scholarly journals Cleavage of K-FGF produces a truncated molecule with increased biological activity and receptor binding affinity.

1993 ◽  
Vol 121 (3) ◽  
pp. 705-713 ◽  
Author(s):  
P Bellosta ◽  
D Talarico ◽  
D Rogers ◽  
C Basilico
Keyword(s):  
Amino Acids ◽  
Biological Activity ◽  
Growth Factor ◽  
Binding Affinity ◽  
Receptor Binding ◽  
Biologically Active ◽  
Heparin Binding ◽  
Wild Type ◽  
Mammalian Expression

The K-FGF/HST (FGF-4) growth factor is a member of the FGF family which is efficiently secreted and contains a single N-linked glycosylation signal. To study the role of glycosylation in the secretion of K-FGF, we mutated the human K-fgf cDNA to eliminate the glycosylation signal and the mutated cDNA was cloned into a mammalian expression vector. Studies of immunoprecipitation from the conditioned medium of cells expressing this plasmid revealed that the lack of glycosylation did not impair secretion, however the unglycosylated protein was immediately cleaved into two NH2-terminally truncated peptides of 13 and 15 kD, which appeared to be more biologically active than the wild-type protein. These two proteins also showed higher heparin binding affinity than that of wt K-FGF. We have expressed in bacteria the larger of these two proteins (K140), in which the NH2-terminal 36 amino acids present in the mature form of K-FGF have been deleted. Mitogenicity assays on several cell lines showed that purified recombinant K140 had approximately five times higher biological activity than wild-type recombinant K-FGF. Studies of receptor binding showed that K140 had higher affinity than wt K-FGF for two of the four members of FGF receptor's family, specifically for FGFR-1 (flg) and FGFR-2 (bek). K140 also had increased heparin binding ability, but this property does not appear to be responsible for the increased affinity for FGF receptors. Thus removal of the NH2-terminal 36 amino acids from the mature K-FGF produces growth factor molecules with an altered conformation, resulting in higher heparin affinity, and more efficient binding to FGF receptors. Although it is not clear whether cleavage of K-FGF to generate K140 occurs in vivo, this could represent a novel mechanism of modulation of growth factor activity.

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

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.

scholarly journals Structure-function analysis of human transforming growth factor-α by site-directed mutagenesis

1992 ◽  
Vol 283 (1) ◽  
pp. 91-98 ◽  
Author(s):  
J A Feild ◽  
R H Reid ◽  
D J Rieman ◽  
T P Kline ◽  
G Sathe ◽  
...  
Keyword(s):  
Biological Activity ◽  
Growth Factor ◽  
Receptor Binding ◽  
Transcriptional Control ◽  
Transforming Growth Factor ◽  
Function Analysis ◽  
Protein A ◽  
Site Directed Mutagenesis ◽  
Wild Type ◽  
Transforming Growth Factor Α

Site-directed mutants of transforming growth factor-alpha (TGF-alpha) were expressed in an Escherichia coli outer membrane protein A (ompA) expression/secretion vector under the transcriptional control of the lambda PL promoter. TGF-alpha mutant proteins were isolated from cell pellets using alkaline extraction with 0.1 M-Tris (pH 10.5). The levels of protein expression of 23 TGF-alpha mutants were comparable with those of wild-type TGF-alpha, as determined by immunoblotting and radioimmunoassay. An analysis of biological activity using as assays radioreceptor binding competition and colony formation in soft agar showed that the following mutations destroy the activity of TGF-alpha: Gly-19 to Val, Val-33 to Pro and Gly-40 to Val. Mutations of Arg-42 to Lys, Leu-48 to Ala, Tyr-38 to Trp or Phe-17 to Tyr significantly decrease, but do not destroy, biological activity when compared with the wild-type. Mutations in 14 other residues did not significantly alter receptor binding or colony-forming activity. These studies suggest that two domains localized at the surface of TGF-alpha are important in receptor binding and colony-forming activity. Domain I involves amino acid residues which include Tyr-38 and Leu-48; domain II includes residues Phe-15, Phe-17 and Arg-42.

scholarly journals Identification of nonessential disulfide bonds and altered conformations in the v-sis protein, a homolog of the B chain of platelet-derived growth factor.

