title: Effects of mutated pregnancy-associated plasma protein-a on atherosclerotic lesion development in mice.
abstract: Pregnancy-associated plasma protein-A (PAPP-A) is a large multidomain metalloprotease involved in cleavage of IGF binding protein (IGFBP)-4 and -5 thereby causing release of bioactive IGF. Individual domains of PAPP-A have been characterized in vitro, including the metzincin proteolytic domain important for IGFBP proteolytic activity, short consensus repeats critical for cell surface association, and Lin-12/Notch repeat module demonstrated to determine IGFBP substrate specificity. To test the hypothesis that specific cleavage of IGFBP-4 by PAPP-A in close proximity to the cell surface is required for development of lesions in a murine model of atherosclerosis, the following PAPP-A transgenic (Tg) mice were generated: Tg(E483A), which lacks all PAPP-A proteolytic activity; Tg(D1499A), which selectively lacks proteolytic activity against IGFBP-4; and Tg(K1296A/K1316A), in which cell surface binding is compromised. Following cross-breeding with apolipoprotein E (ApoE) knockout (KO) mice, ApoE KO/Tg mice were fed a high-fat diet to promote aortic lesion development. Lesion area was increased 2-fold in aortas from ApoE KO/Tg wild-type compared with ApoE KO mice (P < 0.001). However, there was no significant increase in the lesion area in any of the ApoE KO/Tg mutant mice. We conclude that PAPP-A proteolytic activity is required for the lesion-promoting effect of PAPP-A and that its specificity must be directed against IGFBP-4. Furthermore, our data demonstrate that cleavage of IGFBP-4 at a distance from the cell surface, and hence from the IGF receptor, is not effective in promoting the development of the atherosclerotic lesions. Thus, PAPP-A exerts its effect while bound to the cell surface in vivo.
authors.affiliation: Division of Endocrinology and Metabolism, Mayo Clinic, Rochester, MN 55905, USA.
authors.forename: Henning B
authors.initials: HB
authors.lastname: Boldt
authors.forename: Laurie K
authors.initials: LK
authors.lastname: Bale
authors.forename: Zachary T
authors.initials: ZT
authors.lastname: Resch
authors.forename: Claus
authors.initials: C
authors.lastname: Oxvig
authors.forename: Michael T
authors.initials: MT
authors.lastname: Overgaard
authors.forename: Cheryl A
authors.initials: CA
authors.lastname: Conover
mesh_terms: D000818:Animals; D001011:Aorta / Q000166:cytology; D001057:Apolipoproteins E / Q000235:genetics / Q000378:metabolism; D050197:Atherosclerosis / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D018974:Insulin-Like Growth Factor Binding Protein 4 / Q000378:metabolism; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D032389:Myocytes, Smooth Muscle / Q000378:metabolism; D011266:Pregnancy-Associated Plasma Protein-A / Q000235:genetics / Q000378:metabolism*
chemical_list: D001057:Apolipoproteins E; D018974:Insulin-Like Growth Factor Binding Protein 4; D011266:Pregnancy-Associated Plasma Protein-A