title: Functional analysis of PKD1 transgenic lines reveals a direct role for polycystin-1 in mediating cell-cell adhesion.
abstract: The PKD1 protein, polycystin-1, is a large transmembrane protein of uncertain function and topology. To study the putative functions of polycystin-1, conditionally immortalized kidney cells transgenic for PKD1 were generated and an interaction between transgenic polycystin-1 and endogenous polycystin-2 has been recently demonstrated in these cells. This study provides the first functional evidence that transgenic polycystin-1 directly mediates cell-cell adhesion. In non-permeabilized cells, polycystin-1 localized to the lateral cell borders with N-terminal antibodies but not with a C-terminal antibody; there was a clear difference in surface intensity between transgenic and non-transgenic cells. Compared with non-transgenic cells, transgenic cells showed a dramatic increase in resistance to the disruptive effect of a polycystin-1 antibody raised to the PKD domains of polycystin-1 (IgPKD) in both cell adhesion and cell aggregation assays. The differential effect on cell adhesion between transgenic and non-transgenic cells could be reproduced using recombinant fusion proteins encoding non-overlapping regions of the IgPKD domains. In contrast, antibodies raised to other extracellular domains of polycystin-1 had no effect on cell adhesion. Finally, the specificity of this finding was confirmed by the lack of effect of IgPKD antibody on cell adhesion in a PKD1 cystic cell line deficient in polycystin-1. These results demonstrate that one of the primary functions of polycystin-1 is to mediate cell-cell adhesion in renal epithelial cells, probably via homophilic or heterophilic interactions of the PKD domains. Disruption of cell-cell adhesion during tubular morphogenesis may be an early initiating event for cyst formation in ADPKD.
authors.affiliation: Sheffield Kidney Institute, Division of Clinical Sciences (North), University of Sheffield, Clinical Sciences Centre, Northern General Hospital, Herries Road, Sheffield S5 7AU, UK.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Streets
authors.forename: Linda J
authors.initials: LJ
authors.lastname: Newby
authors.forename: Michael J
authors.initials: MJ
authors.lastname: O'Hare
authors.forename: Nikolay O
authors.initials: NO
authors.lastname: Bukanov
authors.forename: Oxana
authors.initials: O
authors.lastname: Ibraghimov-Beskrovnaya
authors.forename: Albert C M
authors.initials: AC
authors.lastname: Ong
mesh_terms: D000818:Animals; D017209:Apoptosis; D002448:Cell Adhesion; D002449:Cell Aggregation; D002460:Cell Line; D002470:Cell Survival; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D020287:In Situ Nick-End Labeling; D007668:Kidney / Q000166:cytology; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D008856:Microscopy, Fluorescence; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000235:genetics* / Q000502:physiology*; D012333:RNA, Messenger / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D050396:TRPP Cation Channels
chemical_list: D005982:Glutathione Transferase; D008565:Membrane Proteins; D011506:Proteins; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D050396:TRPP Cation Channels