Here we show that

long-lasting membrane depolarization induced by elevated extracellular K+ recruits nitric oxide (NO)/soluble guanylyl cyclase/protein kinase G signaling pathway, induces 8-nitroguanosine 3′,5′-cyclic monophosphate (8-nitro-cGMP)-mediated protein S-guanylation, and confers dopaminergic neuroprotection. Treatment of primary mesencephalic cell cultures with 1-methyl-4-phenylpyridinium (MPP+) for 72 h decreased the number of dopaminergic neurons, whereas the cell loss was markedly inhibited by elevated extracellular concentration Geneticin clinical trial of K+ (+ 40 mM). The neuroprotective effect of elevated extracellular K+ was significantly attenuated by tetrodotoxin (a Na+ channel blocker), amlodipine (a voltage-dependent Ca2+ channel blocker), N-omega-nitro-L-arginine methyl ester (L-NAME) (a nitric oxide synthase inhibitor), 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) (a soluble guanylyl cyclase inhibitor), and KT5823 or Rp-8-bromo-beta-phenyl-1,N-2-ethenoguanosine 3′,5′-cyclic monophosphorothioate (Rp-8-Br-PET-cGMPS) (protein kinase G inhibitors). Elevated extracellular K+ increased 8-nitro-cGMP production resulting in the induction of protein S-guanylation in cells in mesencephalic

cultures including dopaminergic neurons. In addition, exogenous application of 8-nitro-cGMP protected dopaminergic neurons from MPP+ cytotoxicity, VE-822 in vitro which was prevented by zinc protoporphyrin IX, an inhibitor of heme oxygenase-1 (HO-1). Zinc protoporphyrin IX also inhibited the neuroprotective effect of elevated extracellular K+. On the other hand, KT5823 or Rp-8-Br-PET-cGMPS did not inhibit the induction of HO-1 protein expression by 8-nitro-cGMP, although these protein kinase G inhibitors abrogated the neuroprotective effect of 8-nitro-cGMP. These results suggest that protein Pregnenolone S-guanylation (leading to HO-1 induction) as well as canonical protein kinase G

signaling pathway plays an important role in NO-mediated, activity-dependent dopaminergic neuroprotection. (c) 2012 IBRO. Published by Elsevier Ltd. All rights reserved.”
“Protein degradation is a fundamental biological process, which is essential for the maintenance and regulation of normal cellular function. In humans and animals, proteins can be degraded by a number of mechanisms: the ubiquitin-proteasome system, autophagy and intracellular proteases. The advances in contemporary protein analysis means that proteomics is increasingly being used to explore these key pathways and as a means of monitoring protein degradation. The dysfunction of protein degradative pathways has been associated with the development of a number of important diseases including cancer, muscle wasting disorders and neurodegenerative diseases. This review will focus on the role of proteomics to study cellular degradative processes and how these strategies are being applied to understand the molecular basis of diseases arising from disturbances in protein degradation.