Latent Transforming Growth Factor Beta Binding Protein 4 (LTBP4)

Transforming growth factor-beta, or TGFB, remains biologically latent after secretion, blocked from activity by its N-terminal propeptide (the latency-associated peptide, or LAP). TGFB is activated by its dissociation from LAP. The latent form of TGFB is secreted in association with a latent TGFB-binding protein, or LTBP (see LTBP1), and assembled into the extracellular matrix. LTBPs are mainly composed of epidermal growth factor (EGF)-like repeats and protein domains with 8-cysteine repeats, both of which are also found in fibrillins. Northern blot analysis detected strong expression of an approximately 5-kb LTBP4 transcript in heart, with slightly lower expression in skeletal muscle and pancreas, moderate expression in placenta and lung, and weak or no expression in brain, liver, and kidney.