Chemistry: molecular biology and microbiology – Micro-organism – tissue cell culture or enzyme using process... – Recombinant dna technique included in method of making a...
Reexamination Certificate
1999-12-07
2002-08-13
Spector, Lorraine (Department: 1647)
Chemistry: molecular biology and microbiology
Micro-organism, tissue cell culture or enzyme using process...
Recombinant dna technique included in method of making a...
C435S069500, C435S006120, C435S320100, C435S325000, C530S351000, C530S399000
Reexamination Certificate
active
06432673
ABSTRACT:
BACKGROUND OF THE INVENTION
In multicellular animals, cell growth, differentiation, and migration are controlled by polypeptide growth factors. These growth factors play a role in both normal development and pathogenesis, including the development of solid tumors.
Polypeptide growth factors influence cellular events by binding to cell-surface receptors, many of which are tyrosine kinases. Binding initiates a chain of signalling events within the cell, which ultimately results in phenotypic changes, such as cell division, protease production, and cell migration.
Growth factors can be classified into families on the basis of structural similarities. One such family, the PDGF (platelet derived growth factor) family, is characterized by a dimeric structure stabilized by disulfide bonds. This family includes PDGF, the placental growth factors (PlGFs), and the vascular endothelial growth factors (VEGFs). The individual polypeptide chains of these proteins form characteristic higher-order structures having a bow tie-like configuration about a cystine knot, formed by disulfide bonding between pairs of cysteine residues. Hydrophobic interactions between loops contribute to the dimerization of the two monomers. See, Daopin et al.,
Science
257:369, 1992; Lapthorn et al.,
Nature
369:455, 1994. Members of this family are active as both homodimers and heterodimers. See, for example, Heldin et al.,
EMBO J
. 7:1387-1393, 1988; Cao et al.,
J. Biol. Chem
. 271:3154-3162, 1996. The cystine knot motif and bow tie fold are also characteristic of the growth factors transforming growth factor-beta (TGF-&bgr;) and nerve growth factor (NGF), and the glycoprotein hormones. Although their amino acid sequences are quite divergent, these proteins all contain the six conserved cysteine residues of the cystine knot.
Four vascular endothelial growth factors have been identified: VEGF, also known as vascular permeability factor (Dvorak et al.,
Am. J. Pathol
. 146:1029-1039, 1995); VEGF-B (Olofsson et al.,
Proc. Natl. Acad. Sci. USA
93:2567-2581, 1996; Hayward et al., WIPO Publication WO 96/27007); VEGF-C (Joukov et al.,
EMBO J
. 15:290-298, 1996); and VEGF-D (Oliviero, WO 97/12972; Achen et al., WO 98/07832). Five VEGF polypeptides (121, 145, 165, 189, and 206 amino acids) arise from alternative splicing of the VEGF mRNA.
VEGFs stimulate the development of vasculature through a process known as angiogenesis, wherein vascular endothelial cells re-enter the cell cycle, degrade underlying basement membrane, and migrate to form new capillary sprouts. These cells then differentiate, and mature vessels are formed. This process of growth and differentiation is regulated by a balance of pro-angiogenic and anti-angiogenic factors. Angiogenesis is central to normal formation and repair of tissue, occuring in embryo development and wound healing. Angiogenesis is also a factor in the development of certain diseases, including solid tumors, rheumatoid arthritis, diabetic retinopathy, macular degeneration, and atherosclerosis.
A number of proteins from vertebrates and invertebrates have been identified as influencing neural development. Among those molecules are members of the neuropilin family and the semaphorin/collapsin family. Neuronal cell outgrowths, known as processes, grow away from the cell body to form synaptic connections. Long, thin processes that carry information away from the cell body are called axons, and short, thicker processes which carry information to and from the cell body are called dendrites. Axons and dendrites are collectively referred to as neurites. Neurites are extended by means of growth cones, the growing tips of neurites, which are highly motile and are ultimately responsible for increasing and extending the neuronal network in the body.
