scholarly journals Multiple Transmembrane Amino Acid Requirements Suggest a Highly Specific Interaction between the Bovine Papillomavirus E5 Oncoprotein and the Platelet-Derived Growth Factor Beta Receptor

2002 ◽  
Vol 76 (16) ◽  
pp. 7976-7986 ◽  
Author(s):  
Valerie M. Nappi ◽  
Lisa M. Petti
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Growth Factor ◽  
Transmembrane Domain ◽  
Specific Interaction ◽  
Platelet Derived Growth Factor ◽  
Helical Conformation ◽  
Bovine Papillomavirus ◽  
E5 Protein ◽  
Amino Acid Requirements

ABSTRACT The bovine papillomavirus E5 protein activates the cellular platelet-derived growth factor β receptor (PDGFβR) tyrosine kinase in a ligand-independent manner. Evidence suggests that the small transmembrane E5 protein homodimerizes and physically interacts with the transmembrane domain of the PDGFβR, thereby inducing constitutive dimerization and activation of this receptor. Amino acids in the receptor previously found to be required for the PDGFβR-E5 interaction are a transmembrane Thr513 and a juxtamembrane Lys499. Here, we sought to determine if these are the only two receptor amino acids required for an interaction with the E5 protein. Substitution of large portions of the PDGFβR transmembrane domain indicated that additional amino acids in both the amino and carboxyl halves of the receptor transmembrane domain are required for a productive interaction with the E5 protein. Indeed, individual amino acid substitutions in the receptor transmembrane domain identified roles for the extracellular proximal transmembrane residues in the interaction. These data suggest that multiple amino acids within the transmembrane domain of the PDGFβR are required for a stable interaction with the E5 protein. These may be involved in direct protein-protein contacts or may support the proper transmembrane alpha-helical conformation for optimal positioning of the primary amino acid requirements.

scholarly journals Artificial Transmembrane Oncoproteins Smaller than the Bovine Papillomavirus E5 Protein Redefine Sequence Requirements for Activation of the Platelet-Derived Growth Factor β Receptor

2009 ◽  
Vol 83 (19) ◽  
pp. 9773-9785 ◽  
Author(s):  
Kristina Talbert-Slagle ◽  
Sara Marlatt ◽  
Francisco N. Barrera ◽  
Ekta Khurana ◽  
Joanne Oates ◽  
...  
Keyword(s):  
Amino Acid ◽  
Growth Factor ◽  
Transmembrane Domain ◽  
Transmembrane Protein ◽  
Receptor Activation ◽  
Platelet Derived Growth Factor ◽  
Bovine Papillomavirus ◽  
Viral Oncoprotein ◽  
E5 Protein ◽  
Β Receptor

ABSTRACT The bovine papillomavirus E5 protein (BPV E5) is a 44-amino-acid homodimeric transmembrane protein that binds directly to the transmembrane domain of the platelet-derived growth factor (PDGF) β receptor and induces ligand-independent receptor activation. Three specific features of BPV E5 are considered important for its ability to activate the PDGF β receptor and transform mouse fibroblasts: a pair of C-terminal cysteines, a transmembrane glutamine, and a juxtamembrane aspartic acid. By using a new genetic technique to screen libraries expressing artificial transmembrane proteins for activators of the PDGF β receptor, we isolated much smaller proteins, from 32 to 36 residues, that lack all three of these features yet still dimerize noncovalently, specifically activate the PDGF β receptor via its transmembrane domain, and transform cells efficiently. The primary amino acid sequence of BPV E5 is virtually unrecognizable in some of these proteins, which share as few as seven consecutive amino acids with the viral protein. Thus, small artificial proteins that bear little resemblance to a viral oncoprotein can nevertheless productively interact with the same cellular target. We speculate that similar cellular proteins may exist but have been overlooked due to their small size and hydrophobicity.

scholarly journals Productive Interaction between Transmembrane Mutants of the Bovine Papillomavirus E5 Protein and the Platelet-Derived Growth Factor β Receptor

2005 ◽  
Vol 79 (3) ◽  
pp. 1924-1929 ◽  
Author(s):  
Char-Chang Lai ◽  
Anne P. B. Edwards ◽  
Daniel DiMaio
Keyword(s):  
Amino Acid ◽  
Growth Factor ◽  
Transmembrane Protein ◽  
Platelet Derived Growth Factor ◽  
Bovine Papillomavirus ◽  
Transmembrane Region ◽  
E5 Protein ◽  
Β Receptor ◽  
Membrane Spanning ◽  
Lines Of Evidence

ABSTRACT The bovine papillomavirus E5 protein is a 44-amino-acid transmembrane protein that transforms cells by binding to the transmembrane region of the cellular platelet-derived growth factor (PDGF) β receptor, resulting in sustained receptor signaling. However, there are published reports that certain mutants with amino acid substitutions in the membrane-spanning segment of the E5 protein transform cells without activating the PDGF β receptor. We re-examined several of these transmembrane mutants, and here we present five lines of evidence that these mutants do in fact activate the PDGF β receptor, resulting in cellular signaling and transformation.

scholarly journals Role of Glutamine 17 of the Bovine Papillomavirus E5 Protein in Platelet-Derived Growth Factor β Receptor Activation and Cell Transformation

1998 ◽  
Vol 72 (11) ◽  
pp. 8921-8932 ◽  
Author(s):  
Ophir Klein ◽  
Glenda W. Polack ◽  
Toral Surti ◽  
Deena Kegler-Ebo ◽  
Steven O. Smith ◽  
...  
Keyword(s):  
Amino Acids ◽  
Growth Factor ◽  
Cell Transformation ◽  
Receptor Activation ◽  
Platelet Derived Growth Factor ◽  
Stable Complex ◽  
Bovine Papillomavirus ◽  
E5 Protein ◽  
Β Receptor

