title: Processing-independent radioimmunoanalysis: a general analytical principle applied to progastrin and its products.
abstract: Most peptide hormone assays measure only fully processed bioactive peptides. Such assays are unsuited to detect hormone gene expression by alternative or attenuated prohormone processing (tissue- or cell-specific processing). The gastrin system is expressed in several different tissues and is therefore useful for studies of tissue-specific processing. Consequently we have developed a simple processing-independent radioimmunoanalysis for progastrin. Using antisera against the NH2-terminus of a sequence, devoid of processing sites (preprogastrin76-86) after trypsination of neighboring cleavage sites, the assay quantitates the mRNA product irrespective of degree of processing. Used together with a conventional assay for the mature carboxyamidated gastrins, the processing-independent analysis shows that in different tissues only 1 to 55% of the total translation product is processed to bioactive gastrins. Thus processing-independent analysis greatly improves the detection of gastrin gene expression at the peptide level. The principle of the assay should be applicable to all protein and peptide systems.
authors.affiliation: University Department of Gastroenterology C, Rigshospitalet, Copenhagen, Denmark.
authors.forename: L
authors.initials: L
authors.lastname: Bardram
authors.forename: J F
authors.initials: JF
authors.lastname: Rehfeld
mesh_terms: D000595:Amino Acid Sequence; D002850:Chromatography, Gel; D005753:Gastric Mucosa / Q000032:analysis; D015408:Gastrinoma / Q000032:analysis; D005755:Gastrins / Q000032:analysis* / Q000235:genetics; D006801:Humans; D008175:Lung Neoplasms / Q000032:analysis; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000032:analysis; D011498:Protein Precursors / Q000032:analysis* / Q000235:genetics; D011499:Protein Processing, Post-Translational; D011863:Radioimmunoassay / Q000379:methods*; D014357:Trypsin
chemical_list: D005755:Gastrins; D010446:Peptide Fragments; D011498:Protein Precursors; C013706:big gastrin; D014357:Trypsin