DETERMINATION OF TYPE-I RECEPTOR SPECIFICITY BY THE TYPE-II RECEPTORSFOR TGF-BETA OR ACTIVIN

Transforming growth factor-beta (TGF-beta) and activin signal primaril y through interaction with type I and type II receptors, which are tra nsmembrane serine-threonine kinases. Tsk 7L is a type I receptor for T GF-beta and requires coexpression of the type II TGF-beta receptor for ligand binding. Tsk 7L also specifically bound activin, when coexpres sed with the type IIA activin receptor. Tsk 7L could associate with ei ther type II receptor and the ligand binding specificity of Tsk 7L was conferred by the type II receptor. Tsk 7L can therefore act as type I receptor for both activin and TGF-beta, and possibly other ligands.