Mohammad Hassan Shehata

Many studies have reported the roles played by regulated proteolysis in synaptic plasticity and memory, but the role of autophagy in neurons remains unclear. In mammalian cells, autophagy functions in the clearance of long-lived proteins and organelles and in adaptation to starvation. In neurons, although autophagy-related proteins (ATGs) are highly expressed, autophagic activity markers, autophagosome (AP) number, and light chain protein 3-II (LC3-II) are low compared with other cell types. In contrast, conditional knock-out of ATG5 or ATG7 in mouse brain causes neurodegeneration and behavioral deficits. Therefore, this study aimed to test whether autophagy is especially regulated in neurons to adapt to brain functions. In cultured rat hippocampal neurons, we found that KCl depolarization transiently increased LC3-II and AP number, which was partially inhibited with APV, an NMDA receptor (NMDAR) inhibitor. Brief low-dose NMDA, a model of chemical long-term depression (chem-LTD), increased LC3-II with a time course coincident with Akt and mammalian target of rapamycin (mTOR) dephosphorylation and degradation of GluR1, an AMPA receptor (AMPAR) subunit. Downstream of NMDAR, the protein phosphatase 1 inhibitor okadaic acid, PTEN inhibitor bpV(HOpic), autophagy inhibitor wortmannin, and short hairpin RNA-mediated knockdown of ATG7 blocked chem-LTD-induced autophagy and partially recovered GluR1 levels. After chem-LTD, GFP-LC3 puncta increased in spines and in dendrites when AP-lysosome fusion was blocked. These results indicate that neuronal stimulation induces NMDAR-dependent autophagy through PI3K-Akt-mTOR pathway inhibition, which may function in AMPAR degradation, thus suggesting autophagy as a contributor to NMDAR-dependent synaptic plasticity and brain functions.

Regions required for chicken glycine decarboxylase gene transcription were examined. A region between -82 and +22 (-82/+22) with motifs similar to binding sites for Sp1, NF-Y and CP2 was assigned to the proximal promoter active in both chicken hepatoma cell line, LMH, and hepatocytes in primary culture. In LMH cells, a genomic region, KX, between KpnI (-4155) and XbaI (-2113) sites changed promoter activity with the aid of four additional genomic regions termed upstream regulator regions for suppression (UpRS) and activation (UpRA) of transcription. Those precise segments are UpR1S (-376/-346), UpR1A (-345/-291), UpR2S (-137/-108) and UpR2A (-107/-83). Within KX, -4155/-3605 activates and -3604/-3367 suppresses the promoter. -3366/-3024 activates or suppresses the promoter, probably with different UpR counterparts. -2197/-2113 restores the actions of -3366/-3024. While in LMH cells, the upstream UpRs abrogate the functions of immediately downstream UpRs, UpR1S or UpR2S or both may be at least less active in hepatocytes than in LMH cells. Nuclear extracts from various chicken tissues and LMH cells had UpR2A binding proteins in different populations, suggesting that together with the UpRs, the segments in KX are involved in the regulation of cell type-specific transcription of this gene.

Sanazole has been tested clinically as a hypoxic cell radiosensitizer. The aim of the present study was to investigate whether sanazole enhances apoptosis induced by hyperthermia at 44 degrees C for 20 min in human lymphoma U937 cells. Sanazole alone induced continuous increase in the intracellular superoxide generation in a time-dependent manner and transient increase in the peroxide formation, which further were enhanced at 1 hour after HT treatment. Moreover, when the cells were treated first with 10 mM sanazole for 40 min, exposed to HT at 44 degrees C for 20 min and the cells were further treated with the drug at 37 degrees C for 6 h, a significant enhancement of HT-induced apoptosis was evidenced by DNA fragmentation, morphological changes and phosphatidylserine externalization. Studying the apoptotic pathways involved in this enhancement, we found that loss of the mitochondrial membrane potential, release of cytochrome c from mitochondria to cytosol, and activation of caspase-3 and caspase-8 was enhanced significantly in the U937 cells after the combined treatment. Moreover, this combination enhanced activation of Bid, and down regulation of Hsp70. In addition, an increase in the intracellular Ca(2+) concentration ([Ca(2+)](i)), and externalization of Fas were observed immediately after sanazole and HT treatment. Our data indicate that sanazole can enhance the hyperthermia induced-apoptosis through the Fas-caspase-8- and [Ca(2+)](i)-dependent apoptotic pathways. In addition, the down regulation of Hsp70 contributed to this enhancement.

Mutations in human neuroserpin gene cause an autosomal dementia, familial encephalopathy with neuroserpin inclusion bodies (FENIB). We generated and analyzed transgenic mice expressing high levels of either FENIB-type (G392E) or wild-type human neuroserpin in neurons of the central nervous system. G392E neuroserpin accumulated age-dependently in neurons of the neocortex, thalamus, amygdala, pons, and spinal cord of homozygous transgenic mice. Such accumulations were not observed in hemizygous transgenic mice nor in transgenic mice for wild-type neuroserpin. In differential centrifugation of brain homogenates, G392E neuroserpin recovered in the nucleus-rich fraction dramatically increased along with aging, suggesting that the aggregations gradually increase their densities presumably by their conversion into heavier and more compact configurations. In immunoelectron microscopical analyses, immunopositivities for G392E neuroserpin were found not only in endoplasmic reticulum but also in lysosomes. G392E neuroserpin transgenic mice were much more susceptible to seizures induced by kainate administration than nontransgenic mice. Overall, G392E neuroserpin accumulated in the central nervous system neurons of transgenic mice in mutation-, aging-, and gene dosage-dependent manners. The established transgenic mice will be valuable to elucidate not only mechanisms for the formation of G392E neuroserpin aggregations but also pathways for the degradation and/or clearance of the already formed aggregations in neurons.