Hsp90α forms a stable complex at cilia neck for signal molecules interaction in cilia-mediated IGF-1 receptor signaling

Abstract

Primary cilium is composed of an axoneme protruded on cell surface, a basal body beneath the membrane and a transition neck in between. It is considered as a sensory organelle on plasma membrane to mediate extracellular signals. The transition neck region contains the microtubules from triplet to doublet transition, the transition fibres crosslinking the axoneme with membrane and the necklace proteins regulating molecules being transported into and out of cilium. In this protein-enriched complex area it is important to maintain all these proteins in proper assembly. Here, through immunofluorescence staining and protein isolation, we identified that the molecular chaperone, Hsp90α, clustered at periciliary base. At transition neck region the phosphorylated Hsp90α formed a stable ring around axoneme. Heat shock treatment dissipated Hsp90α and induced cilia resorption. We further identified that Hsp90α at transition neck region represented a signalling platform on which IRS-1 interacted with intracellular downstream signal molecules for IGF-1 receptor signalling.