A non-calcitonin secretory peptide derived from preprocalcitonin

Ctriporin, a new anti-methicillin-resistant Staphylococcus aureus peptide from the venom of the scorpion Chaerilus tricostatus

Antibiotic-resistant microbes, such as methicillin-resistant Staphylococcus aureus, seriously threaten human health. The outbreak of "superbugs" in recent years emphasizes once again the need for the development of new antimicrobial agents or resources. Antimicrobial peptides have an evident bactericidal effect against multidrug-resistant pathogens. In the present study, a new antimicrobial peptide, ctriporin, was cloned and characterized from the venom of the scorpion Chaerilus tricostatus, an animal which has not yet been explored for toxic peptide resources. The MICs of ctriporin against Staphylococcus aureus, Bacillus thuringiensis, Bacillus subtilis, Micrococcus luteus, and Candida albicans are 5 to 20 μg/ml. Meanwhile, it MIC against clinical antibiotic-resistant bacterial strains is 10 μg/ml. Furthermore, the potential for ctriporin to be used as a topical antibiotic for treating staphylococcal skin infections was investigated. External use of the peptide ctriporin dramatically decreased the bacterial counts and cured skin infections in mice. In addition, ctriporin demonstrates antimicrobial efficacy via the bactericidal mechanism of rapid cell lysis. Together, these results suggest the potential of developing ctriporin as a new topical antibiotic.

Cloning of a cDNA encoding sheep calcitonin from a thyroid C-cell library

A sheep thyroid C-cell cDNA library constructed in lambda ZAPII was screened with a probe specific for the human calcitonin (CT)-encoding gene (CT). Plaque lifts from a total of 6 x 10(4) recombinant plaques identified six overlapping cDNA clones, one of which was an 806-bp cDNA representing an almost full-length copy of the sheep CT mRNA. The nucleotide (nt) sequence consists of a 71-bp 5'-flanking sequence, a protein-coding region of 429 bp with a coding potential for a 143-amino-acid (aa) protein with a deduced M(r) of 15,888 and a 306-bp 3'-untranslated region. Northern blot analysis of sheep thyroid tissue revealed two major mRNAs with sizes of 0.9 and 0.65 kb. The sheep CT cDNA shows 71% similarity at the nt level to human CT and 58% identity at the predicted aa level.

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.

Determination of circulating monomeric katacalcin and calcitonin: physiological studies in normal subjects

Katacalcin is a recently discovered peptide, contained within the calcitonin precursor. For the highly sensitive radioimmunological measurement of katacalcin and calcitonin we used extraction on C-18, thereby lowering the detection limits in serum to 0.8 pmol/l (katacalcin) and 0.7 pmol/l (calcitonin), and simultaneously improving the specificities of both assays for the monomeric forms of the peptides. Extraction recoveries were greater than 96% and greater than 95% for pure monoiodinated [125I]Tyr(0)-katacalcin and [125I]calcitonin, respectively; and 95-98% and 91-97% respectively for the corresponding unlabelled peptides. This method is sufficiently sensitive and specific for studies on the physiology of both peptides. Gel filtration of serum from a patient with medullary carcinoma of the thyroid showed that the majority of high molecular weight forms of katacalcin and calcitonin did not bind to C-18, and that the eluted material consisted to more than 90% of monomeric katacalcin and calcitonin. Basal levels (mean +/- SEM) of katacalcin were higher in men (3.0 +/- 0.6 pmol/l, age less than 40 years, and 1.8 +/- 0.4 pmol/l, age greater than 40 years) and younger women (2.1 +/- 0.4 pmol/l) than in older women (1.3 +/- 0.6 pmol/l; p less than 0.02). The respective values for calcitonin were 5.1 +/- 0.9 and 4.0 +/- 0.6 pmol/l for young and older men, and 2.3 +/- 0.4 and 2.8 +/- 0.8 pmol/l for young and older women, with a significant sex-related difference in both age groups. Basal serum levels of katacalcin and calcitonin were highly correlated (katacalcin = 0.66 calcitonin -0.12 pmol/l; p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Identification of cellular prosomatostatin and nonsomatostatin peptides derived from its amino terminus

Rat prosomatostatin was isolated from a somatostatin-producing cell line and was partially microsequenced. This indicated the amino terminal structure of cellular prosomatostatin and implied a 92-amino acid sequence for the somatostatin precursor. Based on the structure for cellular prosomatostatin, a peptide was synthesized and used to develop a radioimmunoassay directed toward the amino terminal portion of prosomatostatin. This assay has revealed two peptides containing the amino-terminal portion of prosomatostatin in a somatostatin-secreting CA-77 rat medullary thyroid carcinoma cell line. These two peptides - MW 4000 and 8000 daltons - lack somatostatin immunoreactivity. Thus, processing of prosomatostatin occurs both at the amino and carboxyl regions. These results open the way for elucidation of the structure, function and metabolism of non-somatostatin peptides derived from the amino terminus of prosomatostatin.

Multiple endocrine neoplasia syndromes

The multiple endocrine neoplasia (MEN) syndromes are characterized by autosomal dominant inheritance with a high degree of penetrance but varying expression. This review gives a classification of these syndromes and a short summary of the historical background. The pathogenesis of the disease and its possible origin in the APUD cell system are discussed together with the mechanisms underlying normal and ectopic hormone production by MEN tumors on the basis of recent findings in molecular endocrinology. The natural history and the clinical manifestations of the different syndromes are described. The sensitivity and discriminative capacity of the tests used to detect the syndromes in an early stage are compared. The choice of therapy and criteria for the timing and extensiveness of treatment are also considered. Lastly, problems associated with the ethical and legal aspects of screening, central registration, and monitoring of relatives at risk are described.

Alternative RNA processing in calcitonin gene expression generates mRNAs encoding different polypeptide products

Alternative processing of RNA transcripts from the calcitonin gene results in the production of distinct mRNAs encoding the hormone calcitonin or a predicted product referred to as calcitonin gene-related peptide (CGRP). The calcitonin mRNA predominates in the thyroid while the CGRP-specific mRNA appears to predominate in the hypothalamus. These observations lead us to propose a model in which developmental regulation of RNA processing is used to increase the diversity of neuroendocrine gene expression.