Fibrillin controls TGF-β activation

Secreted transforming growth factor-βs (TGF-βs) are rendered biologically inactive by binding proteins that also target and concentrate them to the extracellular matrix. Specific, but still poorly understood, activation is required for disassembly of the extracellular matrix–bound protein complex to liberate the mature growth factor and to obtain a correct biological effect. A new study shows that fibrillin-1, the protein defective in Marfan syndrome, has a biologically important role in controlling TGF-β activation in the lung.