The structure of procalcitonin of the salmon as deduced from its cDNA sequence

Analysis of the peptides (Prp106-126, MSI-78A, and Oxaldie 1) with the same biological activity by discrete Fourier transform: toward a selection rule in ligand-receptor interaction

Here, we first report a novel method in which the "desired cross-spectrum" of the peptides Prp106-126, MSI-78A, and oxaldie 1 with the same biological activities is obtained by the multiplication of two cross-spectra derived from the RNA sequence and from the cognate amino acid sequence by discrete Fourier transform (DFT), respectively. Based on a well-known method reported previously, we investigated the cross-spectrum by the multiplication of two of three desired cross-spectra. As a result, we found that one prominent peak occurring in the three cross-spectra showed the same frequency when a binary scale was used as a parameter of nucleotide or amino acid in the analysis. Moreover, we examined the relationship between a binary scale and other physicochemical ones. Almost the same results could be reproduced when the absolute electronegativity scale (or the absolute hardness one) was used, but not in the case of the hydrophobic or electron-ion interacting potential scale reported previously. This indicates that either the absolute electronegativity scale (or the absolute hardness one) or a binary scale, or both is very useful in extracting the information desired for various proteins by the present method from the amino acid and the RNA sequence.

Molecular aspects and natural source of procalcitonin

The search for sensitive and specific markers of systemic infection has shown that procalcitonin levels are increased in sepsis, and, consequently, this plasma protein has come into the focus of clinical research. Human procalcitonin is encoded by the Calc-l gene, which gives rise to two alternatively spliced transcripts. Despite systemic investigation of the Calc-l gene and mechanisms of the tissue-specific regulation and alternative splicing, little is known about the biology of procalcitonin and the cells which express this protein during inflammation. Here we focus on the molecular and biochemical properties of the molecule and summarize the known biological functions of procalcitonin. We report on the structure of the Calc-l gene, the amino acid conservation of procalcitonin in different species, and the consensus sequences of the protein with regard to sites relevant for posttranslational modification, spatial distribution, and homologies to other cytokines. We discuss aspects of intracellular location of procalcitonin and demonstrate that it has the characteristics of a secreted protein.

Fish calcitonin genes: primitive bony fish genes have been conserved in some lower vertebrates

Using the polymerase chain reaction method, we amplified calcitonin genes from the cDNA of the ultimobranchial glands or from the genomic DNA of the blood cells and liver of various fishes. The fishes examined were primitive bony fishes (lungfish, polypterus, sturgeon, and gar), 16 species of teleosts, and cartilaginous fishes (stingray). Sequenced calcitonin genes were compared among fishes and with those of reptiles and chickens. The similarity of the calcitonin genes was the highest between the reptile and chicken groups and the primitive bony fishes (sequence similarity of the nucleotides 81-90%). The values between teleosts and the primitive bony fishes were 70-81%, with the exception of eels. Eel calcitonin genes were very similar to those of primitive bony fishes (83-88%). Stingray calcitonin genes were relatively more similar to those of the primitive bony fishes (74-78%) than to teleosts (63-73%). In goldfish and sardine, two types of calcitonin genes were found. We concluded that the genes of primitive bony fish are placed at a fundamental position in this hormone, at least among these vertebrates.

Identification of a new calcitonin gene in the salmon Oncorhynchus gorbuscha

Three isoforms of calcitonin (CT) exist in salmonids. Isohormones I and II are expressed in the pink salmon Oncorhynchus gorbuscha. We report here the existence in this species of a CT gene and of its transcripts, which encode for a fourth isohormone, the salmon CT (sCT) IV. This new CT gene was identified by PCR from genomic DNA and by sequencing the amplified DNA. The expression of this CT gene was established in ultimobranchial body and brain, by reverse transcription-PCR, hybridization and sequencing. The sCT IV gene, like the sCT I gene, is a complex transcription unit, containing exons encoding for a CT as a calcitonin gene-related peptide (CGRP) molecule. The predicted peptide, sCT IV, has a greater homology with the eel CT and the sCT II than with the sCT I. Alignment of the sCT IV with other fish and chicken CT showed amino acid modifications in similar positions as those found during evolution. The predicted salmon CGRP IV peptide is highly homologous to the known CGRP molecules in other species, confirming the high conservation of the molecule during evolution. This identification of a new salmon CT gene is interesting both for the therapeutic potential represented by the new molecules encoded by this gene and for phylogenetic studies.

