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Interaction of smoothened with integrin-linked kinase in primary cilia mediates Hedgehog signalling.

ABSTRACT: Here we report that ILK localizes in the mouse primary cilium, a sensory organelle required for signalling by the Hedgehog (Hh) pathway. Genetic or pharmacological inhibition of ILK blocks ciliary accumulation of the Hh pathway effector smoothened (Smo) and suppresses the induction of Gli transcription factor mRNAs by SHh. Conditional deletion of ILK or Smo also inhibits SHh-driven activation of Gli2 in the embryonic mouse cerebellum. ILK regulation of Hh signalling probably requires the physical interaction of ILK and Smo in the cilium, and we also show selective cilia-associated interaction of ILK with ?-arrestin, a known mediator of Smo-dependent signalling.

SUBMITTER: Barakat B

PROVIDER: S-EPMC3790053 | biostudies-literature | 2013 Sep

REPOSITORIES: biostudies-literature

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Interaction of smoothened with integrin-linked kinase in primary cilia mediates Hedgehog signalling.

Barakat Badia B Yu Liang L Lo Camden C Vu Duc D De Luca Elisabetta E Cain Jason E JE Martelotto Luciano G LG Dedhar Shoukat S Sadler Anthony J AJ Wang Die D Watkins D Neil DN Hannigan Gregory E GE

EMBO reports 20130723 9

Here we report that ILK localizes in the mouse primary cilium, a sensory organelle required for signalling by the Hedgehog (Hh) pathway. Genetic or pharmacological inhibition of ILK blocks ciliary accumulation of the Hh pathway effector smoothened (Smo) and suppresses the induction of Gli transcription factor mRNAs by SHh. Conditional deletion of ILK or Smo also inhibits SHh-driven activation of Gli2 in the embryonic mouse cerebellum. ILK regulation of Hh signalling probably requires the physica ...[more]

PMID: 23877428

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A Smoothened-Evc2 complex transduces the Hedgehog signal at primary cilia.

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Ankmy2 Prevents Smoothened-Independent Hyperactivation of the Hedgehog Pathway via Cilia-Regulated Adenylyl Cyclase Signaling.

Project description:The mechanisms underlying subcellular targeting of cAMP-generating adenylyl cyclases and processes regulated by their compartmentalization are poorly understood. Here, we identify Ankmy2 as a repressor of the Hedgehog pathway via adenylyl cyclase targeting. Ankmy2 binds to multiple adenylyl cyclases, determining their maturation and trafficking to primary cilia. Mice lacking Ankmy2 are mid-embryonic lethal. Knockout embryos have increased Hedgehog signaling and completely open neural tubes showing co-expansion of all ventral neuroprogenitor markers, comparable to the loss of the Hedgehog receptor Patched1. Ventralization in Ankmy2 knockout is completely independent of the Hedgehog pathway transducer Smoothened. Instead, ventralization results from the reduced formation of Gli2 and Gli3 repressors and early depletion of adenylyl cyclase III in neuroepithelial cilia, implicating deficient pathway repression. Ventralization in Ankmy2 knockout requires both cilia and Gli2 activation. These findings indicate that cilia-dependent adenylyl cyclase signaling represses the Hedgehog pathway and promotes morphogenetic patterning.

| S-EPMC9042708 | biostudies-literature

Primary cilia disassembly down-regulates mechanosensitive hedgehog signalling: a feedback mechanism controlling ADAMTS-5 expression in chondrocytes.

Project description:ObjectiveHedgehog signalling is mediated by the primary cilium and promotes cartilage degeneration in osteoarthritis. Primary cilia are influenced by pathological stimuli and cilia length and prevalence are increased in osteoarthritic cartilage. This study aims to investigate the relationship between mechanical loading, hedgehog signalling and cilia disassembly in articular chondrocytes.MethodsPrimary bovine articular chondrocytes were subjected to cyclic tensile strain (CTS; 0.33 Hz, 10% or 20% strain). Hedgehog pathway activation (Ptch1, Gli1) and A Disintegrin And Metalloproteinase with Thrombospondin Motifs 5 (ADAMTS-5) expression were assessed by real-time PCR. A chondrocyte cell line generated from the Tg737(ORPK) mouse was used to investigate the role of the cilium in this response. Cilia length and prevalence were quantified by immunocytochemistry and confocal microscopy.ResultsMechanical strain upregulates Indian hedgehog expression and activates hedgehog signalling. Ptch1, Gli1 and ADAMTS-5 expression were increased following 10% CTS, but not 20% CTS. Pathway activation requires a functioning primary cilium and is not observed in Tg737(ORPK) cells lacking cilia. Mechanical loading significantly reduced cilium length such that cilia became progressively shorter with increasing strain magnitude. Inhibition of histone deacetylase 6 (HDAC6), a tubulin deacetylase, prevented cilia disassembly and restored mechanosensitive hedgehog signalling and ADAMTS-5 expression at 20% CTS.ConclusionsThis study demonstrates for the first time that mechanical loading activates primary cilia-mediated hedgehog signalling and ADAMTS-5 expression in adult articular chondrocytes, but that this response is lost at high strains due to HDAC6-mediated cilia disassembly. The study provides new mechanistic insight into the role of primary cilia and mechanical loading in articular cartilage.

| S-EPMC3988976 | biostudies-literature

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