IFT88-KAP interaction defines a conserved mechanism for kinesin-2-IFT coupling

Area of Science:

• Cell Biology
• Molecular Biology
• Structural Biology

Background:

• Kinesin-2 motors are crucial for intraflagellar transport (IFT), a process vital for building cilia.
• The molecular mechanism connecting kinesin-2 to the IFT machinery has been unclear.

Purpose of the Study:

• To elucidate the structural and molecular basis of kinesin-2 recruitment to the IFT machinery.
• To identify the specific protein interactions mediating motor-cargo coupling for ciliary assembly.

Main Methods:

• Utilized AlphaFold modeling to predict protein structures.
• Performed site-directed mutagenesis in *C. elegans* and human cell lines.
• Conducted rescue experiments to assess functional impact.

Main Results:

• Identified IFT88 as a direct adaptor protein linking kinesin-2 to the IFT complex.
• Characterized a conserved electrostatic interface between IFT88's tetratricopeptide repeats (TPRs) and kinesin-2's KAP subunit armadillo (ARM) repeats.
• Demonstrated that this core interface is essential for motor binding and processive IFT, with mutations disrupting ciliary localization in both model organisms and human cells.

Conclusions:

• Defined the molecular mechanism of kinesin-2/IFT association.
• Established IFT88-KAP interaction as a conserved hub critical for ciliary assembly and function.
• The TPR-ARM architecture represents an evolutionarily preserved module for motor-cargo coupling.