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Pathogenic ACVR1R206H activation by Activin A-induced receptor clustering and autophosphorylation

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journal contribution
posted on 21.07.2021, 13:31 by Anassuya Ramachandran, Merima Mehić, Laabiah Wasim, Dessislava Malinova, Ilaria Gori, Beata K Blaszczyk, Diana M Carvalho, Eileen M Shore, Chris Jones, Marko Hyvönen, Pavel Tolar, Caroline S Hill
Fibrodysplasia ossificans progressiva (FOP) and diffuse intrinsic pontine glioma (DIPG) are debilitating diseases that share causal mutations in ACVR1, a TGF-β family type I receptor. ACVR1R206H is a frequent mutation in both diseases. Pathogenic signaling via the SMAD1/5 pathway is mediated by Activin A, but how the mutation triggers aberrant signaling is not known. We show that ACVR1 is essential for Activin A-mediated SMAD1/5 phosphorylation and is activated by two distinct mechanisms. Wild-type ACVR1 is activated by the Activin type I receptors, ACVR1B/C. In contrast, ACVR1R206H activation does not require upstream kinases, but is predominantly activated via Activin A-dependent receptor clustering, which induces its auto-activation. We use optogenetics and live-imaging approaches to demonstrate Activin A-induced receptor clustering and show it requires the type II receptors ACVR2A/B. Our data provide molecular mechanistic insight into the pathogenesis of FOP and DIPG by linking the causal activating genetic mutation to disrupted signaling.

Funding

Crick (Grant ID: 10095, Grant title: Hill FC001095) Crick (Grant ID: 10185, Grant title: Tolar FC001185)

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