Human transforming growth factor alpha (TGF-alpha) is digested to a smaller (1-43), less biologically active, form in acidic gastric juice

Acquisition of cell motility is often correlated with the malignant progression of a transformed cell. To investigate some of the mechanisms involved in the development of a migratory state, we transfected the NBTII rat carcinoma cell line, which forms stationary epithelial clusters in culture, with the gene encoding human transforming growth factor alpha (TGF alpha). Expression of TGF alpha in NBTII cells resulted in cells of motile and vimentin-positive phenotype with internalized desmosomal components, analogous to the treatment of cells with exogenous TGF alpha. The clones expressed a 5.2-kb TGF alpha message and synthesized an 18-kDa form of TGF alpha. Supernatants of TGF alpha-producing clones induced the internalization of desmosomal components, the production of vimentin, and increased motility in untransfected epithelial NBTII cells, indicating that the factor produced by the clones was in a biologically active form. TGF alpha-producing clones secreted significant levels of a 95-kDa gelatinolytic metal-loproteinase, virtually absent in untransfected cell supernatants. In contrast, levels of inhibitors of metalloproteinases and of a plasminogen activator were similar in untransfected and TGF alpha-transfected NBTII cells. These results suggest that expression of TGF alpha in an epithelial tumor cell results in the development of a motile, fibroblast-like phenotype with matrix-degrading potential, which could result in a more aggressive tumor in vivo.

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Transforming growth factor alpha: mutation of aspartic acid 47 and leucine 48 results in different biological activities.

Molecular and Cellular Biology ◽

10.1128/mcb.8.3.1247 ◽

1988 ◽

Vol 8 (3) ◽

pp. 1247-1252 ◽

Cited By ~ 35

Author(s):

E Lazar ◽

S Watanabe ◽

S Dalton ◽

M B Sporn

Keyword(s):

Amino Acids ◽

Biological Activity ◽

Amino Acid ◽

Growth Factor ◽

Aspartic Acid ◽

Transforming Growth Factor ◽

Biologically Active ◽

Single Amino Acid ◽

Transforming Growth Factor Alpha ◽

Factor Alpha

To study the relationship between the primary structure of transforming growth factor alpha (TGF-alpha) and some of its functional properties (competition with epidermal growth factor (EGF) for binding to the EGF receptor and induction of anchorage-independent growth), we introduced single amino acid mutations into the sequence for the fully processed, 50-amino-acid human TGF-alpha. The wild-type and mutant proteins were expressed in a vector by using a yeast alpha mating pheromone promoter. Mutations of two amino acids that are conserved in the family of the EGF-like peptides and are located in the carboxy-terminal part of TGF-alpha resulted in different biological effects. When aspartic acid 47 was mutated to alanine or asparagine, biological activity was retained; in contrast, substitutions of this residue with serine or glutamic acid generated mutants with reduced binding and colony-forming capacities. When leucine 48 was mutated to alanine, a complete loss of binding and colony-forming abilities resulted; mutation of leucine 48 to isoleucine or methionine resulted in very low activities. Our data suggest that these two adjacent conserved amino acids in positions 47 and 48 play different roles in defining the structure and/or biological activity of TGF-alpha and that the carboxy terminus of TGF-alpha is involved in interactions with cellular TGF-alpha receptors. The side chain of leucine 48 appears to be crucial either indirectly in determining the biologically active conformation of TGF-alpha or directly in the molecular recognition of TGF-alpha by its receptor.

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Synthesis of biologically active transforming growth factor alpha

International journal of peptide & protein research ◽

10.1111/j.1399-3011.1987.tb02269.x ◽

2009 ◽

Vol 29 (3) ◽

pp. 421-431 ◽

Cited By ~ 41

Author(s):

JAMES P. TAM

Keyword(s):

Growth Factor ◽

Transforming Growth Factor ◽

Biologically Active ◽

Transforming Growth Factor Alpha ◽

Factor Alpha

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Transforming growth factor alpha: mutation of aspartic acid 47 and leucine 48 results in different biological activities

Molecular and Cellular Biology ◽

10.1128/mcb.8.3.1247-1252.1988 ◽

1988 ◽

Vol 8 (3) ◽

pp. 1247-1252

Author(s):

E Lazar ◽

S Watanabe ◽

S Dalton ◽

M B Sporn

Keyword(s):

