Kidney Week

Abstract: PO1101

Molecular Insights into the Structural and Dynamical Changes of Calcium Channel TRPV6 Induced by Its Interaction with Phosphatidylinositol 4,5-Bisphosphate

Session Information

• Fluid, Electrolyte, and Acid-Base Disorders: Basic
  November 04, 2021 | Location: On-Demand, Virtual Only
  Abstract Time: 10:00 AM - 12:00 PM

Category: Fluid, Electrolyte, and Acid-Base Disorders

• 901 Fluid, Electrolyte, and Acid-Base Disorders: Basic

Authors

• Wang, Lingyun, Divison of Nephrology, Department of Medicine, Nephrology Research and Training Center, University of Alabama at Birmingham, Birmingham, Alabama, United States

Lingyun Wang, PhD

• Cai, Ruiqi, Membrane Protein Disease Research Group, Department of Physiology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada

Ruiqi Cai,

• Chen, Xing-Zhen, Membrane Protein Disease Research Group, Department of Physiology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada

Xing-Zhen Chen,

• Peng, Ji-Bin, Divison of Nephrology, Department of Medicine, Nephrology Research and Training Center, University of Alabama at Birmingham, Birmingham, Alabama, United States

Ji-Bin Peng,

Background

Transient receptor potential vanilloid subfamily member 6 (TRPV6) is a Ca²⁺-selective channel that mediates Ca²⁺ entry into epithelial cells as the first step of the transcellular Ca²⁺ transport pathway. TRPV6 is expressed in the kidney, intestine, and other epithelial tissues, and the dysregulation of this channel has been implicated in cancers. TRPV6 and its close homologue TRPV5 are activated by phosphatidylinositol 4,5-bisphosphate (PIP₂); however, it is less clear how PIP₂ activates TRPV6 at the molecular level.

Methods

Recently, a structure of rabbit TRPV5 in complex with dioctanoyl (diC8) PIP₂, a soluble form of PIP₂, was determined by cryo-electron microscopy. Based on this structure, a structural model of human TRPV6 with PIP₂ was set up. This model was then embedded in a 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) lipid bilayer with water molecules added on both sides of the bilayer using CHARMM-GUI. Using the AMBER18 software, three 500-ns molecular dynamics simulations were performed for the two systems of TRPV6 with and without PIP₂.

Results

Interaction energy analyses show that the positively charged residues K300, R302, R305, K484, and R584 of TRPV6 play important roles in the binding of PIP₂, which is consistent with the structural data that residues R302 and K484 in TRPV5 are responsible for the binding of diC8 PIP₂. The binding of PIP₂ to TRPV6 increases the distance between the diagonally opposed residues D542 in the selectivity filter as well as the distance between the diagonally opposed residues M578 in the lower gate. Secondary structure and density analyses show that residue M578 in TRPV6 in the presence of PIP₂ undergoes structural and position changes, suggesting the opening of the lower gate. Principal component analysis also indicates that the binding of PIP₂ increases the dynamic motion of both the selectivity filter and the lower gate of TRPV6.

Conclusion

Simulation results indicate that PIP₂ increases the fluctuation of the key residues in both the selectivity filter and the lower gate of TRPV6. In addition, PIP₂ reduces the helix occupancy of a key residue in the lower gate. Furthermore, the diameters of both the selectivity filter and the lower gate are increased by PIP₂. These changes likely contribute to the opening of the TRPV6 channel.

Funding

• NIDDK Support