Phosphono Analogues of 2‐Oxoglutarate Protect Cerebellar Granule Neurons upon Glutamate Excitotoxicity

Abstract

Glutamate excitotoxicity is an important contributor to neuronal loss. Glutamate-induced Ca(2+) deregulation and accompanying mitochondrial depolarization are closely associated with the onset of apoptotic and necrotic neuronal death. We investigated the role in these phenomena of 2-oxoglutarate dehydrogenase (OGDH), the enzyme participating in mitochondrial degradation of glutamate. To achieve this goal, we used specific effectors of cellular OGDH, succinyl phosphonate and its phosphonoethyl ether. Preincubation of cerebellar granule neurons with these phosphono analogues of 2-oxoglutarate was shown to protect the cells from glutamate-induced Ca(2+) deregulation and irreversible mitochondrial depolarization, followed simultaneously by fluorescence of fura-2FF and rhodamine 123, respectively. The protection was characterized by delay in onset and decreased propagation of Ca(2+) deregulation and by reversibility of the associated mitochondrial depolarization. Compared to its phosphonoethyl ether, succinyl phosphonate exhibited both higher affinity to OGDH in vitro and better protection from Ca(2+) deregulation in situ, supporting the assumption that neuroprotection by phosphonates involves their interaction with cellular OGDH. Preincubation of cerebellar granule neurons with succinyl phosphonate decreased neuronal death after excitotoxic action of glutamate. Thus, specific inhibitors of OGDH alleviate glutamate-induced calcium deregulation, mitochondrial depolarization, and neuronal death.

Yeast two-hybrid screening of proteins interacting with plasmin receptor subunit: C-terminal fragment of annexin A2

“…The activity of the enzyme is much lower in Alzheimer's disease, and there are reports of the enzyme's susceptibility to modification by oxidative stress [29] . Inhibition of OGDH activity alleviates glutamate-induced calcium deregulation, mitochondrial depolarization, and neuronal death [30] . PAPD4 (GLD2) is an important regulator of late spermatogenesis and is the first example of a GLD-2 family member playing a significant role in male gametogenesis [31] .…”

Behavioral Impact of the Regulation of the Brain 2-Oxoglutarate Dehydrogenase Complex by Synthetic Phosphonate Analog of 2-Oxoglutarate: Implications into the Role of the Complex in Neurodegenerative Diseases

“…In cellular experiments, SP was shown to protect from the glutamate-induced ROS [18] and excitotoxicity [16, 17, 21]. Owing to this, we tested if SP would show a protective action on the behavioral and biochemical changes induced by hypoxia.…”

“…First of all, the inhibition by SP may induce compensatory effects up-regulating OGDHC (Figure 3). Furthermore, as shown earlier, SP binding to the active site protects the essential groups of enzyme from irreversible modifications causing inactivation [16, 17]. The SP binding also prevents the enzyme from catalysis of the side reactions, including production of ROS and enzyme-bound radicals irreversibly damaging OGDHC [18].…”

“…In particular, increased synthesis of the first component of OGDHC, E1o, was observed in response to the acute ethanol-induced stress [33]. Besides, in addition to its action as the reversible OGDHC inhibitor [15], SP is a protector of OGDHC from an irreversible inactivation occurring in the course of catalysis [16, 17]. During a certain time period, this protective effect may manifest itself as an apparent increase in the OGDHC activity compared to the control value with the unprotected enzyme (Figure 3).…”

“…To reveal molecular mechanisms of the association between neuropathologies and OGDHC function, we introduced specific inhibitors of OGDHC [15], which have been successfully applied in recent years for cellular [16–19], tissue [20], and animal [21] studies. Having the phosphonate residue instead of the leaving carboxyl group of 2-oxoglutarate, these synthetic inhibitors target the starting and rate-limiting E1o component of OGDHC in a highly specific manner, imitating transition state of the E1o-catalyzed step [15, 22].…”