Primary Cilium-Mediated Crosstalk of Signaling Cascades in Ciliogenesis: Implications for Tumorigenesis and Senescence

Primary cilium, a small, antenna-like, microtubule (MT)-based extracellular organelle, which extends from the surface of all types of human cells, has important roles in various cellular functions, including planar cell polarity, cell growth, cell cycle, cell migration, transactivation, and immune response. Primary cilium-mediated signaling cascades are initiated by chemosensing environmental signals, such as growth factors and morphogens that activate ciliary receptor-mediated signal transduction, or by mechanosensing of fluid flow followed by induction of intracellular Ca²⁺ flux. Owing to the versatile tools that cilia have, enabling various cellular functions, ciliary dysfunction causes several cilium-related human disorders such as ciliopathies. Here, we focus on the structure and biogenesis of primary cilium and discuss primary cilium-mediated crosstalk of the molecular mechanisms of signaling cascades in ciliogenesis, tumorigenesis, and senescence.