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Abstract: FR-PO274

Protein 4.1O Binds to Polycystin-1, Activates Ubiquitination, and Inhibits Polycystin-1 Signaling

Session Information

Category: Genetic Diseases of the Kidneys

  • 1101 Genetic Diseases of the Kidneys: Cystic


  • Vienken, Theresia, Heinrich-Heine-Universitat Dusseldorf, Dusseldorf, Nordrhein-Westfalen, Germany
  • Koenigshausen, Eva, Heinrich-Heine-Universitat Dusseldorf, Dusseldorf, Nordrhein-Westfalen, Germany
  • Rump, Lars C., Heinrich-Heine-Universitat Dusseldorf, Dusseldorf, Nordrhein-Westfalen, Germany
  • Sellin, Lorenz, Heinrich-Heine-Universitat Dusseldorf, Dusseldorf, Nordrhein-Westfalen, Germany

The majority of ADPKD patients have a PKD1 gene mutation. PKD1 codes for Polycystin-1 (PC-1). Cyst formation is caused by altered renal tubular cell proliferation and migration. Protein 4.1 family members are actin adaptors, which link plasma membrane receptors to the actin cytoskeleton. Protein 4.1O (FRMD3) is a candidate gene for diabetic nephropathy. Furthermore, protein 4.1O has properties of a tumor suppressor. This study investigates the molecular and cellular properties of protein 4.1O as a potential ADPKD modifier and therapeutic target.


PC-1 full-length and truncation mutants were transiently expressed. PC-1 interaction with protein 4.1O and its truncation mutants were investigated. Truncation mutants cover the N- and C-terminal domains of protein 4.1O (Band 4.1, FERM, actin-binding domain and coiled coil domain). The modulation of the PC-1 signaling properties by protein 4.1O were investigated in luciferase assays for c-myc and TEAD. FRMD3 core promotor regions were cloned into luciferase reporter and its activation by PC-1 was investigated. Ubiquitination assays investigated the influence of protein 4.1O on ubiquitination of itself and other proteins.


Coimmunoprecipitations show an interaction of protein 4.1O to PC-1. The C-terminus of PC-1 interacts with isoforms of protein 4.1O (201, 204, 207). The truncation mapping and isoform alignment identfies a potential leucine zipper domain in protein 4.1O as the C-terminal binding domain to PC-1. The N-terminal FERM domain and the C-terminal domain of protein 4.1O are each by themselves sufficient to mediate PC-1 interaction. Protein 4.1O silences the PC-1 mediated transactivation of c-myc and hippo signaling (TEAD). PC-1 activates the protein 4.1O promotor. Furthermore, protein 4.1O enhances ubiquitination and is polyubiquitilated.


Both, the FERM domain and C-terminal domain, containing the coiled coil domain, of protein 4.1O interact with the PC-1 C-terminus. The protein 4.1O interaction inhibits the PC-1 mediated activation of c-myc and hippo signaling. PC-1 activates the promotor of protein 4.1O and mediates silencing of PC-1 signaling. Furthermore, protein 4.1O enhances ubiquitination and its own polyubiqitination. In summary, protein 4.1O shows features of an anti-cystogenic protein and might be an ADPKD modifier.