Antiapoptotic function of Bcl-2 in mast cells is dependent on its association with heat shock protein 90β

Abstract

In the present study, we demonstrated that the antiapoptotic function of Bcl-2 in mast cells is significantly dependent on its association with the heat shock protein 90␤ (Hsp90␤). Dissociation of these 2 proteins inhibits the antiapoptotic activity of Bcl-2 by initiating the release of cytochrome c from mitochondria into cytosol and increasing the activity of caspase 3 and caspase 7, resulting in mast-cell apoptosis. The antiapoptotic activity of Bcl-2 was greatly affected by knocking-out specifically Hsp90␤ using the RNA interference approach. Thus, for the first time, it has been shown that Hsp90␤ might modulate the antiapoptotic activity of Bcl-2 at least in mast cells. These find- IntroductionMast cells, the major cellular players in allergy, have been found to exist at a constant number in tissues under normal conditions. This probably reflects an equilibrium between cell migration, proliferation, and apoptosis. 1,2 The biochemical events leading to apoptosis in this cell type have just started to be explored. 2,3 We recently demonstrated the role of Bcl-2 in the prevention of mast-cell apoptosis using a novel antibody originated from phage display library. 4 We constructed an anti-Bcl-2 singlechain Fv connected to 11 amino acids derived from TAT protein, which enabled the antibody to penetrate the cell membrane. The anti-Bcl-2 antibody bound specifically to endogenous Bcl-2, leading to the initiation of the apoptosis cascade. 4 The Bcl2 gene family encodes a series of proteins involved in the regulation of programmed cell death. 5 Members of the family can be grouped into 2 distinct sets with antagonistic functions. Bcl-2, BclX L , Mcl-1, and A1/Bfl-1 have antiapoptotic, protective functions and prevent the activation of downstream death-effector caspase proteases. In contrast, proteins such as Bax, Bak, Bad, and Bid have proapoptotic roles and can antagonize the cell-protective functions of Bcl-2. 5,6 Although it is not fully understood how Bcl-2 family proteins regulate apoptotic pathways, one possible mechanism is that members of this family engage in various protein-protein interactions to form homotypic and heterotypic dimers important for their biologic functions. 7,8 Association of Bcl-2 with other antiapoptotic proteins through Bcl-2 homology (BH) domains prevents changes in mitochondrial membrane potential (⌬⌿ m ) and the release of cytochrome c from mitochondria. 9 The ability of many Bcl-2 family members to form homodimers and heterodimers through their BH domains is important for the activation of specific functions, such as initiating and altering the process of apoptosis and neutralizing these functions in the cells. 10 It was, therefore, postulated that the relative ratio of antiapoptotic to proapoptotic dimers plays a pivotal role in determining the resistance of a cell to apoptosis. However, the function of Bcl-2 has been found to be affected by its association with proteins not belonging to the Bcl-2 family. Recently, it was observed that Bcl-2 is able to act as a "cell-killer" on bindi...

Selective depletion of alloreactive T cells by targeted therapy of heat shock protein 90: a novel strategy for control of graft-versus-host disease

“…The molecular chaperone Hsp90 has been shown to stabilize many key signaling intermediates 8 and to exert antiapoptotic effects in various cell types, [13][14][15] strongly suggesting a similar function in primary human T lymphocytes. First, we addressed the question as to whether expression of both Hsp90 isoforms ␣ and ␤ in T lymphocytes is activation-dependent as in other cell types.…”

Inhibition of HSP90 by AUY922 Preferentially Kills Mutant KRAS Colon Cancer Cells by Activating Bim through ER Stress

“…This is frequently mediated by activation of the mitochondrial apoptotic pathway, which is regulated by the balance between proapoptotic and antiapoptotic Bcl-2 family proteins (8). Of note, multiple Bcl-2 family proteins are responsive to inhibition of HSP90 in a cell-type and context-dependent manner (9)(10)(11)(12). In particular, p53-dependent induction of the BH3-only protein PUMA has been shown to be responsible for apoptosis of colon cancer cells induced by the HSP90 inhibitor 17-AAG (10).…”

“…In particular, p53-dependent induction of the BH3-only protein PUMA has been shown to be responsible for apoptosis of colon cancer cells induced by the HSP90 inhibitor 17-AAG (10). Moreover, the antiapoptotic Bcl-2 family proteins, Bcl-2, Mcl-1, and Bcl-XL, have all been reported to protect cells against HSP90 inhibitioninduced apoptosis (9,(11)(12)(13).…”

Heat shock proteins (HSP)-60, -70, -90, and 105 display variable spatial and temporal immunolocalization patterns in the involuting rat uterus

“…In the literature, there were few reports on the expression of HSPs in mast cells (MCs) (Cohen-Saidon et al, 2006;Shabelnikov et al, 2012), and no information was reported regarding the expression of HSPs in the uterine MCs. Consequently the expression and functions of HSPs in uterine mast cells are unknown.…”