Three receptors for VEGF have been identified: KDR/Flk-1 (Matthews et al.,
Proc. Natl. Acad. Sci. USA
88:9026-9030, 1991), Flt-1 (de Vries et al.,
Science
255:989-991, 1992), and neuropilin-1 (Soker et al.,
Cell
92:735-745, 1998). Neuropilin-1 is a cell-surface glycoprotein that was initially identified in Xenopus tadpole nervous tissues, then in chicken, mouse, and human. The primary structure of neuropilin-1 is highly conserved among these vertebrate species. Neuropilin-1 has been demonstrated to be a receptor for various members of the semaphorin family including semaphorin III (Kolodkin et al.,
Cell
90:753-762, 1997), Sema E and Sema IV (Chen et al.,
Neuron
19:547-559, 1997). A variety of activities have been associated with the binding of neuropilin-1 to its ligands. For example, binding of semaphorin III to neuropilin-1 can induce neuronal growth cone collapse and repulsion of neurites in vitro (Kitsukawa et al.,
Neuron
19: 995-1005, 1997).
In mice, neuropilin-1 is expressed in the cardiovascular system, nervous system, and limbs at particular developmental stages. Chimeric mice over-expressing neuropilin-1 were found to be embryonic lethal (Kitsukawa et al.,
Development
121:4309-4318, 1995). The chimeric embryos exhibited several morphological abnormalities, including excess capillaries and blood vessels, dilation of blood vessels, malformed hearts, ectopic sprouting and defasciculation of nerve fibers, and extra digits. All of these abnormalities occurred in the organs in which neuropilin-1 is expressed in normal development. Mice lacking the neuropilin-1 gene have severe cardiovascular abnormalities, including impairment of vascular network formation in the central and peripheral nervous systems (Takashima et al., American Heart Association 1998 Meeting, Abstract #3178).
Neuropilin-1 has been identified as a cell-surface receptor for VEGF (Soker et al., ibid.), and displays selective binding activity for VEGF
165
over VEGF
121
. It has been shown to be expressed on vascular endothelial cells and tumor cells in vitro. When neuropilin-1 is co-expressed in cells with KDR, neuropilin-1 enhances the binding of VEGF
165
to KDR and VEGF
165
-mediated chemotaxis. Conversely, inhibition of VEGF
165
binding to neuropilin-1 inhibits its binding to KDR and its mitogenic activity for endothelial cells (Soker, et al., ibid.). Neuropilin-1 is also a receptor for PlGF-2 (Migdal et al.,
J. Biol. Chem
. 273: 22272-22278, 1998). A second semaphorin receptor, neuropilin-2, exhibits homology with neuropilin-1 but has differs in binding specificity (Chen et al.
Neuron
19: 547-559, 1997).
Semaphorins are a large family of molecules which share the defining semaphorin domain of approximately 500 amino acids. This family can be subdivided into multiple subfamilies that contain both secreted and membrane-bound proteins. Select members of these subfamilies, class III (SemD) and class IV (SemD), form homodimers linked by disulfide bridges. In the case of SemD, there is additional proteolytic processing that creates a 65-kDa isoform that lacks the 33-kDa carboxyl-terminal sequence. Dimerization is believed to be important for functional activity (Klostermann et al.,
J. Biol. Chem
. 273:7326-7331, 1998). Collapsin-1, the first identified vertebrate member of the semaphorin family of axon guidance proteins, has also been shown to form covalent dimers, with dimerization necessary for collapse activity (Koppel et al.,
J. Biol. Chem
. 273:15708-15713, 1998).
Semaphorin III has been associated in vitro with regulating growth clone collapse and chemorepulsion of neurites. In vivo it has also been shown to be required for correct sensory afferent innervation and other aspects of development, including skeletal and cardiac defects (Fehar et al.,
Nature
383:525-528, 1996). Other members of the semaphorin family have been shown to be associated with other forms of biology. The human semaphorin E gene is expressed in rheumatoid synovial cells and is thought to play an immunosuppressive role via inhibition of cytokines (Mangasser-Stephan et al.,
Biochem. Biophys. Res. Comm
. 234:153-156, 1997). CD100, a leukocyte semaphorin promotes B-cell aggregation and differentiation (Hall et al.,
Proc. Natl. Acad. Sci. USA
93:11780-11785, 1996). CD100 has also
Gao Zeren
Gilbertson Debra G.
Hart Charles E.
Piddington Christopher S.
Sheppard Paul O.
Jiang Dong
Parker Gary E.
Spector Lorraine
ZymoGenetics Inc.
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