title: The growth hormone dependent serine protease inhibitor, Spi 2.1 inhibits the des (1-3) insulin-like growth factor-I generating protease.
abstract: The conversion of insulin-like growth factor-I (IGF-I) to the biologically more active des (1-3) IGF-I variant is catalyzed by a ubiquitous protease. This proteolytic activity is inhibited by human alpha1-antitrypsin and soy-bean trypsin inhibitor and is up-regulated in serum and tissue extracts of hypophysectomized rats. These observations lead us to investigate whether the growth hormone regulated, serine protease inhibitor, Spi 2.1 was able to inhibit the des (1-3) IGF-I generating protease. Dihydrofolate reductase deficient Chinese hamster ovary (CHO(dhfr-ve)) cells were transfected with a rat Spi 2.1 expression vector containing the dhfr and neomycin resistance gene. Stable transfectants were selected using G418 and amplified using methotrexate. Conditioned medium from Spi 2.1 transfected CHO cells potently inhibited proteolytic activity directed against a synthetic hexa-peptide with a sequence identical to the N-terminal of IGF-I. In contrast conditioned medium from wild-type CHO cells had little effect. Based upon these observations we suggest that our previous finding of enhanced des (1-3) IGF-I generating protease activity in growth hormone deficient rats may be, at least partly explained by reduced levels of Spi 2.1. Furthermore, we propose that the regulation of the generation of des (1-3) IGF-I may be an additional potential site of growth hormone regulation of IGF-I action.
authors.affiliation: Department of Internal Medicine, University of Manitoba, Winnipeg, Canada.
authors.forename: C
authors.initials: C
authors.lastname: Maake
authors.forename: H
authors.initials: H
authors.lastname: Yamamoto
authors.forename: L J
authors.initials: LJ
authors.lastname: Murphy
mesh_terms: D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D010450:Endopeptidases / Q000187:drug effects / Q000378:metabolism*; D013006:Growth Hormone / Q000502:physiology*; D007334:Insulin-Like Growth Factor I / Q000096:biosynthesis*; D009687:Nuclear Proteins / Q000494:pharmacology*; D010446:Peptide Fragments / Q000096:biosynthesis*; D051381:Rats; D011994:Recombinant Proteins / Q000494:pharmacology; D015842:Serine Proteinase Inhibitors / Q000494:pharmacology*; D013194:Staining and Labeling
chemical_list: C091103:LOC299282 protein, rat; D009687:Nuclear Proteins; D010446:Peptide Fragments; D011994:Recombinant Proteins; D015842:Serine Proteinase Inhibitors; C058957:insulin-like growth factor 1, des-(1-3)-; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone; D010450:Endopeptidases