E1 channel-forming peptide. Proc Natl Acad Sci U S A. 1988 Oct;85(20):7531–7535. doi: 10.1073/pnas.85.20.7531. [DOI] [PMC free article] [PubMed] [Google Scholar]

Articles from The Journal of Cell Biology are provided here courtesy of The Rockefeller University Press

RESOURCES