Immunochemical mapping of antigenic regions on the human thyrotropin beta-subunit by antipeptide antibodies

Increased receptor binding by bovine (b) TSH bound to monoclonal antibody to bTSHbeta-subunit

TSH receptor (R) binding and cAMP production by bovine (b) TSH-bound to a monoclonal antibody (MoAb) or polyclonal antibody (Ab) to bTSH were examined, using TSH receptor (R) coating tube and porcine thyroid cells. (125) I-bTSH bound-to MoAbs to bTSH(alpha) or discontinuous type MoAb showed TSHR binding (10%) similar to intact (125) I-bTSH. TSHR binding was completely decreased (<2%) when (125) I-bTSH was bound by polyclonal Abs to bTSH(alpha) in Graves' patient or rabbit polyclonal Abs to bTSH. When either of the two MoAb (No. 1 and 2) to bTSH(beta) was bound to (125) I-bTSH, TSHR binding was 4 times higher (40%) compared to intact (125) I-bTSH. Binding of another MoAb (No. 3) caused no increased binding. TSHR binding of intact (125) I-bTSH was decreased from 10% to 2% by excess amounts of bTSH. Binding of (125) I-bTSH bound to MoAb to bTSH(beta) (No. 1 and 2) decreased from 40% to 30% by excess amounts of bTSH. When (125) I-bTSH bound-Fab of MoAb was used, the binding was reduced from 30 to 10% (No. 1) and from 25 to 6% (No. 2), respectively. In contrast, cAMP production by bTSH was decreased by pre-binding of all MoAbs and polyclonal Abs. Binding of (125) I-MoAb to bTSH (beta) to a synthetic peptide array of bTSH (beta) sequence was examined by the radioautography. The epitope of MoAb to bTSH(beta) was suggested to be LPK (beta 42-44) for No. 1, KLF (beta 39-41) for No. 2 and PKYA (beta 43-46) for No. 3, respectively, although the existence of discontinuous epitope could not be ruled out. The increased TSHR binding and the decreased cAMP production by bTSH bound to MoAbs may be due to the conformational change of TSH molecule or TSHR by binding of both bTSH and MoAb.

Synthesis and application of peptide immunogens related to the sperm tail protein tpx-1, a member of the CRISP superfamily of proteins

The synthesis of peptides containing 0, 1 and 2 cysteine residues related to the human sperm tail protein, tpx-1, is described. These synthetic peptides, following conjugation to keyhole limpet hemocyanin modified with maleimidobenzoic acid N-hydroxysuccinimide ester, were used as immunogens to generate polyclonal antibodies in female New Zealand white rabbits. The binding characteristics of the derived antipeptide sera were evaluated using indirect and competitive ELISA procedures. Western immunoblot experiments also confirmed that these synthetic peptide immunogens are able to generate high-titer polyclonal antibodies capable of cross-reacting with the mature tpx-1 protein present in crude rat sperm tail/testis preparations as well as in outer dense fiber preparations. Consequently, these synthetic peptides represent promising candidates for investigations into the role of tpx-1 in the immunoregulation of sperm function in the rat and other mammalian models, with the derived antisera also providing an avenue to explore possible sites of expression of tpx-1 proteins in other tissues.

Molecular architecture and biorecognition processes of the cystine knot protein superfamily: part I. The glycoprotein hormones

In this review article, the reader is introduced to recent advances in our knowledge on a subset of the cystine knot superfamily of homo- and hetero-dimeric proteins, from the perspective of the endocrine glycoprotein hormone family of proteins: follitropin (FSH), Iutropin (LH), thyrotropin. (TSH) and chorionic gonadotropin (CG). Subsequent papers will address the structure-function behaviour of other members of this increasingly significant family of proteins, including various members of the transforming growth factor-beta (TGF-beta) family of proteins, the activins, inhibins, bone morphogenic growth factor, platelet derived growth factor-beta, nerve growth factor and more than 35 other proteins with similar topological features. In the present review article, specific emphasis has been placed on advances with the glycoprotein hormones (GPHs) that have facilitated greater insight into their physiological functions, molecular structures and most importantly the basis of the molecular recognition events that lead to the formation of hetero-dimeric structures as well as their specific and selective recognition by their corresponding receptors and antibodies. Thus, this review article focuses on the structural motifs involved in receptor recognition and the current techniques available to identify these regions, including the role of immunological methodology, peptide fragment design and synthesis and mutagenesis to delineate their structure-function relationships and molecular recognition behaviour.

