Latent transforming growth factor-beta complex in Chinese hamster ovary cells contains the multifunctional cysteine-rich fibroblast growth factor receptor, also termed E-selectin-ligand or MG-160.
Transforming growth factor-beta (TGF-beta) is secreted as latent high molecular mass complexes from producer cells. The N-terminal precursor remnant, also called latency-associated peptide (LAP), forms a non-covalently linked complex with TGF-beta and confers the latency to TGF-beta. In human platelets and certain other cell types, latent TGF-beta binding protein-1 (LTBP-1) is disulphide-linked to LAP, and forms complexes of more than 230 kDa. In addition, LTBP-2 and -3, which are structurally similar to LTBP-1, can be part of latent TGF-beta complexes. In Chinese hamster ovary (CHO) cells transfected with the TGF-beta1 cDNA, a major part of the latent TGF-beta secreted into the medium is a 100-kDa small latent complex containing TGF-beta and LAP. In addition, we found two other forms of latent TGF-beta complexes, i.e. a 220-kDa complex containing LTBP-1, and a 220-kDa complex containing a 140-kDa protein. Purification of the 140-kDa component, termed latent TGF-beta complexed protein-1 (LTCP-1), followed by amino acid sequencing and cDNA cloning from a CHO cell cDNA library, revealed that it is a hamster counterpart of a previously identified, multifunctional protein known as chicken cysteine-rich fibroblast growth factor (FGF) receptor, mouse E-selectin-ligand and rat MG-160 (a 160-kDa membrane sialoglycoprotein of the Golgi apparatus). Immunoprecipitation of LTCP-1 and TGF-beta1 from CHO cells stably transfected with TGF-beta1 precursor cDNA revealed that the expressed protein forms a complex with LAP, and that a major part of the complex is secreted. Northern blot analysis showed that mRNA for LTCP-1 was expressed in large amounts in testis, ovary and placenta, but less abundantly in other tissues. These results suggest that TGF-beta, produced in certain cell types, may form a complex with LTCP-1, which may have different properties compared with other latent TGF-beta complexes. It remains to be investigated whether the complex formation between LTCP-1 and TGF-beta1 also occurs in other cells, whether the association between them occurs in the Golgi complex, and whether it affects the interaction of LTCP-1 with FGF or E-selectin.
Olofsson
A
A
Ludwig Institute for Cancer Research, Box 595, Biomedical Center, S-751 24 Uppsala, Sweden.
Hellman
U
U
Ten Dijke
P
P
Grimsby
S
S
Ichijo
H
H
Morén
A
A
Miyazono
K
K
Heldin
C H
CH
D000328:Adult; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D016466:CHO Cells; D002352:Carrier Proteins / Q000378:metabolism; D002645:Chickens; D006224:Cricetinae; D003412:Cricetulus / Q000235:genetics*; D017077:Culture Media, Conditioned / Q000737:chemistry; D018076:DNA, Complementary / Q000235:genetics; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D053779:Latent TGF-beta Binding Proteins; D046911:Macromolecular Substances; D008562:Membrane Glycoproteins / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D009928:Organ Specificity; D010446:Peptide Fragments; D011498:Protein Precursors; D011506:Proteins / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D011956:Receptors, Cell Surface; D017468:Receptors, Fibroblast Growth Factor / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D012795:Sialoglycoproteins / Q000302:isolation & purification / Q000378:metabolism*; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000378:metabolism*; D053773:Transforming Growth Factor beta1
D002352:Carrier Proteins; D017077:Culture Media, Conditioned; D018076:DNA, Complementary; D047908:Intracellular Signaling Peptides and Proteins; C509032:LTBP1 protein, human; C509035:LTBP2 protein, human; D053779:Latent TGF-beta Binding Proteins; C509033:Ltbp1 protein, mouse; C509036:Ltbp2 protein, mouse; C509037:Ltbp2 protein, rat; D046911:Macromolecular Substances; D008562:Membrane Glycoproteins; D010446:Peptide Fragments; D011498:Protein Precursors; D011506:Proteins; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D017468:Receptors, Fibroblast Growth Factor; D011993:Recombinant Fusion Proteins; D012795:Sialoglycoproteins; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; C086711:cysteine-rich fibroblast growth factor receptor