Production of salmon calcitonin I in Oncorhynchus gorbuscha by alternative polyadenylation of two RNA species

RNAs of ultimobranchial bodies (U.B.) from the pink salmon, Oncorhynchus gorbuscha, were studied using the polymerase chain reaction (PCR) with specific oligodeoxyribonucleotides (oligos) of the salmon calcitonin (sCT) mRNA selected in exon 2 or 3 and a poly(T) oligo. We observed two amplified DNA fragments, differing by 200 bp which hybridized with a specific exon 4 probe. Sequence analysis indicated that they both encoded exon 4, but differed in the length of their 3' non-coding regions by use of a putative polyadenylation signal situated 200 bp upstream from the established polyadenylation site. These two polyadenylation signals very likely were regulated differently, as the larger expressed transcript was predominant. To date, such use of an alternative polyadenylation signal in a CT mRNA has not been described in other vertebrates, and only the chicken CT mRNA possesses a second classical polyadenylation signal which is not known to be used. This characteristic of sCT biosynthesis appears to be typical in lower vertebrates and is of phylogenic interest. Moreover, it engenders a hypothesis of a relationship between the high concentration of the peptide observed in females of this species and their capacity to produce sCT by different biosynthetic pathways.

The calcitonin gene is expressed in salmon gills

Calcitonin is an important physiological regulator of salmon gills. Although the calcitonin receptor was found in salmon gills, the critical question concerning the source of the hormone remained unanswered. In this communication, evidence is presented for expression of calcitonin mRNA and its encoded peptide in gills of the pink salmon, Oncorhynchus gorbuscha. The expression of calcitonin gene transcripts was demonstrated by reverse transcription-polymerase chain reaction, Southern hybridization, and sequencing. The sequencing identified a sequence corresponding to that of exon 4 of the salmon calcitonin gene. Expression of the encoded calcitonin gene in gills was detected by radioimmunoassay in gill extracts. This synthesis of calcitonin in gills, which also possess specific receptors to the peptide, suggests function of an autocrine or paracrine process producing calcitonin in this tissue. These observations confirm and extend previous reports on the physiological role of calcitonin in fish gills.

Processing of a fusion protein by endoprotease in COS-1 cells for secretion of mature peptide by using a chimeric expression vector

The subtilisin-related proprotein convertase furin is expressed in various mammalian tissues. Expecting that COS-1 cells have a furin-like endoprotease, we constructed a fusion expression vector for production of a recombinant foreign protein having no signal peptide or a protein in truncated form into secreted mature protein. A cDNA fragment encoding N-terminal procalcitonin (pro-CT) of human calcitonin precursor was inserted into the mammalian expression vector pME18S. We used PCR techniques to generate four kinds of cDNAs encoding the C terminus of the pro-CT with Arg residues at P4 (Arg-Xaa-Lys-Arg), P6 (Arg-Xaa-Xaa-Xaa-Lys-Arg), or both (Arg-Xaa-Arg-Xaa-Lys-Arg), in addition to the Lys-Arg motif at the cleavage site, in order to determine the conditions for efficient processing in nonendocrine cells, such as COS-1 cells. The cDNA coding for the Fc fragment of human immunoglobulin G1 was fused in-frame to the cDNA encoding pro-CT at its C terminus. Upon transfection of the chimeric plasmids into COS-1 cells, almost all of the fusion protein with the Arg residues at both P4 and P6 were processed into secreted Fc product, even without cotransfection of furin. These results indicate that COS-1 cells have a furin-like endoprotease and suggest that pro-CT, with the Arg residues at both P4 and P6, can be used as a carrier peptide for expression of a foreign protein having no signal peptide or a protein in truncated form in COS-1 cells.

