Transforming growth factor-beta 1, -beta 2, and -beta 3 secreted by a human glioblastoma cell line. Identification of small and different forms of large latent complexes.
Transforming growth factor-beta 1 (TGF-beta 1) has been found to occur as latent high molecular weight complexes, with or without an associated component denoted latent TGF-beta 1-binding protein (LTBP). We show here that a human glioblastoma cell line (U-1240 MG) secretes all isoforms of TGF-beta s found in mammalian cells (TGF-beta 1, -beta 2, and -beta 3). Approximately 26% of the secreted TGF-beta is in an active form. Latent TGF-beta s were partially purified from medium conditioned by the U-1240 MG cell line using anion exchange chromatography. Analysis of the different fractions by immunoblotting using antisera against precursor parts of the different TGF-beta isoforms, and against LTBP, revealed that not only TGF-beta 1 but also other isoforms of TGF-beta may occur in high molecular weight forms containing LTBP. In addition, each one of the TGF-beta isoforms occurred in smaller forms not containing LTBP. Interestingly, each of the TGF-beta isoforms was also seen in complexes of about 210 kDa containing associated component(s) distinct from LTBP. These results indicate that each of the different isoforms of TGF-beta is synthesized and secreted by this glioblastoma cell line in several different high molecular weight latent forms; the biological importance of the various latent TGF-beta complexes is discussed.
Olofsson
A
A
Ludwig Institute for Cancer Research, Biomedical Center, Uppsala, Sweden.
Miyazono
K
K
Kanzaki
T
T
Colosetti
P
P
Engström
U
U
Heldin
C H
CH
D002352:Carrier Proteins / Q000378:metabolism*; D005910:Glioma / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D047908:Intracellular Signaling Peptides and Proteins; D053779:Latent TGF-beta Binding Proteins; D046911:Macromolecular Substances; D008970:Molecular Weight; D016212:Transforming Growth Factor beta / Q000145:classification / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; D053779:Latent TGF-beta Binding Proteins; D046911:Macromolecular Substances; D016212:Transforming Growth Factor beta