Strong homophilic interactions of the Ig-like domains of polycystin-1, the protein product of an autosomal dominant polycystic kidney disease gene, PKD1.
The 14 kb mRNA of the polycystic kidney disease gene PKD1 encodes a novel large (approximately 460 kDa) protein, polycystin-1, of unknown function that is responsible for autosomal dominant polycystic kidney disease (ADPKD). The unique organization of multiple adhesive domains of polycystin-1, including 16 Ig-like domains (or PKD domains) suggests that it may play an important role in cell-cell/cell-matrix interactions. Here we demonstrate the localization of polycystin-1 to epithelial cell-cell contacts in culture. These results along with structural predictions prompted us to propose that polycystin-1 is involved in cell-cell adhesion through its cluster of Ig-like repeats. We show that Ig-like domains II-XVI are involved in strong calcium-independent homophilic interactions in vitro. Domains XI-XVI form interactions with high affinity (K(d) = 60 nM) and domains II-V exhibit the lowest binding affinity (K(d) = 730 nM) in these studies. Most importantly, we show that antibodies raised against Ig-like domains of polycystin-1 disrupt cell-cell interactions in MDCK cell monolayers, thus indicating that polycystin-1 is directly involved in the cell-cell adhesion process. Collectively, these data suggest that interactions of the Ig-like repeats of polycystin-1 play an important role in mediating intercellular adhesion. We suggest that the loss of these interactions due to mutations in polycystin-1 may be an important step in cystogenesis.
Ibraghimov-Beskrovnaya
O
O
Genzyme Corporation, Framingham, MA 01701-9322, USA. oxana.ibraghimov@genzyme.com
Bukanov
N O
NO
Donohue
L C
LC
Dackowski
W R
WR
Klinger
K W
KW
Landes
G M
GM
D000818:Animals; D000906:Antibodies / Q000276:immunology; D001665:Binding Sites; D001667:Binding, Competitive; D002448:Cell Adhesion; D002460:Cell Line; D005455:Fluorescent Antibody Technique; D007700:Kinetics; D016891:Polycystic Kidney, Autosomal Dominant / Q000235:genetics*; D011506:Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D050396:TRPP Cation Channels
D000906:Antibodies; D011506:Proteins; D011993:Recombinant Fusion Proteins; D050396:TRPP Cation Channels