Regulation of activin's access to the cell: why is mother nature such a control freak?
Activin A is a pluripotent growth factor with important roles in development, erythropoiesis and the local regulation of many tissues. At the post-translational level, the amount of activin A produced by cells may be modulated through the diversion of activin A subunits into the formation of inhibin or other activins containing heterodimeric forms. Once assembled, activin interacts with various low- and high-affinity binding proteins, such as follistatin and alpha(2)-macroglobulin, that have consequences for receptor availability. In common with other TGFbeta family members, activin signals through pairs of type I and II receptor kinases and the Smad intracellular signalling cascade. Other checkpoints have been identified such as the recently identified pseudoreceptor, BAMBI. These emerging findings point to a tightly coordinated regulation of the exposure of a cell or tissue to activin, consistent with the low amounts of this potent factor that are necessary to modulate cellular responses.
Monash Institute of Reproduction & Development, Monash University, Clayton, Victoria 3168, Australia. david.phillips@monash.edu.au
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D029404:Activin Receptors; D028341:Activins; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism; D006133:Growth Substances / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D007265:Inhibins / Q000737:chemistry / Q000378:metabolism*; D008954:Models, Biological; D020836:Protein Structure, Quaternary; D017978:Receptors, Growth Factor / Q000378:metabolism; D015398:Signal Transduction
D002352:Carrier Proteins; D006133:Growth Substances; D017978:Receptors, Growth Factor; D028341:Activins; D007265:Inhibins; D029404:Activin Receptors