1988 ◽  
Vol 8 (3) ◽  
pp. 1011-1018 ◽  
Author(s):  
M K Sauer ◽  
D J Donoghue
Keyword(s):  
Biological Activity ◽  
Growth Factor ◽  
Disulfide Bonds ◽  
Polyacrylamide Gel Electrophoresis ◽  
Protein A ◽  
Sodium Dodecyl ◽  
Biologically Active ◽  
Platelet Derived Growth Factor ◽  
Wild Type ◽  
Type V

The protein encoded by v-sis, the oncogene of simian sarcoma virus, is homologous to the B chain of platelet-derived growth factor (PDGF). There are eight conserved Cys residues between PDGF-B and the v-sis protein. Both native PDGF and the v-sis protein occur as disulfide-bonded dimers, probably containing both intramolecular and intermolecular disulfide bonds. Oligonucleotide-directed mutagenesis was used to change the Cys codons to Ser codons in the v-sis gene. Four single mutants lacked detectable biological activity, indicating that Cys-127, Cys-160, Cys-171, and Cys-208 are required for formation of a biologically active v-sis protein. The other four single mutants retained biological activity as determined in transformation assays, indicating that Cys-154, Cys-163, Cys-164, and Cys-210 are dispensable for biological activity. Double and triple mutants containing three of these altered sites were constructed, some of which were transforming as well. The v-sis proteins encoded by biologically active mutants displayed significantly reduced levels of dimeric protein compared with the wild-type v-sis protein, which dimerized very efficiently. Furthermore, a mutant with a termination codon at residue 209 exhibited partial transforming activity. This study thus suggests that the minimal region required for transformation consists of residues 127 to 208. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis indicated that the v-sis proteins encoded by some of the biologically active mutants exhibited an altered conformation when compared with the wild-type v-sis protein, and suggested that Cys-154 and Cys-163 participate in a nonessential disulfide bond.

Identification of nonessential disulfide bonds and altered conformations in the v-sis protein, a homolog of the B chain of platelet-derived growth factor

1988 ◽  
Vol 8 (3) ◽  
pp. 1011-1018
Author(s):  
M K Sauer ◽  
D J Donoghue
Keyword(s):  
Biological Activity ◽  
Growth Factor ◽  
Disulfide Bonds ◽  
Polyacrylamide Gel Electrophoresis ◽  
Protein A ◽  
Sodium Dodecyl ◽  
Biologically Active ◽  
Platelet Derived Growth Factor ◽  
Wild Type ◽  
Type V

The protein encoded by v-sis, the oncogene of simian sarcoma virus, is homologous to the B chain of platelet-derived growth factor (PDGF). There are eight conserved Cys residues between PDGF-B and the v-sis protein. Both native PDGF and the v-sis protein occur as disulfide-bonded dimers, probably containing both intramolecular and intermolecular disulfide bonds. Oligonucleotide-directed mutagenesis was used to change the Cys codons to Ser codons in the v-sis gene. Four single mutants lacked detectable biological activity, indicating that Cys-127, Cys-160, Cys-171, and Cys-208 are required for formation of a biologically active v-sis protein. The other four single mutants retained biological activity as determined in transformation assays, indicating that Cys-154, Cys-163, Cys-164, and Cys-210 are dispensable for biological activity. Double and triple mutants containing three of these altered sites were constructed, some of which were transforming as well. The v-sis proteins encoded by biologically active mutants displayed significantly reduced levels of dimeric protein compared with the wild-type v-sis protein, which dimerized very efficiently. Furthermore, a mutant with a termination codon at residue 209 exhibited partial transforming activity. This study thus suggests that the minimal region required for transformation consists of residues 127 to 208. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis indicated that the v-sis proteins encoded by some of the biologically active mutants exhibited an altered conformation when compared with the wild-type v-sis protein, and suggested that Cys-154 and Cys-163 participate in a nonessential disulfide bond.

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

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.

scholarly journals Vitamin D-Binding Protein Influences Total Circulating Levels of 1,25-Dihydroxyvitamin D3 but Does Not Directly Modulate the Bioactive Levels of the Hormone in Vivo

Endocrinology ◽  
2008 ◽  
Vol 149 (7) ◽  
pp. 3656-3667 ◽  
Author(s):  
Lee A. Zella ◽  
Nirupama K. Shevde ◽  
Bruce W. Hollis ◽  
Nancy E. Cooke ◽  
J. Wesley Pike
Keyword(s):  
Vitamin D ◽  
Biological Activity ◽  
Binding Protein ◽  
Biologically Active ◽  
Vitamin D Binding Protein ◽  
Wild Type ◽  
Dihydroxyvitamin D3 ◽  
Activation Profile

