Structural and compositional diversity in the kainate receptor family

Area of Science:

• Neuroscience
• Molecular Biology
• Biochemistry

Background:

• Kainate receptors (KARs) are ionotropic glutamate receptors crucial for synaptic transmission.
• KARs assemble into tetramers from five subunits (GluK1-5), but their compositional diversity remains largely unknown.

Purpose of the Study:

• To elucidate the structural compatibility and assembly rules of KAR subunits.
• To investigate the diversity of KAR subunit combinations and stoichiometry in native systems.

Main Methods:

• Determined the structure of the GluK1 homomer to assess subunit compatibility.
• Analyzed single-cell RNA sequencing data to identify co-expression patterns of KAR subunits.
• Employed single-molecule fluorescence techniques to analyze the composition and stoichiometry of KAR complexes.

Main Results:

• Extreme diversity in co-expression of two or more KAR subunits within single cells was observed.
• Di-heteromeric KARs (GluK1/K2, GluK1/K3, GluK2/K3) can form with all possible stoichiometries.
• Specific di-heteromers (GluK1/K5, GluK2/K5, GluK3/K5) form 3:1 or 2:2 complexes.
• KARs can assemble into tri- and tetra-heteromeric complexes.

Conclusions:

• KARs display extensive compositional and stoichiometric diversity, exceeding previous assumptions.
• The findings provide a foundation for understanding KAR function in complex neural circuits.
• This study reveals novel, highly complex KAR assemblies, including tri- and tetra-heteromers.