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 been reported that intracellular Akt is a client protein of HSP90 that forms complexes in which Akt is stabilized and rendered functionally active . Results of our previous work supported the proposal that the angiogenic effect of Grp94-IgG is mediated by autocrine–paracrine mechanisms of activation of HSP90 and HSP70 . Thus, if CTT was able to inhibit the Grp94-IgG dependent activation of the PI3K/Akt pathway by positively targeting the same pathway, one might expect that the HSP90 expression were similarly affected. To investigate this issue, we performed immunofluorescence experiments with both anti-HSP90 and anti-HSP70 Abs on HUVECs treated with Grp94-IgG and CTT at 10 μM, both alone and together. In the former experiment, Grp94-IgG induced the appearance of numerous podosomes in HUVECs in which the HSP90-related fluorescence concentrated mostly in association with actin (Fig. 3, panels b), to testify the intense cytoskeleton modification accompanying proliferation and angiogenic transformation of cells. CTT at 10 μM led to a significant reduction in both the podosomes number and HSP90-dependent fluorescence sustained by Grp94-IgG, although it did not antagonize completely this effect, and HSP90 expression appeared to be still increased with respect to the control (Fig. 3, panels d). CTT alone was as effective as Grp94-IgG in stimulating the podosome formation and in inducing the expression of HSP90 (Fig. 3, panels c), a result that fit both the morphological alteration and stimulation of Akt observed with CTT alone. The results also pointed to the close molecular link between activation of the Akt pathway and increased expression of HSP90 in the cell membrane, as predicted by the function of HSP90 in remodelling the actin cytoskeleton during cell differentiation and migration .
Affiliation: Department of Pharmacology and Anesthesiology, University of Padova, Largo E. Meneghetti, Padova, Italy.