ABSTRACT
Efforts have been focused on the development of prolactin receptor (PRLR) antagonists, which, it is hoped, will be useful therapeutics for breast, prostate and possibly other cancers. Several approaches have been undertaken, including the production of pure antagonists and the combination of a PRLR antagonist with other antitumor molecules to increase efficacy. An alternative approach has been the development of a mimic of the natural PRL growth antagonist. This molecule is a combined antagonist/agonist since it inhibits signaling leading to growth, but promotes signaling leading to cell-cycle control, differentiation and apoptosis.
Subject(s)
Prolactin/analogs & derivatives , Prolactin/therapeutic use , Receptors, Prolactin/antagonists & inhibitors , Receptors, Prolactin/therapeutic use , Humans , Prolactin/chemical synthesis , Receptors, Prolactin/physiologyABSTRACT
A major obstacle in the production of specific antibodies toward chicken prolactin (PRL) has been overcome by mimicking a putative epitope of the molecule using the synthetic decapeptide Lys-chPRL 59-67. This peptide represents the highest hydrophilicity peak of the amino acid sequence of chPRL that was recently derived from the nucleotide sequence. Polyclonal mouse antisera against the fragment specifically recognized the lactotropes in the cephalic lobe of the chicken pars distalis as illustrated by immunocytochemical double staining experiments. Monoclonal antibody production yielded antibodies that specifically labeled purified turkey PRL upon SDS-PAGE separation and immunoblotting. Turkey and chicken PRL showed a very similar polymorphism with respect to their apparent molecular weights, including the occurrence of a glycosylated variant of chicken PRL. The monoclonal antibodies were finally used to demonstrate the presence of PRL-like immunoreactivity both in the pituitary gland and in the brain of the quail. In the brain, immunoreactive neurons were in the nucleus accumbens and in the lateral parts of the ventro-medial hypothalamus, partly similar to those described in the rat.
Subject(s)
Prolactin/metabolism , Amino Acid Sequence , Animals , Antibodies, Monoclonal , Cross Reactions , Female , Hypothalamus/metabolism , Immunoblotting , Immunohistochemistry , Molecular Sequence Data , Peptide Fragments , Prolactin/chemical synthesis , Prolactin/chemistry , QuailABSTRACT
The alpha-amino group of ovine prolactin (oPRL) and human growth hormone (hGH) was selectively modified by transamination with glyoxylic acid. No difference was found in the binding capacity of transaminated oPRL to rat liver lactogenic receptors with respect to its control, although both samples showed a decrease in its binding capacity with reference to the native hormone. This decrease was due to conformational changes caused by the reaction conditions and not by the transamination itself, as shown by the circular dichroism spectra. Transaminated hGH retained the full binding capacity of the hormone. These results suggest that the alpha-amino group is not relevant for the binding to lactogenic liver receptors in both lactogenic hormones.
Subject(s)
Growth Hormone/analogs & derivatives , Growth Hormone/chemical synthesis , Prolactin/analogs & derivatives , Prolactin/chemical synthesis , Animals , Binding, Competitive , Circular Dichroism , Humans , Kinetics , Liver/metabolism , Prolactin/metabolism , Protein Conformation , Receptors, Prolactin/metabolism , Sheep , Structure-Activity RelationshipABSTRACT
A 13 amino acid analog of the human prolactin amino terminus was synthesized, substituting tyrosine for valine at residue 13. The peptide was coupled to crystalline bovine serum albumin for antisera production. The peptide was used for iodination with 125I, and displacement curves were found to be parallel when human prolactin and the synthetic peptide were compared as standards. The radioimmunoassay using the synthetic peptide has the advantages of purity in its roles as hapten in the antigen and as labelled peptide, of ease of iodination of the peptide, of its stability after iodination, and of obviating the need for native human prolactin. The radioimmunoassay is suitable for the measurement of human prolactin concentration in plasma.
Subject(s)
Peptides/chemical synthesis , Prolactin/blood , Amino Acid Sequence , Humans , Peptides/analysis , Prolactin/chemical synthesis , Radioimmunoassay/methodsABSTRACT
The carboxyl terminal cyclic undecapeptide of the ovine prolactin molecule: Leu-Asn-Cys-Arg-Ile-Ile-Tyr-Asn-Asn-Asn-Cys has been synthesized by the solid-phase method. The circular dichroism of the synthetic peptide has been investigated. It was also found that the cyclic undecapeptide does not have pigeon crop-sac stimulating activity, or immunological activity when tested by complement fixation experiments.
