Kinesin-2 autoinhibition requires elbow phosphorylation

Area of Science:

• Cellular biology
• Molecular motors
• Biochemistry

Background:

• Kinesin motor proteins are essential for intracellular transport.
• Their activity is regulated by autoinhibition, but the mechanisms are unclear.
• Intraflagellar transport (IFT) kinesins, like OSM-3, are vital for cilia function.

Purpose of the Study:

• To investigate the regulatory mechanisms of kinesin autoinhibition.
• To identify the specific kinase and phosphorylation site involved in OSM-3 regulation.
• To understand the functional consequences of altered OSM-3 activity on cilia.

Main Methods:

• In vitro biochemical assays to test kinesin motility.
• Site-directed mutagenesis to create phosphor-dead (PD) and phosphor-mimic (PM) OSM-3 variants.
• Generation and analysis of knock-in C. elegans strains expressing mutant OSM-3.

Main Results:

• NEKL-3 kinase directly phosphorylates the elbow region of OSM-3.
• Phosphor-dead OSM-3 exhibits constitutive motility in vitro.
• Both PD and PM mutations shorten C. elegans sensory cilia.
• OSM-3PD accumulates in neurites and fails to enter cilia, while OSM-3PM enters cilia but moves slower.

Conclusions:

• Elbow phosphorylation by NEKL-3 acts as a key inhibitory mechanism for kinesin OSM-3.
• This phosphorylation is critical for proper intraflagellar transport and cilia maintenance.
• Dysregulation of this phosphorylation impacts kinesin localization and motor function, affecting cilia structure.