Na+/I- symporter distribution in human thyroid tissues: an immunohistochemical study

Antipeptide antibodies raised against the carboxyl-terminal region of the human sodium/iodide (Na+/I-) symporter (hNIS) were used to investigate by immunohistochemistry the presence and distribution of the hNIS protein in normal thyroid tissues, in some pathological nonneoplastic thyroid tissues, and in different histotypes of thyroid neoplasms. In normal thyroid tissue, staining of hNIS protein was heterogeneous and limited to a minority of follicular cells that were in close contact with capillary vessels. In positive cells, immunostaining was limited to the basolateral membrane. In contrast, in Graves' disease the majority of follicular cells expressed the hNIS protein. In autoimmune thyroiditis, the number of hNIS-positive cells, was similar to that found in normal tissue. These positive cells were found essentially close to lymphocytic infiltrates. This observation supports the concept of hNIS as an autoantigen. In diffuse nodular hyperplasia, hNIS staining was heterogeneous, but the number of hNIS-positive cells exceeded that found in normal tissue. In well differentiated follicular or papillary carcinoma, the number of hNIS-positive cells was significantly lower than in normal tissue. In poorly differentiated follicular carcinoma, the number ofhNIS-positive cells was less than that found in well differentiated carcinoma, or there were no positive cells. Interestingly, in all of these thyroid tissues, the number of follicular cells exhibiting TSH receptor (TSHR) immunoreactivity was greater than the number ofhNIS-positive cells. As hNIS expression appears to be related to TSHR stimulation, the decreased number of TSHR-positive cells in cancers may contribute to the reduced capacity of neoplastic cells to concentrate iodide. In one patient with a follicular cancer with an absence of hNIS immunostaining, the total body 131I scan showed no uptake in metastatic tissue. In three cancers with positive hNIS cells, the 131I scan showed uptake in lymph node metastases. This suggests that immunodetection of hNIS could predict radioiodine uptake in thyroid cancers.

Immunochemical mapping of human lutropin: II. Characterization of two monoclonal antipeptide antibodies reacting with the native beta-subunit

To investigate the epitopes present on the beta-subunit of the human lutropin (hLHbeta) and their topographical relationship at the surface of the molecule, we produced two monoclonal antipeptide antibodies, designated LHP03 and LHP04, capable of binding to the radiolabeled 125I-hLHbeta and directed to the 43-52 and 110-117 regions of the hLHbeta, respectively. Analysis of the accessibility of the epitopes on hLH and on the beta-subunit of human chorionic gonadotropin (hCGbeta), equine LH (eLHbeta) and ovine LH (oLHbeta) indicated that: (i) LHP03 binds to both the free hLHbeta subunit and dimeric hLH whereas LHP04 binds preferentially to the free hLHbeta, (ii) LHP03 recognizes weakly the hCGbeta and oLHbeta in comparison to hLHbeta and (iii) LHP04 binds oLHbeta as well as hLHbeta but does not bind to hCGbeta and eLHbeta. The topographical relationship of epitopes recognized by LHP03 and monoclonal antibodies recognizing dimer specific epitopes on hLH allowed us to localize discontinuous antigenic sites that overlaps or are located outside the hHLbeta(43-52) region. Together, our results demonstrated that the hHLbeta(43-52) portion is accessible on both the free hLHbeta subunit and hLH whereas the COOH-terminal portion, hHLbeta(110-117), is probably buried at the alpha/beta interface of the hormone.

Immunochemical mapping of human lutropin: I. Delineation of a conformational antigenic determinant

Lutropin (LH), follitropin (FSH), thyrotropin (TSH) and choriogonadotropin (CG) are assembled of two non-covalently alpha (alpha) and beta (beta) subunits. We studied the discontinuous antigenic regions recognized by a monoclonal anti-hLH antibody designated as LH05 which binds to hLH, hCG and hTSH and does not cross-react with either the free subunits or hFSH. LH05 and an antibody designated HT13, recognizing an epitope partly comprizing the alpha64-76 region, did not bind simultaneously to hCG. Furthermore, LH05 was unable to combine with an anti-peptide antibody (LHP03) directed to residues 43-52 of hLHbeta. Thus, LH05 recognizes an epitope partly overlapping with those recognized by HT13 and LHP03. Using various hybrid molecules, we showed that the human alpha-subunit plays a critical role in the assembly of the epitope that, in contrast, contains amino acid residues conserved in the various beta-subunit of several species. Together, our results suggest that the amino acids Leu49-Pro50, Tyr59-Arg60 and Leu86-Ser87 in the hLHbeta and the alpha64-76 region are probably included in the epitope recognized by LH05 which appeared to be not accessible on the CG/LH receptor.