RAIDD is required for apoptosis of PC12 cells and sympathetic neurons induced by trophic factor withdrawal.

Caspase 2 has been implicated in trophic deprivation-induced neuronal death. We have shown that overexpression of the caspase 2-binding protein RAIDD induces neuronal apoptosis, acting synergistically with trophic deprivation. Currently, we examine the role of endogenous RAIDD in apoptosis of PC12 cells and sympathetic neurons. Expression of a truncated caspase recruitment domain-only form of caspase 2, which presumably disrupts the RAIDD interaction with endogenous caspase 2, attenuated trophic deprivation-induced apoptosis. Furthermore, downregulation of RAIDD by small interfering RNA led to inhibition of trophic deprivation-induced death, whereas death induced by DNA damage, which is not caspase 2-mediated, was not inhibited. Therefore, RAIDD, likely through interaction with caspase 2, is involved in trophic deprivation-induced neuronal apoptosis. This is the first demonstration of the involvement of RAIDD in apoptosis, and provides further support for the idea that apoptotic pathways in the same system may differ depending on the initiating stimulus.

RAIDD aggregation facilitates apoptotic death of PC12 cells and sympathetic neurons.

In human cell lines, the caspase 2 adaptor RAIDD interacts selectively with caspase 2 through its caspase recruitment domain (CARD) and leads to caspase 2-dependent death. Whether RAIDD induces such effects in neuronal cells is unknown. We have previously shown that caspase 2 is essential for apoptosis of trophic factor-deprived PC12 cells and rat sympathetic neurons. We report here that rat RAIDD, cloned from PC12 cells, interacts with rat caspase 2 CARD. RAIDD overexpression induced caspase 2 CARD- and caspase 9-dependent apoptosis of PC12 cells and sympathetic neurons. Apoptosis correlated with the formation of discrete perinuclear aggregates. Both death and aggregates required the expression of full-length RAIDD. Such aggregates may enable more effective activation of caspase 2 through close proximity. Following trophic deprivation, RAIDD overexpression increased death and aggregate formation. Therefore, RAIDD aggregation is important for its death-promoting effects and may play a role in trophic factor withdrawal-induced neuronal apoptosis.

Inhibitors of trypsin-like serine proteases prevent DNA damage-induced neuronal death by acting upstream of the mitochondrial checkpoint and of p53 induction.

We have previously shown that the pharmacological agents 4-(2-aminoethyl)=benzenesulfonylfluoride hydrochloride (AEBSF) and Na-p-tosyl-L-lysine chloromethylketone (TLCK), inhibitors of trypsin-like serine proteases, prevent the death of trophic factor-deprived PC12 cells and sympathetic neurons. Both AEBSF and TLCK inhibit caspase activation in this model, but it is unclear whether they do so indirectly or through a direct effect at the level of the caspases. In the current study, we have used these agents in another model of neuronal death that is induced by DNA damage. We find that both agents delay the death of DNA-damaged PC12 cells, neonatal rat sympathetic neurons and embryonic rat cortical neurons. As in the trophic deprivation model, they act upstream of the caspases. In addition, they prevent mitochondrial alterations, such as cytochrome c release or loss of transmembrane potential. In contrast, the general caspase inhibitor bok-asp-fmk does not prevent cytochrome c release and has only a partial and transient effect on loss of transmembrane potential. Interestingly, both AEBSF and TLCK prevent the induction and nuclear accumulation of p53 that is induced by DNA damage in cortical neurons. Therefore, these serine protease inhibitors act at a point upstream in the apoptotic pathway, prior to p53 induction and the mitochondrial checkpoint, to delay neuronal death in this model, and do not act at the level of the caspases. We conclude that therapeutic strategies based on serine protease inhibition may be useful in preventing neuronal cell death.

Use of a short fragment of the C-terminal E gene for detection and characterization of two new lineages of dengue virus 1 in India.

Here we propose the use of a 216-nucleotide fragment located in the carboxyl terminus of the E gene (E-COOH) and a pairwise-based comparison method for genotyping of dengue virus 1 (DENV-1) strains. We have applied this method to the detection and characterization of DENV-1 in serum samples from travelers returning from the tropics. The results obtained with the typing system correlate with the results obtained by comparison of the sequences of the entire E gene of the strains. The approach demonstrates utility in plotting the distribution and circulation of different genotypes of DENV-1 and also suggests the presence of two new clades of Indian strains. The integration of the method with an online database and a typing characterization tool enhances its strength. Additionally, the analysis of the complete E gene of DENV-1 strains suggested the occurrence of a nondescribed recombination event in the China GD23-95 strain. We propose the use of this methodology as a tool for real-time epidemiological surveillance of dengue virus infections and their pathogenesis.

Apoptosis and the conformational change of Bax induced by proteasomal inhibition of PC12 cells are inhibited by bcl-xL and bcl-2.

The function of the proteasome has been linked to various pathologies, including cancer and neurodegeneration. Proteasomal inhibition can lead to death in a variety of cell types, however the manner in which this occurs is unclear, and may depend on the particular cell type. In this work we have extended previous findings pertaining to the effects of pharmacological proteasomal inhibitors on PC12 cells, by examining in more detail the induced death pathway. We find that cell death is apoptotic by ultrastructural criteria. Caspase 9 and 3 are processed, cytochrome c is released from the mitochondria and a dominant negative form of caspase 9 prevents death. Furthermore, Bax undergoes a conformational change and is translocated to the mitochondria in a caspase-independent fashion. Total cell levels of Bax however do not change, whereas levels of the BH3-only protein Bim increase with proteasomal inhibition. Transient overexpression of bcl-xL or, to a lesser extent, of bcl-2, significantly decreased apoptotic death and prevented Bax conformational change. We conclude that death elicited by proteasomal inhibition of PC12 cells follows a classical "intrinsic" pathway. Significantly, antiapoptotic bcl-2 family members prevent apoptosis by inhibiting Bax conformational change. Increased levels of Bim may contribute to cell death in this model.

Molecular identification of adenoviruses in clinical samples by analyzing a partial hexon genomic region.

Here we present a system for adenovirus detection and genotyping based on PCR amplification and phylogenetic analysis of a conserved hexon gene fragment. The system was validated using 157 sequences (86 previously typed and 71 clinical samples) and correctly identified species and serotype in 100% and 84% of sequences, respectively. Known associations between specific serotypes and clinical syndromes are verified. Possible new associations are described to allow further independent testing.

Molecular identification of mumps virus genotypes from clinical samples: standardized method of analysis.

A sensitive nested reverse transcription-PCR assay, targeting a short fragment of the gene encoding the small hydrophobic protein (SH gene), was developed to allow rapid characterization of mumps virus in clinical samples. The sensitivity and specificity of the assay were established using representative genotypes A, B, C, D, E, and F. Mumps virus RNA was characterized directly from cerebrospinal fluid (CSF) samples and in extracts of mumps virus isolates from patients with various clinical syndromes. Direct sequencing of products and subsequent phylogenetic analysis enabled genetic classification. A simple web-based system of sequence analysis was established. The study also allowed characterization of mumps virus strains from Argentina as part of a new subgenotype. This PCR assay for characterization of mumps infections coupled to a web-based analytical program provides a rapid method for identification of known and novel strains.

A new tool for the diagnosis and molecular surveillance of dengue infections in clinical samples.

Dengue fever and dengue haemorrhagic fever are amongst the most important challenges in tropical diseases due to their expanding geographical distribution, increasing outbreak frequency, hyperendemicity and evolution of virulence. Here, the use of a RT-nested PCR for both the diagnosis and genetic characterization of dengue infections in clinical samples is described.