title: Crucial role of HSP90 in the Akt-dependent promotion of angiogenic-like effect of glucose-regulated protein94 (Grp94)-IgG complexes.
abstract: Previous observations showed that complexes of glucose-regulated protein94 (Grp94) with human IgG, both those isolated from plasma of diabetic subjects and complexes formed in vitro, displayed cytokine-like effects on human umbilical vein endothelial cells (HUVECs), including angiogenic-like transformation capacity that predicted an increased risk of vascular damage. The aim of the present work was to find an effective inhibitor of the angiogenic-like effect of Grp94-IgG complexes. Because this effect is mediated by an increased expression of matrix metalloprotease-9 (MMP-9), we tested the selective MMP-9 inhibitor, the cyclic decapeptide CTT (CTTHWGFTLC) at 5, 10 and 20 μM. CCT failed to inhibit any morphological alteration induced by Grp94-IgG on HUVECs, on its own displaying a paradoxical angiogenic-like activity. We identified the phosphatidylinositol 3-kinase (PI3K)/Akt pathway as the specific target activated by both Grp94-IgG and CTT for sustaining the angiogenic-like transformation of HUVECs. Functioning of the PI3K/Akt pathway was crucially dependent on functional heat-shock protein (HSP)90, and both Grp94-IgG and CTT caused and increased expression of HSP90, promoting its localization to podosomes. CTT appeared to enhance the angiogenic-like effect of Grp94-IgG by increasing the rate of secretion of both HSP90 and MMP-9. By preventing the chaperoning capacity of HSP90 with the inhibitor purine-scaffold (PU)-H71 that blocked the ATP-binding site on HSP90, it was possible to inhibit the expression of Akt and secretion of HSP90 and MMP-9 induced by Grp94-IgG, thus completely reversing the angiogenic pattern. Results reveal a fundamental role of HSP90 in the PI3K/Akt pathway-mediated angiogenic-like effect of Grp94-IgG, also questioning the capacity of CTT to serve as an effective inhibitor of the angiogenic effect.
authors.affiliation: Department of Pharmacology and Anesthesiology, University of Padova, Largo E. Meneghetti, Padova, Italy.
authors.forename: Elisa
authors.initials: E
authors.lastname: Tramentozzi
authors.forename: Elena
authors.initials: E
authors.lastname: Tibaldi
authors.forename: Anna Maria
authors.initials: AM
authors.lastname: Brunati
authors.forename: Andrea
authors.initials: A
authors.lastname: Pagetta
authors.forename: Paola
authors.initials: P
authors.lastname: Finotti
mesh_terms: D049109:Cell Proliferation; D002478:Cells, Cultured; D005455:Fluorescent Antibody Technique; D018841:HSP90 Heat-Shock Proteins / Q000378:metabolism*; D061307:Human Umbilical Vein Endothelial Cells / Q000378:metabolism*; D006801:Humans; D007074:Immunoglobulin G / Q000378:metabolism*; D020780:Matrix Metalloproteinase 9; D008562:Membrane Glycoproteins / Q000378:metabolism*; D018919:Neovascularization, Physiologic; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D018841:HSP90 Heat-Shock Proteins; D007074:Immunoglobulin G; D008562:Membrane Glycoproteins; C053387:endoplasmin; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D020780:Matrix Metalloproteinase 9