Identification and partial characterization of the salmon calcitonin/CGRP gene by polymerase chain reaction

The polymerase chain reaction was used to amplify sequences encoding calcitonin and CGRP in the genomic DNA of salmon. Amplification products of the expected length were cloned and sequenced. In this way a new CGRP-coding sequence was identified. The new sequence and the known salmon calcitonin-coding sequence were shown to be part of one gene, implying that alternative gene expression takes place in fish.

Expression of the calcitonin gene during migration of the Pacific salmon, Oncorhynchus gorbuscha

Plasma calcitonin levels increase during reproduction in female salmon. Whether these changes in circulating levels of the hormone are due to increased secretion and or increased biosynthesis is not established. We measured total and poly A+ RNAs and calcitonin content of ultimobranchial bodies of male and female pink salmon during the different stages of the reproductive cycle. Calcitonin mRNAs were analysed by hybridization of northern and dot blots with a specific probe for salmon calcitonin. Dot blot autoradiography indicated that female animals had higher levels of CT mRNA than males and these values were correlated with plasma calcitonin levels. In conclusion, sexual hormones still to be identified, are probably implicated in the expression of the calcitonin gene in females during the reproductive cycle.

Is helodermin-like immunoreactivity in human thyroid C cells due to a salmon calcitonin-like substance?

Helodermin-like and salmon calcitonin (sCT)-like immunoreactivities co-existed in a subset of human calcitonin (hCT)-containing cells in normal human thyroid tissue and medullary thyroid carcinomas. Helodermin/sCT-immunoreactive cells were mostly different from calcitonin gene-related peptide (CGRP)-positive cells. Helodermin and sCT immunoreactivities were not identified in pulmonary and pancreatic hCT-positive neuroendocrine tumors, except for a few lung tumor cells showing positive staining with one of two sCT antisera used. Helodermin immunoreactivity demonstrated by rabbit antiserum R0086 was completely abolished in the presence of synthetic sCT, while sCT immunoreactivity was not absorbed by synthetic helodermin. The carboxyl terminal Arg30-Thr31 sequence (and Pro35 amide structure) of helodermin would be the epitopic site recognized by this antiserum, since a similar amino acid sequence is present in sCT molecules but absent from hCT and CGRP.

Predicted structure of rabbit N-terminal, calcitonin and katacalcin peptides

Poly A rich RNA was extracted from rabbit thyroid and cDNA obtained by the action of reverse transcriptase. The cDNA was used to construct a library in lambda GT 11. Screening of the library with a radio-labelled probe specific for human calcitonin allowed the isolation of a clone containing an open reading frame with a high homology with human and murine exon 4 of calcitonin/calcitonin gene-related peptide gene. This sequence codes for a typical calcitonin precursor. We deduced the amino acid sequence of rabbit N-terminal peptide, calcitonin and katacalcin.

The calcitonin gene peptides: biology and clinical relevance

The calcitonin/CGRP multigene complex encodes a family of peptides: calcitonin, its C-terminal flanking peptide, katacalcin, and a third novel peptide, calcitonin gene-related peptide (CGRP). The 32-amino acid peptide calcitonin inhibits the osteoclast, thereby conserving skeletal mass during periods of potential calcium lack, such as pregnancy, growth, and lactation. This hormonal role is emphasized by observations that lower circulating calcitonin levels are associated with bone loss and that calcitonin replacement prevents further bone loss. Structurally, CGRP resembles calcitonin and has been implicated in neuromodulation and in the physiological regulation of blood flow. Here we review the molecular genetics, structure, and function of the calcitonin-gene peptides as analyzed in the laboratory and focus on more recent clinical studies relating to disorders and therapeutics.

A third human CALC (pseudo)gene on chromosome 11

A genomic locus in man (CALC-III) containing nucleotide sequences highly homologous to both exon 2 and exon 3 of the CALC-I and -II genes, is described in this paper. The CALC-I gene produces calcitonin (CT) (encoded by exon 4) or calcitonin gene-related peptide (CGRP) (encoded by exon 5) in a tissue-specific fashion. The CALC-II gene produces a second human CGRP, but probably not a second CT. The CALC-III gene does not seem to encode a CT- or CGRP-related polypeptide hormone and is probably a pseudogene. Like the other two CALC genes, the CALC-III gene is located on human chromosome 11.