IFT88 influences chondrocyte actin organization and biomechanics

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• 作者：Z. Wang^&dagger ; ; A.K.T. Wann^&Dagger ; ; C.L. Thompson^&dagger ; ; ^{clare.l.thompson@qmul.ac.uk" class="auth_mail" title="E-mail the corresponding author} ; A. Hassen^&dagger ; ; W. Wang^&dagger ; ; M.M. Knight^&dagger ;
• 关键词：ITF88 ; F-actin ; Myosin IIB ; Cell mechanics ; Micropipette aspiration
• 刊名：Osteoarthritis and Cartilage
• 出版年：2016
• 出版时间：March 2016
• 年：2016
• 卷：24
• 期：3
• 页码：544-554
• 全文大小：3631 K

文摘

Primary cilia are microtubule based organelles which control a variety of signalling pathways important in cartilage development, health and disease. This study examines the role of the intraflagellar transport (IFT) protein, IFT88, in regulating fundamental actin organisation and mechanics in articular chondrocytes.

Methods

The study used an established chondrocyte cell line with and without hypomorphic mutation of IFT88 (IFT88^orpk). Confocal microscopy was used to quantify F-actin and myosin IIB organisation. Viscoelastic cell and actin cortex mechanics were determined using micropipette aspiration with actin dynamics visualised in live cells transfected with LifeACT-GFP.

Results

IFT88^orpk cells exhibited a significant increase in acto-myosin stress fibre organisation relative to wild-type (WT) cells in monolayer and an altered response to cytochalasin D. Rounded IFT88^orpk cells cultured in suspension exhibited reduced cortical actin expression with reduced cellular equilibrium modulus. Micropipette aspiration resulted in reduced membrane bleb formation in IFT88^orpk cells. Following membrane blebbing, IFT88^orpk cells exhibited slower reformation of the actin cortex. IFT88^orpk cells showed increased actin deformability and reduced cortical tension confirming that IFT regulates actin cortex mechanics. The reduced cortical tension is also consistent with the reduced bleb formation.

Conclusions

This study demonstrates for the first time that the ciliary protein IFT88 regulates fundamental actin organisation and the stiffness of the actin cortex leading to alterations in cell deformation, mechanical properties and blebbing in an IFT88 chondrocyte cell line. This adds to the growing understanding of the role of primary cilia and IFT in regulating cartilage biology.