TNF-alpha promotes cilia elongation via Mixed Lineage Kinases signaling

The primary cilium is characteristic of most of non-immune cells and acts as an environmental signal transduction sensor. The defects in primary cilium have profound consequences on the developmental program, including the maturation of retinal epithelium. The ciliary length is tightly regulated during ciliogenesis. Additionally, many features of ciliogenesis are shared with an immune synapse formation. While the interaction between the cells within an immune synapse is well-characterized, the impact of inflammatory stresses on ciliogenesis in non-immune cells remains elusive. The current study investigates the outcome of inflammatory stimuli for the primary cilium in human retinal epithelial cells. Here, we report that the exposure of retinal epithelium cells to pro-inflammatory cytokine TNF-alpha elongates cilia in a Mixed-Lineage Kinase (MLK) - dependent manner. In contrast, febrile condition-mimicking heat stress dramatically reduced the number of ciliated cells regardless of TNF-alpha exposure, suggesting distinct but rapid effects of inflammatory stresses on ciliogenesis.