Weixing Li

Structure of glutamate carboxypeptidase II, a drug target in neuronal damage and prostate cancer

Membrane‐bound glutamate carboxypeptidase II (GCPII) is a zinc metalloenzyme that catalyzes the hydrolysis of the neurotransmitter N‐acetyl‐L‐aspartyl‐L‐glutamate (NAAG) to N‐acetyl‐L‐aspartate and L‐glutamate (which is itself a neurotransmitter). Potent and selective GCPII inhibitors have been shown to decrease brain glutamate and provide neuroprotection in preclinical models of stroke, amyotrophic lateral sclerosis, and neuropathic pain. Here, we report crystal structures of the extracellular part of GCPII in complex with both potent and weak inhibitors and with glutamate, the product of the enzymes hydrolysis reaction, at 2.0, 2.4, and 2.2 Å resolution, respectively. GCPII folds into three domains: protease‐like, apical, and C‐terminal. All three participate in substrate binding, with two of them directly involved in C‐terminal glutamate recognition. One of the carbohydrate moieties of the enzyme is essential for homodimer formation of GCPII. The three‐dimensional structures presented here reveal an induced‐fit substrate‐binding mode of this key enzyme and provide essential information for the design of GCPII inhibitors useful in the treatment of neuronal diseases and prostate cancer.

Post-treatment with a novel PARG inhibitor reduces infarct in cerebral ischemia in the rat

Poly(ADP-ribose) is synthesized from nicotinamide adenine dinucleotide (NAD(+)) by poly(ADP-ribose) polymerase (PARP) and degraded by poly(ADP-ribose) glycohydrolase (PARG). Overactivation of the poly(ADP-ribose) pathway increases nicotinamide and decreases cellular NAD(+)/ATP, which leads to cell death. Blocking poly(ADP-ribose) metabolism by inactivating PARP has been shown to reduce ischemia injury. We investigated whether disrupting the poly(ADP-ribose) cycle by PARG inhibition could achieve similar protection. We demonstrate that either pre- or post-ischemia treatment with 40 mg/kg of N-bis-(3-phenyl-propyl)9-oxo-fluorene-2,7-diamide, a novel PARG inhibitor, significantly reduces brain infarct volumes by 40-53% in a rat model of focal cerebral ischemia. Our result provides the first evidence that PARG inhibitors can ameliorate ischemic brain damage in vivo, in support of PARG as a new therapeutic target for treating ischemia injury.

PARG activity mediates intestinal injury induced by splanchnic artery occlusion and reperfusion

Poly (ADP‐ribosyl)ation, an early post‐translational modification in response to DNA damage, is catalyzed by poly (ADP‐ribose) polymerase (PARP‐1) and catabolized by poly(ADP‐ribose) glycohydrolase (PARG). The aim of this study was to investigate the role of PARG on the modulation of the inflammatory response caused by splanchnic ischemia and reperfusion. SAO shock in rats and wild‐type (WT) mice was associated with a significant neutrophil infiltration in the ileum and production of tumor necrosis factor‐α (TNF‐α). Reperfused ileum tissue sections from SAO‐shocked WT mice and rats showed positive staining for P‐selectin and ICAM‐1 localized mainly in the vascular endothelial cells. Genetic disruption of the PARG gene in mice or pharmacological inhibition of PARG by PARG inhibitors significantly improved the histological status of the reperfused tissues associated with reduced expression of P‐selectin and ICAM‐1, neutrophil infiltration into the reperfused intestine, and TNF‐α production. These results suggest that PARG activity modulates the inflammatory response in ischemia/ reperfusion and participates in end (target) organ damage under these conditions.—Cuzzocrea, S., Di Paola, R., Mazzon, E., Cortes U., Genovese, T., Muià, C., Li, W., Xu, W., Li, J.‐H., Zhang, J., Wang, Z.‐Q. PARG activity mediates intestinal injury induced by splanchnic artery occlusion and reperfusion. FASEB J. 19, 558–566 (2005)

Synthesis of substituted 5[H]phenanthridin-6-ones as potent poly(ADP-ribose)polymerase-1 (PARP1) inhibitors

1-, 2-, 3-, 4-, 8-, or 10-Substituted 5(H)phenanthridin-6-ones were synthesized and found to be potent PARP1 inhibitors. Among the 28 compounds prepared, some showed not only low IC(50) values (compound 1b, 10 nM) but also desirable water solubility characteristics. These properties, which are superior to the common PARP1 inhibitors such as benzamides and isoquinolin-1-ones, are essential for potential therapeutic usage. The variety of compounds allows SAR analysis of favored substituents and substituted positions on 5(H)phenanthridin-6-one ring.