Force-response considerations in ciliary mechanosensation

¹ Case Western Reserve University

^* To whom correspondence should be addressed. E-mail: andy.resnick{at}case.edu.

Submitted on January 22, 2007
Revised on February 24, 2007
Accepted on 23 April 2007

	Abstract

Considerable experimental evidence indicates that the primary, non-motile cilium is a mechanosensory organelle in several epithelial cell types. As the relationship between cellular responses and nature and magnitude of applied forces is not well understood, we have investigated the effects of exposure of monolayers of renal collecting duct chief cells to orbital shaking and quantified the forces incident on cilia. 24 hr exposure of these cells to orbital shaking resulted in a decrease of amiloride-sensitive sodium current by about 60% and ciliary length by about 30%. The sensitivity of the sodium current to shaking was dependent on intact cilia. The drag force on cilia due to induced fluid flow during orbital shaking was estimated at maximally 5.2*10^-3 pN at 2 Hz, about 4 times that of thermal noise. The major structural feature of cilia contributing to their sensitivity appears to be ciliary length. As more than half of the total drag force is exerted on the ciliary cap, one function of the slender stalk may be to expose the cap to greater drag force. Regardless, the findings indicate that the cilium is a mechanosensory organelle with a sensitivity much lower than previously recognized.

Key Words: fluid flow, mechanosensation, mechanotransduction, primary cilium

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