Chemistry: natural resins or derivatives; peptides or proteins; – Peptides of 3 to 100 amino acid residues
Reexamination Certificate
1999-10-20
2002-12-17
Reynolds, Deborah J. (Department: 1632)
Chemistry: natural resins or derivatives; peptides or proteins;
Peptides of 3 to 100 amino acid residues
C514S002600
Reexamination Certificate
active
06495662
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to novel parathyroid hormone peptide (PTH) derivatives and to novel parathyroid hormone-related peptide (PTHrP) derivatives. In particular, the invention relates to PTH and PTHrP minimized peptide and derivatives thereof that still retain biological activity.
2. Description of Related Art
Parathyroid hormone (PTH) is a major regulator of calcium homeostasis whose principal target cells occur in bone and kidney. Regulation of calcium concentration is necessary for the normal function of the gastrointestinal, skeletal, neurologic, neuromuscular, and cardiovascular systems. PTH synthesis and release are controlled principally by the serum calcium level; a low level stimulates and a high level suppresses both hormone synthesis and release. PTH, in turn, maintains the serum calcium level by directly or indirectly promoting calcium entry into the blood at three sites of calcium exchange: gut, bone, and kidney. PTH contributes to net gastrointestinal absorption of calcium by favoring the renal synthesis of the active form of vitamin D. PTH promotes calcium resorption from bone indirectly by stimulating differentiation of the bone-resorbing cells, osteoclasts. It also mediates at least three main effects on the kidney: stimulation of tubular calcium reabsorption, enhancement of phosphate clearance, and promotion of an increase in the enzyme that completes synthesis of the active form of vitamin D. PTH exerts these effects primarily through receptor-mediated activation of adenylate cyclase and phospholipase C.
Disruption of calcium homeostasis may produce many clinical disorders (e.g., severe bone disease, anemia, renal impairment, ulcers, myopathy, and neuropathy) and usually results from conditions that produce an alteration in the level of parathyroid hormone. Hypercalcemia is a condition that is characterized by an elevation in the serum calcium level. It is often associated with primary hyperparathyroidism in which an excess of PTH production occurs as a result of a lesion (e.g., adenoma, hyperplasia, or carcinoma) of the parathyroid glands. Another type of hypercalcemia, humoral hypercalcemia ofmalignancy (HHM) is the most common paraneoplastic syndrome. It appears to result in most instances from the production by tumors (e.g., squamous, renal, ovarian, or bladder carcinomas) of a class of protein hormone which shares amino acid homology with PTH. These PTH-related proteins (PTHrP) appear to mimic certain of the renal and skeletal actions of PTH and are believed to interact with the PTH receptor in these tissues. PTHrP is normally found at low levels in many tissues, including keratinocytes, brain, pituitary, parathyroid, adrenal cortex, medulla, fetal liver, osteoblast-like cells, and lactating mammary tissues. In many HHM malignancies, PTHrP is found in the circulatory system at high levels, thereby producing the elevated calcium levels associated with HHM.
The pharmacological profiles of PTH and PTHrP are nearly identical in most in vitro assay systems, and elevated blood levels of PTH (i.e., primary hyperparathyroidism) or PTHrP (i. e., HHM) have comparable effects on mineral ion homeostasis (Broadus, A. E. & Stewart, A. F., “Parathyroid hormone-related protein: Structure, processing and physiological actions,” in Basic and Clinical Concepts, Bilzikian, J. P. et al., eds., Raven Press, New York (1994), pp.259-294; Kronenberg, H. M. et al., “
Parathyroid hormone: Biosynthesis, secretion, chemistry and action
,” in Handbook of Experimental Pharmacology, Mundy, G. R. & Martin, T. J., eds., Springer-Verlag, Heidelberg (1993), pp. 185-201). The similarities in the biological activities of the two ligands can be explained by their interaction with a common receptor, the PTH/PTHrP receptor, which is expressed abundantly in bone and kidney (Urena, P. et al.,
Endocrinology
134:451-456 (1994)).
