Expression and dimerization of the rat activin subunits βC and βE: Evidence for the formation of novel activin dimers

Abstract

Activins are cytokines of the transforming growth factor β family, which plays a central role in the determination of cell fate and the regulation of tissue balance. Family members are composed of two subunits and this dimerization is critical for liganding their cognate receptors and execution of proper functions. In the current study we focused on the localization of activin βA, βB, βC and βE subunits in the adult rat and analyzed the composition of putative activin β dimers. By dissecting tissue distribution of various activins we found that the liver, in particular the hepatocytes, is the major source for activin βC and βE transcripts, since other tissues almost failed to express these isoforms. In sharp contrast, the emergence of activin βA and βB appeared ubiquitous. Using a highly selective proteome approach, we were able to identify homo- as well as heterodimers of individual activin subunits, indicating a high redundancy of ligand composition. Certainly, this broad potential to homo- and heterodimerize has to be considered in future studies on activin function.