Transforming growth factor beta (TGF-β) was also shown to activate the PI3K-Akt-mTOR pathway in lung myofibroblasts which in turn activates activating transcription factor 4 (ATF4) driving increased expression of the serine-glycine synthesis pathway enzymes that result in excessive deposition of collagen proteins and scarring in idiopathic pulmonary fibrosis. This evidence concerns the gene ATF4 and pulmonary fibrosis.