Disruption of the Complex between GAPDH and Hsp70 Sensitizes C6 Glioblastoma Cells to Hypoxic Stress

Abstract

Hypoxia, which commonly accompanies tumor growth, depending on its strength may cause the enhancement of tumorigenicity of cancer cells or their death. One of the proteins targeted by hypoxia is glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and we demonstrated here that hypoxia mimicked by treating C6 rat glioblastoma cells with cobalt chloride caused an up-regulation of the enzyme expression, while further elevation of hypoxic stress caused the enzyme aggregation concomitantly with cell death. Reduction or elevation of GAPDH performed with the aid of specific shRNAs resulted in the augmentation of the tumorigenicity of C6 cells or their sensitization to hypoxic stress. Another hypoxia-regulated protein, Hsp70 chaperone, was shown to prevent the aggregation of oxidized GAPDH and to reduce hypoxia-mediated cell death. In order to release the enzyme molecules from the chaperone, we employed its inhibitor, derivative of colchicine. The compound was found to substantially increase aggregation of GAPDH and to sensitize C6 cells to hypoxia both in vitro and in animals bearing tumors with distinct levels of the enzyme expression. In conclusion, blocking the chaperonic activity of Hsp70 and its interaction with GAPDH may become a promising strategy to overcome tumor resistance to multiple environmental stresses and enhance existing therapeutic tools.

3-Bromo-Isoxazoline Derivatives Inhibit GAPDH Enzyme in PDAC Cells Triggering Autophagy and Apoptotic Cell Death

“…Unlike other covalent modifications at the catalytic cysteine, including oxidation and S-nitrosylation [23], we have previously ruled out that the covalent binding of 3-bromo-isoxazoline derivatives affects the stability and integrity of the GAPDH tetramer [12]. Therefore, we envisage that the main mechanism of cytotoxicity resides in the inhibition of glycolysis rather than in GAPDH aggregation, a mechanism that was associated with cell death in glioblastoma cells [24].…”

2-Methoxyestradiol Damages DNA in Glioblastoma Cells by Regulating nNOS and Heat Shock Proteins

“…Intriguingly, 2-ME did not affect HSP70 expression in 143B osteosarcoma cells [ 80 ] or in A375 melanoma cells [ 37 ]. HSP70 was shown to prevent the aggregation of oxidized glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and to diminish cell death induced by hypoxia [ 81 ]. The overexpression of HSP70 supports the ubiquitination and proteasomal degradation of nNOS [ 82 ], while its inhibition sensitizes cancer cells to apoptosis [ 83 ].…”

“…The overexpression of HSP70 supports the ubiquitination and proteasomal degradation of nNOS [ 82 ], while its inhibition sensitizes cancer cells to apoptosis [ 83 ]. Delaying the function of Hsp70 and its interaction with GAPDH may contribute to rendering tumors receptive to chemotherapy and resistant to a variety of environmental stressors [ 81 ].…”

HSP70 Family in Cancer: Signaling Mechanisms and Therapeutic Advances

“…While under conditions of hypoxia, the antitumor effect of AEAC in glioblastoma was enhanced through disrupting PPI between HSP70 and GAPDH to promote the aggregation of oxidized GAPDH. Additionally, cells with high expression of GAPDH were more sensitive to AEAC than those with normal expression of GAPDH [ 143 ]. By disrupting the HSP70-caspase 3 complex, a derivative of benzodioxol (BT44) increased sensitivity of colon cancer and lymphoma cells to apoptosis [ 144 ].…”