Intracellular and extracellular forces drive primary cilia movement

Area of Science:

• Cell Biology
• Biophysics

Background:

• Primary cilia are microtubule-based organelles crucial for sensory transduction.
• Their mechanical properties and contribution to cellular perception remain largely unknown.
• Kidney epithelial cells utilize primary cilia for sensing fluid flow.

Purpose of the Study:

• To investigate the mechanical and structural properties of primary cilia in kidney epithelial cells.
• To understand how these properties influence ciliary sensory functions.

Main Methods:

• Optical trapping was used to manipulate primary cilia from Madin-Darby canine kidney-II (MDCK-II) cells.
• 3D tracking analyzed ciliary and basal body movements.
• Bending rigidity was calculated to assess mechanical properties.

Main Results:

• Primary cilia bend along their length and pivot around a basal body hinge.
• Calculated bending rigidity suggests weak microtubule doublet coupling.
• Active ciliary motility was observed, correlated with basal body fluctuations.
• Motility depended on ATP and cytoplasmic myosin-II.

Conclusions:

• Actin cytoskeleton forces surrounding the basal body drive active ciliary movement.
• This actin-driven motility may tune and calibrate primary cilia's sensory roles.
• Understanding ciliary mechanics is key to deciphering cellular sensory mechanisms.