Chemistry: molecular biology and microbiology – Measuring or testing process involving enzymes or... – Involving antigen-antibody binding – specific binding protein...
Reexamination Certificate
2000-07-28
2003-05-20
Kemmerer, Elizabeth (Department: 1647)
Chemistry: molecular biology and microbiology
Measuring or testing process involving enzymes or...
Involving antigen-antibody binding, specific binding protein...
C435S007200, C435S007210, C435S035000, C435S320100
Reexamination Certificate
active
06566075
ABSTRACT:
INTRODUCTION
TECHNICAL FIELD
The present invention relates to growth factors and their receptors and, in particular, to human platelet-derived growth factor receptor.
BACKGROUND OF THE INVENTION
Platelet-derived growth factor (PDGF) is a major mitogen for cells of mesenchymal origin. The protein is a 32 kDa protein heterodimer composed of two polypeptide chains, A and B, linked by disulfide bonds. In addition to the PDGF AB heterodimer, two homodimeric forms of PDGF, denoted AA and BB, have been identified.
Until recently, whether the AA isoform bound to a receptor was not known. Now, a single receptor has been identified which has been shown to bind all three isoforms of hPDGF. However, the reported affinities of hPDGF receptors of different cell types for different isoforms of hPDGF has lead to speculation that there are more than one type of hPDGF receptor.
The first event in PDGF-mediated mitogenesis is the binding of PDGF to its receptor at the cell membrane. This interaction triggers a diverse group of early cellular responses including activation of receptor tyrosine kinase, increased phosphatidylinositol turnover, enhanced expression of a group of genes, activation of phospholipase A2, changes in cell shape, increase in cellular calcium concentration, changes in intracellular pH, and internalization and degradation of bound PDGF. These changes are followed by an increase in the rate of proliferation of the target cells.
While the ability of a polypeptide to stimulate growth of a particular cell type in vitro does not prove that it serves the same function in vivo, the role of many growth factors on cells is being studied to attempt to determine the role that the factors play in the whole organism. In vitro, platelet-derived growth factor is a major polypeptide mitogen in serum for cells of mesenchymal origin such as fibroblasts, smooth muscle cells and glial cells. In vivo, PDGF circulates stored in the &agr; granules of blood platelets and does not circulate freely in blood. During blood clotting and platelet adhesion, the granules are released, often at sites of injured blood vessels, implicating PDGF in the repair of blood vessels. PDGF also stimulates migration of arterial smooth muscle cells from the medial to the intimal layer of the artery where they then proliferate as an early response to injury.
PDGF is being studied to determine how cell proliferation is controlled in the body. The growth factor has been implicated in wound healing, in atherosclerosis, and in stimulating genes associated with cancerous transformation of cells, particularly c-myc and c-fos. Therefore, PDGF agonists may be useful in promoting wound healing. PDGF antagonists may be useful in preventing atherosclerosis, in retarding blood vessel narrowing that occurs after cardiovascular intervention and in controlling cancerous proliferation.
Relevant Literature
The mouse PDGF receptor has been identified, purified (Daniel et al.,
Proc. Natl. Acad. Sci USA
(1985) 82:2684-2687), and sequenced (Yarden et al.,
Nature
(1986) 323:226-232). A cDNA sequence encoding a human PDGF receptor was identified, sequenced and used to transfect cells lacking the receptor (Escobedo et al.,
Science
(1988) 240:1532-1538; Claesson-Welsh et al.,
Mol. Cell. Biol.
(1988) 8:3476-3486). Studies using the transfected cells gave differing results, demonstrating that the receptor binds specifically to all three isoforms of hPDGF, preferentially binding the BB homodimer (Escobedo et al., supra.) and that the receptor binds the BB and AB isoforms but not the AA isoform, at least at the concentration tested (Claesson-Welsh et al., supra.). Binding sites on different cell types were reported to have different affinities for different PDGF isoforms (Kazlauskas et al.,
EMBO J.
(1988) 7:3727-3735). Two classes of PDGF receptor were reported to recognize different isoforms of PDGF (Hart et al.,
Science
(1988) 240:1529-1531).
SUMMARY OF THE INVENTION
A DNA sequence encoding human platelet-derived growth factor receptor (hPDGF-R) has now been isolated and sequenced. An expression construct comprising the sequence encodes a receptor that can be secreted or incorporated into the membrane of a mammalian cell. The incorporated receptor is functionally equivalent to the wild-type receptor, conferring a PDGF-sensitive mitogenic response on cells lacking the receptor. The construct can be used for enhancing PDGF response of cells, determining the regions involved in transducing the signal in response to PDGF binding, providing mutated analogs and evaluating drugs for their physiologic activity.
REFERENCES:
patent: 5371205 (1994-12-01), Kelly
Murdoch, C. and Finn, A. (2000) Chemokine receptors and their role in inflammation and infectious diseases. Blood, 95(10): 3032-3042, esp. Table 1.*
Federal Register, 2001, 66(4): 1092-1098.*
Escobedo, “Platelet-Derived Growth Factor Receptors Expressed by cDNA Transfection Couple to a Diverse Group of Cellular Responses Associated with Cell Proliferation”J. Bio.. Chem. 263(3): 1482-1487 (1988).
Haynes et al, “Constitutive, Long-Term Production of Human Interferons by Hamster Cells Containing Multiple Copies of a Cloned Interferon Gene”Nucl. Acid. Res11(3):687-706 (1983).
Peralta et al., “Primary Structure and Biochemical Properties of an M2 Muscarinic Receptor”Science236:600-605 (1987).
Gronwald et al., “Cloning and Expression of a cDNA coding for the Human Platelet-Derived Growth Factor Receptor: Evidence for More Than One Receptor Class”Proc. Natl. Acad. Sci.85 3435-3439 (1988).
Matsui et al., “Isolation of a Novel Receptor cDNA Establishes the Existence of Two PDGF Receptor Genes”Science243:800-804 (1989).
Escobedo Jaime A.
Williams Lewis T.
Kemmerer Elizabeth
Wegert Sandra
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