Prostaglandin J2 alters gene expression patterns and 26S proteasome assembly in human neuroblastoma cells

Many neurodegenerative disorders are characterized by two pathological hallmarks: progressive loss of neurons and occurrence of inclusion bodies containing ubiquitinated proteins. The mechanisms responsible for these pathological features remain elusive. Inflammation may be critical to neurodegeneration associated with ubiquitin-protein aggregates. We previously showed that prostaglandin J2 (PGJ2), one of the endogenous products of inflammation, induces neuronal death and accumulation of ubiquitinated proteins into distinct aggregates. We now report that temporal microarray analysis of human neuroblastoma SK-N-SH cells treated with PGJ2 revealed changes relevant to neurodegeneration. PGJ2 triggered a “repair” response including increased expression of heat shock, protein folding, stress and cellular defense genes. PGJ2 also decreased expression of DNA repair genes and increased expression of apoptotic genes. Overtime pro-death responses prevailed over pro-survival responses, leading to cellular demise. Furthermore, PGJ2 increased the expression of proteasome and other ubiquitin-proteasome pathway genes. This increase failed to overcome PGJ2-inhibition of 26S proteasome activity. Ubiquitinated proteins are degraded by the 26S proteasome, shown here to be the most active proteasomal form in SK-N-SH cells. We demonstrate that PGJ2 impairs 26S proteasome assembly, which is an ATP-dependent process. Interestingly, PGJ2 is known to perturb mitochondrial function, which could be critical to the observed 26S proteasome disassembly and suggest a crosstalk between mitochondrial and proteasomal impairment. In conclusion neurotoxic products of inflammation, such as PGJ2, may play a role in neurodegenerative disorders associated with the aggregation of ubiquitinated proteins by impairing 26S proteasome activity and inducing a chain of events that culminates in neuronal cell death. Keywords: Drug response time course SK-N-SH cells were treated with 20uM PGJ2 for 4, 8, 16 and 24h. Each time point was repeated two times. For each time point, total RNA from untreated control and PGJ2-treated cells was isolated, labeled and co-hybridized onto Human 19K oligonucleotide arrays.