A Structural Model of the TRPP2/PKD1 C-Terminal Coiled Coil Complex Obtained by a Combination of Computational and Experimental Approaches

Abstract

Autosomal dominant polycystic kidney disease (ADPKD) is caused by mutations in the genes encoding TRPP2 and PKD1, which form an ion channel/receptor complex containing three TRPP2 and one PKD1. PKD1 is a large integral membrane protein containing 11 putative transmembrane regions, while TRPP2 has 6 transmembrane regions and belongs to the transient receptor potential (TRP) channel family. TRPP2 and PKD1 associate through their C-termini, where a single PKD1 coiled coil binds to a TRPP2 coiled coil trimer. Many ADPKD pathogenic mutations result in the abolishment of the TRPP2/PKD1 coiled coil complex. Obtaining the structure of this complex would help us better understand its crucial role in the assembly and function of the full length TRPP2/PKD1 complex. By combing computational and experimental approaches, we generated a structural model for this coiled coil complex, based on a crystal structure of the TRPP2 coiled coil trimer. The structural model was constructed by a two-step docking strategy, which combines iterative rigid-body search and molecular dynamics (MD) simulations. In this structural model, the N-terminal region of the TRPP2 coiled coil remains as a trimer, but the C-terminal regions of two of the three TRPP2 helixes interact with a single PKD1 coiled coil to form a new trimer. Disruption of predicted critical TRPP2/PKD1 interface contacts abolished or greatly weakened the association between TRP2 and PKD1 coiled coils, supporting the accuracy of the structural model. Some mutations also greatly attenuated the assembly of the full-length TRPP2/PKD1 complex, providing the means to specifically disrupt this complex and study its functional importance in vitro and in vivo. The structural model also sheds light on the pathogenic mechanisms of some ADPKD-causing mutations.∗J.Z. and Y.Y. contributed equally to this work.