Deciliation Is Associated with Dramatic Remodeling of Epithelial Cell Junctions and Surface Domains

Abstract

Stress-induced shedding of motile cilia (autotomy) has been documented in diverse organisms and likely represents a conserved cellular reaction. However, little is known about whether primary cilia are shed from mammalian epithelial cells and what impact deciliation has on polarized cellular organization. We show that several chemically distinct agents trigger autotomy in epithelial cells. Surprisingly, deciliation is associated with a significant, but reversible increase in transepithelial resistance. This reflects substantial reductions in tight junction proteins associated with "leaky" nephron segments (e.g., claudin-2). At the same time, apical trafficking of gp80/clusterin and gp114/CEACAM becomes randomized, basal-lateral delivery of Na,K-ATPase is reduced, and expression of the nonciliary apical protein gp135/podocalyxin is greatly decreased. However, ciliogenesis-impaired MDCK cells do not undergo continual junction remodeling, and mature cilia are not required for autotomy-associated remodeling events. Deciliation and epithelial remodeling may be mechanistically linked processes, because RNAi-mediated reduction of Exocyst subunit Sec6 inhibits ciliary shedding and specifically blocks deciliation-associated down-regulation of claudin-2 and gp135. We propose that ciliary autotomy represents a signaling pathway that impacts the organization and function of polarized epithelial cells.

Polycystin-2 and phosphodiesterase 4C are components of a ciliary A-kinase anchoring protein complex that is disrupted in cystic kidney diseases

“…S1C). To verify that the effects on cAMP were due to the loss of primary cilia, ciliated Kif3a F/-cells were deciliated with dibucaine (17). Treatment with dibucaine resulted in the removal of cilia from ∼95% of cells (Fig.…”

Coordination of Rab8 and Rab11 in primary ciliogenesis

“…The exocyst interacts with Rab11 and is implicated in the trafficking from the TGN (30) or recycling endosomes (24,31,32) to the plasma membrane. Recently, the exocyst has also been implicated in ciliogenesis (28,(33)(34)(35)(36). Future studies are needed to elucidate the molecular mechanisms by which the Rab proteins function together with the exocyst complex during primary ciliogenesis.…”

Aberrant Activation of Fatty Acid Synthesis Suppresses Primary Cilium Formation and Distorts Tissue Development

“…Our findings that enhanced fatty acid supply causes a dramatic flattening of the cells that is accompanied by mislocalization of apical proteins, together with recent reports that interference with apical protein transport impairs cell polarization and blocks ciliogenesis (27), suggest that perturbed apical protein transport and subsequent impairment of cell polarization may underlie defective ciliogenesis induced by activated lipogenesis. Conversely, as both phenomena are intricately linked (19,26), defective ciliogenesis may subsequently prevent proper cell polarization, which reinforces the phenotype. The significance of these findings is supported by the mounting evidence that defective cell polarization and loss of the primary cilium often accompany cancer progression (24,(32)(33)(34)(35).…”

“…The apical marker gp135/podocalyxin partially disappeared in nSREBP1c-transduced cells, which is a phenomenon that has been linked to mislocalization of the protein (26,28). Interestingly, these changes were reversed when cells were treated with soraphen A and were also induced in nontransfected cells exposed to exogenous palmitic acid.…”

“…In several experimental systems, cilium formation is considered the terminal stage of cell polarization, and conversely, disruption of the primary cilium affects cell polarization (26,27). To assess whether the distortion of the primary cilium in response to activation of lipogenesis is accompanied by changes in epithelial cell polarization, MDCK cells were plated on a solid substratum and infected with the nSREBP1c-encoding adenovirus or empty control virus.…”