Molecular and functional aspects of latent transforming growth factor-beta binding protein: just a masking protein?

Latent transforming growth factor-beta (TGFbeta) binding protein (LTBP), a component of the high-molecular-weight latent TGFbeta complex, is found in various cell and tissue types. Originally described as a TGFbeta-masking protein, recent detections of four isoforms and numerous splice variants provide new aspects of its putative functional role. Regulation and sequestration of TGFbeta activity and structural remodeling of the extracellular matrix (ECM) seem to be the main tasks, but other possible functions might exist. The mechanism by which LTBP interacts with cell surface molecules or cellular receptors and ECM components remains unclear. Cellular, molecular and functional aspects will be discussed.