Functional characterization of a unique mutant of ALK2, p.K400E, that is associated with a skeletal disorder, diffuse idiopathic skeletal hyperostosis

• Published in: Bone (New York, N.Y.) N.Y.), 2020-08, Vol.137, p.115410-115410, Article 115410
• Main Authors: Tsukamoto, Sho, Kuratani, Mai, Katagiri, Takenobu
• Format: Article
• Language: English
• Subjects: Activin receptor-like kinase 2 (ALK2); Activin Receptors, Type I - genetics; Activin Receptors, Type I - metabolism; BMP signaling; Bone Morphogenetic Proteins - metabolism; Diffuse idiopathic skeletal hyperostosis; Humans; Hyperostosis, Diffuse Idiopathic Skeletal - genetics; Myositis Ossificans - genetics; Phosphorylation; Signal Transduction; Skeletal disorder
• ISSN: 8756-3282; 1873-2763
• DOI: 10.1016/j.bone.2020.115410

Bone morphogenetic protein (BMP) signaling regulates the physiological and pathological development of skeletal tissues. Activin receptor-like kinase 2 (ALK2) is a BMP type I transmembrane serine/threonine kinase receptor. Recently, a p.K400E mutation was found in ALK2 in a patient with diffuse idiopathic skeletal hyperostosis (DISH), which is a disorder characterized by calcification and ossification of spinal ligaments and entheses. We report here the functional characterization of ALK2 p.K400E in vitro. Cells overexpressing ALK2 p.K400E activated BMP signaling in response to osteogenic BMP ligands. However, ALK2 p.K400E was not activated by a nonosteogenic ligand, Activin A. BMP signaling through ALK2 p.K400E was further enhanced by the coexpression of a BMP type II receptor. The type II receptor increased the phosphorylation level of ALK2 p.K400E, suggesting that ALK2 p.K400E is a hypersensitive mutant to the BMP type II receptor kinases. Our findings suggest that pathological calcification and ossification in DISH are caused by overactivated BMP signaling through ALK2 p.K400E enhanced by type II receptors in response to osteogenic BMPs rather than Activin A. •Activin receptor-like kinase 2 (ALK2) is a transmembrane kinase receptor for bone morphogenetic proteins (BMPs).•Diffuse idiopathic skeletal hyperostosis (DISH) is characterized by calcification and ossification of ligaments and enthesis.•A p.K400E mutation was found in ALK2 in a patient with DISH.•ALK2 p.K400E was activated by osteogenic BMPs, but not Activin A, and enhanced by the coexpression of a BMP type II receptor.