Receptor. 1993 : Mathews LS, Vale WW. Related Articles, Links Molecular and functional characterization of activin receptors.

Sakuma et al. 2002: The signalling pathway of Nodal was investigated with the use of a Nodal-responsive assay system based on frog animal caps. Expression of dominant negative mutants of various receptors indicated that ALK4, and either ActRIIA or ActRIIB, function as type I and type II receptors for Nodal, respectively. A soluble form of Cripto lacking the COOH-terminal region interacted with Nodal but failed to mediate Nodal signalling, indicating that the native Cripto protein functions as a membrane-bound co-receptor for Nodal. Processed forms of Lefty proteins, both smaller and larger forms, inhibited Nodal signalling. Such Lefty-induced inhibition was rescued by excess ActRIIA or ActRIIB, suggesting that Lefty antagonizes Nodal signalling through competitive binding to the common receptor ActRIIA or ActRIIB. This idea was supported by the demonstration of a genetic interaction between lefty2 and ActRIIB in mouse. Behaviours of GFP-Nodal and GFP-Lefty2 proteins were also investigated in chick embryos. Both proteins could diffuse over a long distance, but the latter diffused faster than the former.

Truncated activin type II receptors inhibit bioactivity by the formation of heteromeric complexes with activin type I. receptors. Exp Cell Res. 1996

Activin type IIA and IIB receptors mediate Gdf11 signaling in axial vertebral patterning.GDF11 binds to both ActRIIA and ActRIIB, and induces phosphorylation of Smad2. It is interesting to note that activin type IIA was only weakly coprecipitated with ALK4 in the absence of Gdf11, whereas IIB was coprecipitated with ALK4 regardless of Gdf11, suggesting a different binding property of IIA and IIB to ALK4 (Oh et al 2002).

Activin type IIA and IIB receptors mediate Gdf11 signaling in axial vertebral patterning.GDF11 binds to both ActRIIA and ActRIIB, and induces phosphorylation of Smad2. It is interesting to note that activin type IIA was only weakly coprecipitated with ALK4 in the absence of Gdf11, whereas IIB was coprecipitated with ALK4 regardless of Gdf11, suggesting a different binding property of IIA and IIB to ALK4 (Oh et al 2002).