Annexin A5 Interacts with Polycystin-1 and Interferes with the Polycystin-1 Stimulated Recruitment of E-cadherin into Adherens Junctions Arseni Markoff 1 ⁎, Nadia Bogdanova 2 , Markus Knop 1 , Claas Rüffer 1 Heidi Kenis 3 , Petra Lux 3 , Chris Reutelingsperger 3 , Vassil Todorov 4 Bernd Dworniczak 2 , Jürgen Horst 2 and Volker Gerke 1 1 Institute of Medical Biochemistry, Westfalian- Wilhelms University of Muenster, Von Esmarch Str. 56, 48149 Muenster, Germany 2 Institut für Humanegenetik, University Clinics Muenster , Vesaliusweg 12-14, 48149 Muenster, Germany 3 Department of Biochemistry, Cardiovascular Research Institute Maastricht, P.O. Box 616, 6200 MD Maastricht, Netherlands 4 Clinic of Nephrology and Haemodialysis, Medical University, Pleven, Bulgaria Polycystin-1 is the gene product of PKD1, the first gene identified to be causative for the condition of autosomal dominant polycystic kidney disease (ADPKD). Mutations in PKD1 are responsible for the majority of ADPKD cases worldwide. Polycystin-1 is a protein of the transient receptor potential channels superfamily, with 11 transmembrane spans and an extracellular N-terminal region of ∼ 3109 amino acid residues, harboring multiple putative ligand binding domains. We demonstrate here that annexin A5 (ANXA5), a Ca 2+ and phospholipid binding protein, interacts with the N-terminal leucine-rich repeats of polycystin-1, in vitro and in a cell culture model. This interaction is direct and specific and involves a conserved sequence of the ANXA5 N-terminal domain. Using Madin-Darby canine kidney cells expressing polycystin-1 in an inducible manner we also show that polycystin-1 colocalizes with E-cadherin at cell–cell contacts and accelerates the recruitment of intracellular E-cadherin to reforming junctions. This polycystin-1 stimulated recruitment is significantly delayed by extracellular annexin A5. © 2007 Elsevier Ltd. All rights reserved. *Corresponding author Keywords: ANXA5; annexin A5; PKD1; polycystin-1; E-cadherin Introduction Polycystins-1 and - 2 are the respective products of PKD1 and PKD2, genes responsible for the condi- tion of autosomal dominant polycystic kidney disease (ADPKD). PKD1 mutations cause ADPKD in the majority of cases, leading to severe impairment of kidney function and accompanying systemic damage. 1,2 Both polycystins interact via their cyto- solic C-terminal regions 3,4 and are integral parts of a common signal transduction pathway. 1 Polycystin-1 (TRPP1) is the only 11 transmembrane domains- containing protein that belongs to the superfamily of transient receptor potential channels (TRPs), nor- mally characterized by six transmembrane spans. Recent studies support possible mechanosensory function for TRPP1, which can be mediated by elastic properties of the extracellular region. 5 The assembly of polycystins-1 and - 2 at the plasma membrane, when co-expressed in cultured CHO cells, has been reported to produce unique Ca 2+ -permeable non- selective currents. 6 Moreover, recent studies demon- strate that the expression of polycystin-1 alone can result in such cation currents. 7 Polycystin-1 consists of a large, extracellular N- terminal region of ∼ 3109 amino acid residues, 11 predicted transmembrane domains (∼ 993 amino acid residues), and a short, cytosolic C-terminal por- tion (∼ 200 amino acid residues). 8,9 The N-terminal sequence of the protein harbors several domains predicted to represent ligand interaction sites: two leucine-rich repeats (LRRs), a C-type lectin domain, an LDL-A like domain, 15 copies of PKD domains, which are immunoglobulin (Ig)-like repeats, and a region homologous to the sea urchin sperm protein, REJ. 9 The protein is cleaved specifically at position T3049, which releases an extracellular N-terminal Abbreviations used: ADPKD, autosomal dominant polycystic kidney disease; LRR, leucine-rich repeat; GCT, glutathione-S-transferase. E-mail address of the corresponding author: markoff@uni-muenster.de doi:10.1016/j.jmb.2007.03.070 J. Mol. Biol. (2007) 369, 954–966 0022-2836/$ - see front matter © 2007 Elsevier Ltd. All rights reserved.