A novel PKD2L1 C-terminal domain critical for trimerization and channel function

Area of Science:

• Ion channel biophysics
• Molecular and cellular biology
• Physiology

Background:

• Polycystic kidney disease 2-like-1 (PKD2L1), a TRP channel, plays roles in development and taste.
• PKD2L1 forms heterotetramers with PKD1L3, but the mechanism of PKD2L1 oligomerization into functional channels is unclear.
• Previous studies suggested a C-terminal coiled-coil-2 (CC2) domain is important for trimerization, but its role in channel function was debated.

Purpose of the Study:

• To elucidate the molecular mechanisms underlying PKD2L1 protein oligomerization and channel function.
• To identify specific domains responsible for PKD2L1 homotrimerization and heterotetramer formation.
• To determine the role of identified domains in PKD2L1 channel activity.

Main Methods:

• Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and blue native PAGE to assess protein oligomerization.
• Site-directed mutagenesis to investigate the function of specific PKD2L1 domains.
• Electrophysiology and Xenopus oocyte expression systems to measure channel activity.
• Co-immunoprecipitation and dynamic light scattering to confirm protein interactions and oligomerization.

Main Results:

• A novel C-terminal domain, C1 (K575-T622), was identified as crucial for stronger PKD2L1 homotrimerization than the CC2 domain.
• The N-terminus of PKD2L1 was found to be critical for protein dimerization.
• Electrophysiological studies demonstrated that the C1 domain, but not CC2, is essential for PKD2L1 channel function.
• C1 domain peptides inhibited PKD2L1 trimerization and channel activity, supporting its role in oligomerization and function.
• Co-immunoprecipitation and dynamic light scattering experiments confirmed C1's involvement in trimerization.

Conclusions:

• The C1 domain is the first identified PKD2L1 domain essential for both protein trimerization and channel function.
• PKD2L1 and PKD2L1/PKD1L3 channels likely share a common PKD2L1 trimerization process mediated by the C1 domain.
• These findings provide critical insights into the structural basis of PKD2L1 channel assembly and activity.