EFFICIENT ASSOCIATION OF AN AMINO-TERMINALLY EXTENDED FORM OF HUMAN LATENT TRANSFORMING GROWTH-FACTOR-BETA BINDING-PROTEIN WITH THE EXTRACELLULAR-MATRIX

Latent transforming growth factor-beta (TGF-beta) binding protein-1 (L TBP-1) is a component of the high molecular weight latent TGF-beta com plex found in various cells, including human platelets, LTBP-1 is obse rved as different molecular sizes in different cell types, probably du e to proteolytic processing and alternative splicing. We here report a novel form of human LTBP-1, which is longer in its NH2-terminal part (LTBP-1L), Northern hybridization analysis revealed that the LTBP-1L i s derived from a 7.0 kilobase mRNA, whereas the originally reported sh orter form (LTBP-1S) is derived from a 5.2-kilobase mRNA, Transfection of cDNA for LTBP-1L and -1S in COS cells revealed that LTBP-1L bound more efficiently to the extracellular matrix than did LTBP-1S. These r esults suggest that the different splice forms of LTBP-1 mediate diffe rent localization patterns of the latent TGF-beta complexes in vivo.