Amino Acids ◽

Biological Activity ◽

Amino Acid ◽

Growth Factor ◽

Aspartic Acid ◽

Transforming Growth Factor ◽

Biologically Active ◽

Single Amino Acid ◽

Transforming Growth Factor Alpha ◽

Factor Alpha

To study the relationship between the primary structure of transforming growth factor alpha (TGF-alpha) and some of its functional properties (competition with epidermal growth factor (EGF) for binding to the EGF receptor and induction of anchorage-independent growth), we introduced single amino acid mutations into the sequence for the fully processed, 50-amino-acid human TGF-alpha. The wild-type and mutant proteins were expressed in a vector by using a yeast alpha mating pheromone promoter. Mutations of two amino acids that are conserved in the family of the EGF-like peptides and are located in the carboxy-terminal part of TGF-alpha resulted in different biological effects. When aspartic acid 47 was mutated to alanine or asparagine, biological activity was retained; in contrast, substitutions of this residue with serine or glutamic acid generated mutants with reduced binding and colony-forming capacities. When leucine 48 was mutated to alanine, a complete loss of binding and colony-forming abilities resulted; mutation of leucine 48 to isoleucine or methionine resulted in very low activities. Our data suggest that these two adjacent conserved amino acids in positions 47 and 48 play different roles in defining the structure and/or biological activity of TGF-alpha and that the carboxy terminus of TGF-alpha is involved in interactions with cellular TGF-alpha receptors. The side chain of leucine 48 appears to be crucial either indirectly in determining the biologically active conformation of TGF-alpha or directly in the molecular recognition of TGF-alpha by its receptor.

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MOLECULAR CONTROL OF ARTICULAR CARTILAGE DEGENERATION BY TRANSFORMING GROWTH FACTOR ALPHA

Clinical & Investigative Medicine ◽

10.25011/cim.v31i4.4787 ◽

2008 ◽

Vol 31 (4) ◽

pp. 2

Author(s):

Tom Appleton ◽

Shirine Usmani ◽

John Mort ◽

Frank Beier

Keyword(s):

Gene Expression ◽

Articular Cartilage ◽

Growth Factor ◽

P38 Mapk ◽

Transforming Growth Factor ◽

Cartilage Degeneration ◽

Signalling Pathways ◽

Transforming Growth Factor Alpha ◽

Factor Alpha ◽

Articular Cartilage Degeneration

Background: Articular cartilage degeneration is a hallmark of osteoarthritis (OA). We previously identified increased expression of transforming growth factor alpha (TGF?) and chemokine (C-C motif) ligand 2 (CCL2) in articular cartilage from a rat modelof OA (1,2). We subsequently reported that TGF? signalling modified chondrocyte cytoskeletal organization, increased catabolic and decreased anabolic gene expression and suppressed Sox9. Due to other roles in chondrocytes, we hypothesized that the effects ofTGF? on chondrocytes are mediated by Rho/ROCK and MEK/ERK signaling pathways. Methods: Primary cultures of chondrocytes and articularosteochondral explants were treated with pharmacological inhibitors of MEK1/2(U0126), ROCK (Y27632), Rho (C3), p38 MAPK (SB202190) and PI3K (LY294002) to elucidate pathway involvement. Results: Using G-LISA we determined that stimulation of primary chondrocytes with TGF? activates RhoA. Reciprocally, inhibition of RhoA/ROCK but not other signalling pathways prevents modification of the actin cytoskeleton in responseto TGF?. Inhibition of MEK/ERKsignaling rescued suppression of anabolic gene expression by TGF? including SOX9 mRNA and protein levels. Inhibition of MEK/ERK, Rho/ROCK, p38 MAPK and PI3K signalling pathways differentially controlled the induction of MMP13 and TNF? gene expression. TGF? also induced expression of CCL2 specifically through MEK/ERK activation. In turn, CCL2 treatment induced the expression of MMP3 and TNF?. Finally, we assessed cartilage degradation by immunohistochemical detection of type II collagen cleavage fragments generated by MMPs. Blockade of RhoA/ROCK and MEK/ERK signalling pathways reduced the generation of type IIcollagen cleavage fragments in response to TGF? stimulation. Conclusions: Rho/ROCK signalling mediates TGF?-induced changes inchondrocyte morphology, while MEK/ERK signalling mediates the suppression ofSox9 and its target genes, and CCL2 expression. CCL2, in turn, induces the expression of MMP3 and TNF?, two potent catabolic factors known to be involved in OA. These pathways may represent strategic targets for interventional approaches to treating cartilage degeneration in osteoarthritis. References: 1. Appleton CTG et al. Arthritis Rheum 2007;56:1854-68. 2. Appleton CTG et al. Arthritis Rheum 2007; 56:3693-705.

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