Native human parathyroid hormone is an unmodified polypeptide of 84 amino acids. It is secreted from the parathyroid glands in response to low blood calcium levels and acts on osteoblast (bone-building cells) in bone, and on tubular epithelial cells of kidney. The hormone interacts with a cell surface receptor molecule, called the PTH-1 receptor or PTH/PTHrP receptor, which is expressed by both osteoblast and renal tubular cells. PTHrP, the major cause of the humoral hypercalcemia of malignancy, also has normal functions that include roles in development. PTHrP has 141 amino acids, though variants also occur that result from alternative gene splicing mechanisms. PTHrP plays a key role in the formation of the skeleton through a process that also involves binding to the PTH-1 receptor (Karaplis, A. C., et al.,
Genes and Dev
. 8:277-289 (1994) and Lanske, B., et al.,
Science
273:663-666 (1996)).
The PTH-1 receptor is homologous in primary structure to a number of other receptors that bind peptide hormones, such as secretin (Ishihara, T. et al.,
EMBO J
. 10:1635-1641 (1991)), calcitonin (Lin, H. Y. et al.,
Science
254:1022-1024 (1991)) and glucagon (Jelinek, L. J. et al.,
Science
259:1614-1616 (1993)); together these receptors form a distinct family called receptor family B (Kolakowski, L. F.,
Receptors and Channels
2:1-7 (1994)). Within this family, the PTH-1 receptor is unique, in that it binds two peptide ligands and thereby regulates two separate biological processes. A recently identified PTH receptor subtype, called the PTH-2 receptor, binds PTH but not PTHrP (Usdin, T., et al.,
J. Biol. Chem
. 270:15455-15458(1995)). This observation implied that structural differences in the PTH and PTHrP ligands determined selectivity for interaction with the PTH-2 receptor. The PTH-2 receptor has been detected by RNA methods in the brain, pancreas and vasculature, however, its biological function has not been determined (Usdin, T., et al.,
J. Biol. Chem
. 270:15455-15458 (1995)). It is hypothesized that the family B receptors use a common molecular mechanism to engage their own cognate peptide hormone (Bergwitz, C., et al.,
J. Biol. Chem
. 271:26469-26472 (1996)).
The binding of either radio labeled PTH(1-34) or PTHrP(1-36) to the PTH-1 receptor is competitively inhibited by either unlabeled ligand (Jüppner, H. et al.,
J. Biol. Chem
. 263:8557-8560 (1988); Nissenson, R. A. et al.,
J. Biol. Chem
. 263:12866-12871 (1988)). Thus, the recognition sites for the two ligands in the PTH-1 receptor probably overlap. In both PTH and PTHrP, the 15-34 region contains the principal determinants for binding to the PTH-1 receptor. Although these regions show only minimal sequence homology (only 3 amino acid identities), each 15-34 peptide can block the binding of either PTH(1-34) or PTHrP(1-34) to the PTH-1 receptor (Nussbaum, S. R. et al.,
J. Biol. Chem
. 255:10183-10187 (1980); Caulfield, M. P. et al.,
Endocrinology
127:83-87 (1990); Abou-Samra, A.-B. et al.,
Endocrinology
125:2215-2217 (1989)). Further, the amino terminal portion of each ligand is required for bioactivity, and these probably interact with the PTH-1 receptor in similar ways, since 8 of 13 of these residues are identical in PTH and PTHrP.
Both PTH and PTHrP bind to the PTH-1 receptor with affinity in the nM range; the ligand-occupied receptor transmits a “signal” across the cell membrane to intracellular effector enzymes through a mechanism that involves intermediary heterotrimeric GTP-binding proteins (G proteins). The primary intracellular effector enzyme activated by the PTH-1 receptor in response to PTH or PTHrP is adenylyl cyclase (AC). Thus, PTH induces a robust increase in the “second messenger” molecule, cyclic adenosine monophosphate (cAMP) which goes on to regulate the poorly characterized “downstream” cellular processes involved in bone-remodeling (both bone formation and bone resorption processes). In certain cell-based assay systems, PTH can stimulate effector enzymes other than AC, including phospholipase C (PLC), which results in production of inositol triphosphate (IP
3
), diacylglycerol (DAG) and intracellular calcium (iCa
2+
Gardella Thomas J.
Jüppner Harald
Kronenberg Henry M.
Potts, Jr. John T.
Reynolds Deborah J.
Sorbello Eleanor
Sterne Kessler Goldstein & Fox PLLC
The General Hospital Corporation
LandOfFree
Bioactive peptides and peptide derivatives of parathyroid... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Bioactive peptides and peptide derivatives of parathyroid..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Bioactive peptides and peptide derivatives of parathyroid... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2992315