Activation of the Gi protein-RHOA axis by non-canonical Hedgehog signaling is independent of primary cilia.

08:00 EDT 27th August 2018 | BioPortfolio

Summary of "Activation of the Gi protein-RHOA axis by non-canonical Hedgehog signaling is independent of primary cilia."

Primary cilia are solitary organelles that emanate from the plasma membrane during growth arrest in almost all mammalian cells. The canonical Hedgehog (HH) pathway requires trafficking of the G protein-coupled receptor SMOOTHENED (SMO) and the GLI transcription factors to the primary cilium upon binding of a HH ligand to PATCHED1. However, it is unknown if activation of the small GTPase RHOA by SMO coupling to heterotrimeric Gi proteins, a form of non-canonical HH signaling, requires localization of SMO in the primary cilium. In this study, we compared RHOA and Gi protein stimulation by activation of SMO or sphingosine 1-phosphate receptor (S1P) receptors in WT and KIF3A-deficient mouse embryonic fibroblasts that lack primary cilia. We found that activation of SMO in response to Sonic HH (SHH) or purmorphamine (PUR), a small molecule agonist of SMO, stimulates Gi proteins and RHOA independently of the presence of primary cilia, similar to the effects of S1P. However, while S1P induced a fast activation of AKT that is sensitive to the Gi inhibitor pertussis toxin, HH pathway activators did not significantly activate AKT, suggesting that RHOA activation is not downstream of AKT. Our findings demonstrate that early events in some forms of non-canonical HH signaling occur in extraciliary membranes, which might be particularly relevant for actively-cycling cells, for some cancers characterized by loss of primary cilia, and in ciliopathies.


Journal Details

This article was published in the following journal.

Name: PloS one
ISSN: 1932-6203
Pages: e0203170


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Medical and Biotech [MESH] Definitions

A frizzled-like, G-protein-coupled receptor that associates with PATCHED RECEPTORS to transduce signals from HEDGEHOG PROTEINS and initiate hedgehog signaling to ZINC FINGER PROTEIN GLI1. It may normally inhibit signaling in the absence of SONIC HEDGEHOG PROTEIN binding to PATCHED RECEPTOR-1.

A patched receptor for several HEDGEHOG PROTEINS that associates with the SMOOTHENED RECEPTOR to modulate hedgehog signaling. It is also a TUMOR SUPPRESSOR PROTEIN; mutations in the patched-1 gene are associated with BASAL CELL NEVUS SYNDROME; SQUAMOUS CELL CARCNIOMA of the ESOPHAGUS; trichoepitheliomas, and CARCINOMA, TRANSITIONAL CELL of the URINARY BLADDER.

A family of intercellular signaling proteins that play and important role in regulating the development of many TISSUES and organs. Their name derives from the observation of a hedgehog-like appearance in DROSOPHILA embryos with genetic mutations that block their action.

A NOD signaling adaptor protein that contains two C-terminal leucine-rich domains which recognize bacterial PEPTIDOGLYCAN. It signals via an N-terminal capase recruitment domain that interacts with other CARD SIGNALING ADAPTOR PROTEINS such as RIP SERINE-THEONINE KINASES. The protein plays a role in the host defense response by signaling the activation of CASPASES and the MAP KINASE SIGNALING SYSTEM. Mutations of the gene encoding the nucleotide oligomerization domain 2 protein have been associated with increased susceptibility to CROHN DISEASE.

A Wnt protein and ligand for FRIZZLED RECEPTORS that may function as an inhibitor or activator of the WNT SIGNALING PATHWAY. For example, it activates signaling in the presence of Frizzled-4 but is inhibitory when coupled with ROR2 TYROSINE KINASE. It is required for axis formation during EMBRYOGENESIS and inhibits the proliferation, migration, and invasiveness of cancer cells.

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