Mice deficient in the expression of vitamin D-binding protein (DBP) are normocalcemic despite undetectable levels of circulating 1,25-dihydroxyvitamin D3 [1,25(OH)2D3]. We used this in vivo mouse model together with cells in culture to explore the impact of DBP on the biological activity of 1,25(OH)2D3. Modest changes in the basal expression of genes involved in 1,25(OH)2D3 metabolism and calcium homeostasis were observed in vivo; however, these changes seemed unlikely to explain the normal calcium balance seen in DBP-null mice. Further investigation revealed that despite the reduced blood levels of 1,25(OH)2D3 in these mice, tissue concentrations were equivalent to those measured in wild-type counterparts. Thus, the presence of DBP has limited impact on the extracellular pool of 1,25(OH)2D3 that is biologically active and that accumulates within target tissues. In cell culture, in contrast, the biological activity of 1,25(OH)2D3 is significantly impacted by DBP. Here, although DBP deficiency had no effect on the activation profile itself, the absence of DBP strongly reduced the concentration of exogenous 1,25(OH)2D3 necessary for transactivation. Surprisingly, analogous studies in wild-type and DBP-null mice, wherein we explored the activity of exogenous 1,25(OH)2D3, produced strikingly different results as compared with those in vitro. Here, the carrier protein had virtually no impact on the distribution, uptake, activation profile, or biological potency of the hormone. Collectively, these experiments suggest that whereas DBP is important to total circulating 1,25(OH)2D3 and sequesters extracellular levels of this hormone both in vivo and in vitro, the binding protein does not influence the hormone’s biologically active pool.

Characterization and Optimization of Synthetic, VLDL Receptor Targeting, Antiangiogenic Peptides with TFPIc23-Like Activity.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 531-531
Author(s):  
Todd Hembrough ◽  
Kevin Yin ◽  
Art Hanson ◽  
Elizabeth Hahn-Dantona ◽  
Dudley Strickland ◽  
...  
Keyword(s):  
Binding Affinity ◽  
Receptor Binding ◽  
Antiproliferative Activity ◽  
Inhibitory Activity ◽  
Peptide Sequence ◽  
Wild Type ◽  
In Vivo Models ◽  
Vldl Receptor

Abstract We previously reported that a 23 amino acid fragment of tissue factor pathway inhibitor (TFPIc23) had significant antiangiogenic and antitumor activity in preclinical models. In in vitro studies, the very low density lipoprotein (VLDL) receptor was identified as the target for the activity of TFPIc23 (Blood103:3374). In order to confirm that the cellular target of TFPIc23 is the VLDL receptor, aortas from wildtype and VLDL receptor knockout (VLDLr −/−) mice were used for the ex vivo aorta ring model of angiogenesis. Vessel outgrowth from these rings was measured in the presence and absence of TFPIc23. In control studies, both wild type and VLDLr −/− mouse aorta rings grew vessels. When aorta rings from wild type mice were treated with TFPIc23, there was greater than 90% inhibition of vessel outgrowth. In contrast, VLDLr −/− aorta rings were insensitive to inhibition by the TFPIc23 peptide consistent with the hypothesis that the in vivo target of TFPIc23 activity is the VLDL receptor. To further assess the role of the VLDL receptor in angiogenesis, chemical modification of the TFPIc23 sequence was performed to define the structure activity relationships between the peptide sequence, peptide binding affinity for the VLDL receptor, and inhibitory activity in HUVEC proliferation assays. The goals were to define a minimal peptide structure which retained antiproliferative activity, confirm the VLDL receptor as the target of action, and modify the peptide sequence and architecture to increase activity and differentiate the peptide from the native sequence. 151 peptides were synthesized and screened for VLDL receptor binding affinity, as well as inhibitory activity in the HUVEC assay. Several peptides of 11–15 amino acids that retained both VLDL receptor affinity, and antiproliferative activity were identified. In the HUVEC assay the IC50 value of some of the novel peptides was decreased from 15uM for TFPIc23 to <1uM. The affinity of these peptides for the VLDL receptor was enhanced more than 10-fold. To confirm that the peptide’s antiproliferative activity was mediated by the VLDL receptor, blocking studies were performed with antibodies to the VLDL receptor. Blockade of the VLDL receptor abrogated the activity of several of the peptides with increase antiproliferative activity. Overall there was a good correlation between binding and activity, further supporting the VLDL receptor as mediating the antiangiogenic activity of these peptides. Several novel peptide analogs of TFPIc23 that exhibited improved antiproliferative activity and VLDL receptor binding in vitro were then assessed in in vivo models. In the Matrigel angiogenesis model, one of these peptides significantly inhibited angiogenesis by ~75% at 200mg/ml and in the Lewis lung carcinoma metastatic model inhibited metastatic tumor growth by >50% at 100mg/ml. In both cases these activities were significantly better than the activity of the parental TFPIc23 peptide. Taken together, these data show that SAR studies on novel synthetic peptides have yielded peptides with significantly better activity in preclinical tumor and angiogenesis models than TFPIc23. In addition, these results suggest that the VLDL receptor is a potential target for the development of antiangiogenic and antitumor agents.

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