Role of Cytoskeleton Proteins in the Morphological Changes During Apoptotic Cell Death of Cerebellar Granule Neurons

Effect of staurosporine in the morphology and viability of cerebellar astrocytes: role of reactive oxygen species and NADPH oxidase

Cell death implies morphological changes that may contribute to the progression of this process. In astrocytes, the mechanisms involving the cytoskeletal changes during cell death are not well explored. Although NADPH oxidase (NOX) has been described as being a critical factor in the production of ROS, not much information is available about the participation of NOX-derived ROS in the cell death of astrocytes and their role in the alterations of the cytoskeleton during the death of astrocytes. In this study, we have evaluated the participation of ROS in the death of cultured cerebellar astrocytes using staurosporine (St) as death inductor. We found that astrocytes express NOX1, NOX2, and NOX4. Also, St induced an early ROS production and NOX activation that participate in the death of astrocytes. These findings suggest that ROS produced by St is generated through NOX1 and NOX4. Finally, we showed that the reorganization of tubulin and actin induced by St is ROS independent and that St did not change the level of expression of these cytoskeletal proteins. We conclude that ROS produced by a NOX is required for cell death in astrocytes, but not for the morphological alterations induced by St.

Involvement of the proteasome and caspase activation in hippocampal long-term depression induced by the serine protease subtilisin

The serine protease subtilisin-A produces a long-term depression (LTD) of synaptic potentials in hippocampal slices which differs mechanistically from classical LTD. Since caspases have been implicated in hippocampal plasticity, this study examined a possible role for these enzymes in subtilisin-induced LTD. Subtilisin produced a concentration-dependent decrease in the size of field excitatory synaptic potentials (fEPSPs), which was not prevented or modified by the caspase inhibitors Z-VAD(OMe)-fmk and Z-DEVD-fmk. Similarly Z-VAD(OMe)-fmk did not modify the selective loss of protein expression produced by subtilisin. Subtilisin reduced the expression of procaspase-3 and caspase-9 but, while caspase-9 was converted to its conventionally activated form (39 kDa), caspase-3 was metabolised along a non-canonical pathway to a 29/30 kDa protein rather than the classical 17/19 kDa fragments. Both Z-VAD(OMe)-fmk and Z-DEVD-fmk were unable to prevent the reduced expression of Postsynaptic Density Protein-95, Vesicle-Associated Membrane Protein-1 and Unco-ordinated 5H3 proteins produced by subtilisin, although MG132 did produce partial recovery from subtilisin-induced depression of fEPSPs. When tested on long-term potentiation (LTP) induced by theta stimulation in the stratum radiatum, MG132 inhibited the immediate increase in fEPSP size but generated a higher plateau LTP. Twin LTP stimulation generated a further increase in LTP amplitude in control slices but not in slices exposed to MG132. The results indicate that subtilisin does produce caspase activation but that this does not contribute to its induction of LTD. However, activation of the proteasome does contribute to subtilisin-induced LTD and may also play a modulatory role in electrically induced LTP.