ABSTRACT The bovine papillomavirus E5 protein is a small, homodimeric transmembrane protein that forms a stable complex with the cellular platelet-derived growth factor (PDGF) β receptor through transmembrane and juxtamembrane interactions, resulting in receptor activation and cell transformation. Glutamine 17 in the transmembrane domain of the 44-amino-acid E5 protein is critical for complex formation and receptor activation, and we previously proposed that glutamine 17 forms a hydrogen bond with threonine 513 of the PDGF β receptor. We have constructed and analyzed mutant E5 proteins containing all possible amino acids at position 17 and examined the ability of these proteins to transform C127 fibroblasts, which express endogenous PDGF β receptor. Although several position 17 mutants were able to transform cells, mutants containing amino acids with side groups that were unable to participate in hydrogen bonding interactions did not form a stable complex with the PDGF β receptor or transform cells, in agreement with the proposed interaction between position 17 of the E5 protein and threonine 513 of the receptor. The nature of the residue at position 17 also affected the ability of the E5 proteins to dimerize. Overall, there was an excellent correlation between the ability of the various E5 mutant proteins to bind the PDGF β receptor, lead to receptor tyrosine phosphorylation, and transform cells. Similar results were obtained in Ba/F3 hematopoietic cells expressing exogenous PDGF β receptor. In addition, treatment of E5-transformed cells with a specific inhibitor of the PDGF receptor tyrosine kinase reversed the transformed phenotype. These results confirm the central importance of the PDGF β receptor in mediating E5 transformation and highlight the critical role of the residue at position 17 of the E5 protein in the productive interaction with the PDGF β receptor. On the basis of molecular modeling analysis and the known chemical properties of the amino acids, we suggest a structural basis for the role of the residue at position 17 in E5 dimerization and in complex formation between the E5 protein and the PDGF β receptor.

scholarly journals Platelet-derived growth factor receptor can mediate tumorigenic transformation by the bovine papillomavirus E5 protein.

1993 ◽  
Vol 13 (7) ◽  
pp. 4137-4145 ◽  
Author(s):  
L A Nilson ◽  
D DiMaio
Keyword(s):  
Growth Factor ◽  
Growth Factor Receptor ◽  
Platelet Derived Growth Factor ◽  
Stable Complex ◽  
Epithelial Cell Line ◽  
Bovine Papillomavirus ◽  
Pdgf Receptor ◽  
Beta Receptor ◽  
E5 Protein ◽  
Tumorigenic Transformation

We showed previously that the beta receptor for platelet-derived growth factor (PDGF) is constitutively activated in fibroblasts transformed by the 44-amino-acid bovine papillomavirus type 1 (BPV) E5 protein and that the E5 protein and the PDGF receptor exist in a stable complex in E5-transformed fibroblasts. On the basis of these results, we proposed that activation of the PDGF receptor by the BPV E5 protein generates a sustained proliferative signal, resulting in fibroblast transformation. In this study, we used a gene transfer approach to provide functional evidence that the PDGF receptor can mediate transformation by the E5 protein. We show that normal mouse mammary gland (NMuMG) cells, a murine mammary epithelial cell line that does not express PDGF receptors, are not susceptible to transformation by the E5 protein. Coexpression of the PDGF beta receptor and E5 genes in these cells results in markedly increased tyrosine phosphorylation of an immature PDGF receptor species and the formation of a stable complex between the E5 protein and this immature PDGF receptor form. Importantly, introduction of the PDGF receptor gene into NMuMG cells renders them highly susceptible to E5-mediated tumorigenic transformation. In contrast, the E5 protein does not induce transformation via the endogenous epidermal growth factor receptor pathway in these cells. These results demonstrate that the PDGF receptor, a cellular protein with a well-characterized role in the positive control of cell proliferation, can mediate transformation by a DNA virus transforming protein.

44-amino-acid E5 transforming protein of bovine papillomavirus requires a hydrophobic core and specific carboxyl-terminal amino acids

1988 ◽  
Vol 8 (10) ◽  
pp. 4071-4078
Author(s):  
B H Horwitz ◽  
A L Burkhardt ◽  
R Schlegel ◽  
D DiMaio
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Saturation Mutagenesis ◽  
Amino Acid Substitutions ◽  
Bovine Papillomavirus ◽  
Missense Mutations ◽  
Focus Formation ◽  
E5 Protein ◽  
Transforming Activity ◽  
Carboxyl Terminal

The 44-amino-acid E5 protein of bovine papillomavirus type 1 is the shortest known protein with transforming activity. To identify the specific amino acids required for in vitro focus formation in mouse C127 cells, we used oligonucleotide-directed saturation mutagenesis to construct an extensive collection of mutants with missense mutations in the E5 gene. Characterization of mutants with amino acid substitutions in the hydrophobic middle third of the E5 protein indicated that efficient transformation requires a stretch of hydrophobic amino acids but not a specific amino acid sequence in this portion of the protein. Many amino acids in the carboxyl-terminal third of the protein can also undergo substitution without impairment of focus-forming activity, but the amino acids at seven positions, including two cysteine residues that mediate dimer formation, appear essential for efficient transforming activity. These essential amino acids are the most well conserved among related fibropapillomaviruses. The small size of the E5 protein, its lack of similarity to other transforming proteins, and its ability to tolerate many amino acid substitutions implies that it transforms cells via a novel mechanism.

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