TNF-alpha promotes cilia elongation via mixed lineage kinases signaling in mouse fibroblasts and human RPE-1 cells

The primary cilium is a characteristic feature of most non-immune cells and functions as an environmental signal transduction sensor. The defects in primary cilium have profound effects on the developmental program, including the maturation of retinal epithelium. The ciliary length is tightly regulated during ciliogenesis, but the impact of inflammation on ciliary length remains elusive. The current study investigates the outcome of inflammatory stimuli for the primary cilium length in retinal epithelium cells and mouse embryonic fibroblasts. Here, we report that exposure to the pro-inflammatory cytokine TNF-alpha elongates cilia in a mixed-lineage kinase (MLK)-dependent manner. Pro-inflammatory stimuli such as bacterial LPS and interferon-gamma have similar effects on ciliary length. In contrast, febrile condition-mimicking heat stress dramatically reduced the number of ciliated cells regardless of TNF-alpha exposure but did not shorten TNF-induced elongation, suggesting distinct but rapid effects of inflammatory stresses on ciliogenesis.