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

Latent transforming growth factor-beta (TGF beta) binding protein (LTBP), a component of the high-molecular-weight latent TGF beta complex, is found i n various cell and tissue types. Originally described as a TGF beta-masking protein, recent detections of four isoforms and numerous splice variants p rovide new aspects of its putative functional role. Regulation and sequestr ation of TGF beta activity and structural remodeling of the extracellular m atrix (ECM) seem to be the main tasks, but other possible functions might e xist. 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.