Crucial role of HSP90 in the Akt-dependent promotion of angiogenic-like effect of glucose-regulated protein94 (Grp94)-IgG complexes.
Bottom Line: CCT failed to inhibit any morphological alteration induced by Grp94-IgG on HUVECs, on its own displaying a paradoxical angiogenic-like activity.CTT appeared to enhance the angiogenic-like effect of Grp94-IgG by increasing the rate of secretion of both HSP90 and MMP-9.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.
Affiliation: Department of Pharmacology and Anesthesiology, University of Padova, Largo E. Meneghetti, Padova, Italy.Show MeSH
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Mentions: It has firmly been established that mitogenic stimuli that promote cell proliferation and differentiation also lead to an increased expression of MMP-9 , and that MMP-9 expressed by endothelial cells is critical for inducing angiogenesis [6, 12]. However, mechanisms by which MMP-9 might contribute to the development and progression of angiogenesis are still controversial, although it appears to be for most part independent of MMP-9 proteolytic activity [10, 11, 24]. Despite the intensive effort spent in this direction, the signal transduction pathway(s) specifically involved in regulating the expression of MMP-9 following application of various stimuli has not been identified with precision. While the phosphorylation of ERK1/2 appears to be not sufficient for the expression of MMP-9 , the role of activated PI3K/Akt pathway in driving stimulation of MMP-9 production and secretion [8, 25] has been considered with much higher relevance. In immunoblotting experiments with monoclonal anti-MMP-9 Abs on whole lysates of HUVECs treated with Grp94-IgG, with and without CTT, we were unable to measure the expression of MMP-9, whereas the inactive (94 kD) form of MMP-9 was detected in gel zymography experiments on culture media, to testify active secretion. Much less intense and of variable intensity was the digestion band referred to the active form of MMP-9 at 92 kD. The MMP-9 pro-form underwent an intense stimulation with both Grp94-IgG and CTT alone (Fig. 5). Again, when tested together, CTT did not reverse at all the stimulation sustained by Grp94-IgG, causing instead a further increase in the area of the digestion band of MMP-9 pro-form that is activated experimentally by zymography. The results are in accord with those reported above, supporting the possibility that the synergic stimulation of the PI3K/Akt pathway by Grp94-IgG and CTT can also mediate the increase in MMP-9 pro-form expression and secretion.
Affiliation: Department of Pharmacology and Anesthesiology, University of Padova, Largo E. Meneghetti, Padova, Italy.