Heat Shock Protein 90 Stabilization of ErbB2 Expression Is Disrupted by ATP Depletion in Myocytes

Abstract

Heat shock protein (Hsp) 90 is a ubiquitously expressed chaperone that stabilizes expression of multiple signaling kinases involved in growth regulation, including ErbB2, Raf-1, and Akt. The chaperone activity of Hsp90 requires ATP, which binds with ϳ10-fold lower affinity than ADP. This suggests that Hsp90 may be a physiological ATP sensor, regulating the stability of growth signaling cascades in relation to cellular energy charge. Here we show that lowering ATP concentration by inhibiting glycolysis or mitochondrial respiration in isolated myocytes triggers rapid dissociation of Hsp90 from ErbB2 and degradation of ErbB2 along with other client proteins. The effect of disrupting Hsp90 chaperone activity by ATP depletion was similar to the effect of the pharmacological Hsp90 inhibitor geldanamycin. ATP depletion-induced disruption of Hsp90 chaperone activity was associated with cellular resistance to growth factor activation of intracellular signaling. ErbB2 degradation was also induced by the physiological stress of ␤-adrenergic receptor stimulation in electrically stimulated cells. These results support a role for Hsp90 as an ATP sensor that modulates tissue growth factor responsiveness under metabolically stressed conditions and provide a novel mechanism by which cellular responsiveness to growth factor stimulation is modulated by cellular energy charge.The physiological mechanisms by which cells dynamically shift between steady states of tissue function, for example from tissue growth to cell survival during periods of metabolic stress, are incompletely understood. The activity of large sets of proteins must be coordinately regulated during these shifts. Many of the proteins involved in cell growth are stabilized by the constitutively expressed chaperone heat shock protein (Hsp) 1 90 (1, 2). Dissociation of Hsp90 from its client proteins induced by Hsp90 inhibitors leads to rapid degradation of proteins involved in cell growth and the activation of a stress response (3). Thus, pharmacologically induced disruption in Hsp90 chaperone function alone can cause a cell to "shift gears" to a stress-mode.Hsp90 inhibitors such as geldanamycin (GA) bind with high affinity to a conserved pocket in the Hsp90 family of proteins and thereby prevent the ATP binding that is required for chaperone function (4). The relative affinity of Hsp90 for GA, ADP, and ATP were recently measured and exhibited dissociation constants of 0.2, 12, and 124 M, respectively (5). The relatively high affinity of Hsp90 for GA is consistent with its established potency as an inhibitor of Hsp90 chaperone function. The ϳ10-fold higher affinity of Hsp90 for ADP versus ATP is intriguing. Under basal conditions, when the intracellular [ATP]/[ADP]ratio is between 2 and 10:1 (6), the higher affinity of Hsp90 for ADP suggests that a small drop in the ATP/ADP ratio will result in a relatively large drop in the proportion of Hsp90 occupied by ATP and, therefore, available for client protein stabilization.These observations led us to hypothesize that Hsp90 ...

Transactivation of the epidermal growth factor receptor in responses to myocardial stress and cardioprotection

“…Myocyte ErbB2 levels have been shown to decline with metabolic stress (glycolytic or mitochondrial inhibition) associated with ATP depletion (Peng et al, 2005) and hypoxia (Viswanath et al, 2011). Such findings support negative impacts of ischaemic/hypoxic stress on ErbB2 expression and thereby EGFR functionality.…”

“…Proteosomal degradation of the dimer partner ErbB2 is limited by the ATP-sensitive chaperone function of Hsp90 (Xu et al, 2001), thus reductions in cellular ATP result in ErbB2 dissociation and degradation (Peng et al, 2005).…”

The neuroblastoma tumour-suppressor TrkAI and its oncogenic alternative TrkAIII splice variant exhibit geldanamycin-sensitive interactions with Hsp90 in human neuroblastoma cells

“…However, because of lack of adequate mono-specific anti-Hsp90a and Hsp90b antibodies for FACS and IF, we are unable to state whether Hsp90a, in addition to Hsp90b, is also expressed at the SH-SY5Y cell surface. Cell surface Hsp90 (a/b) expression was also detected in pcDNA and TrkAIII transfectants, adding SH-SY5Y cells to other tumour and normal cell types that express cell surface Hsp90 (a/b) (Becker et al, 2004;Sidera et al, 2004Sidera et al, , 2008 and TrkAI to other cell surface receptors that depend on interaction with Hsp90 for stability (Vega and De Maio, 2003;Peng et al, 2005).…”

MS-275, a novel histone deacetylase inhibitor with selectivity against HDAC1, induces degradation of FLT3 via inhibition of chaperone function of heat shock protein 90 in AML cells

“…3A). Acetylation of HSP90 is linked to the inactivation of its chaperone activity, leading to ubiquitination of the client proteins [14,15]. We next explored whether MS-275 induced ubiquitination of FLT3 in leukemia cells.…”

“…Recent studies showed that inhibition of HSP90 by 17-allylamino-demethoxy geldanamycin (17-AAG) provoked degradation of FLT3-ITD via ubiquitin/proteasome pathway and inhibited the proliferation of leukemia cells with FLT3-ITD [15,16].…”