Human adenovirus type 5 induces cell lysis through autophagy and autophagy-triggered caspase activity.

Oncolytic adenoviruses, such as Delta-24-RGD, are promising therapies for patients with brain tumor. Clinical trials have shown that the potency of these cancer-selective adenoviruses should be increased to optimize therapeutic efficacy. One potential strategy is to increase the efficiency of adenovirus-induced cell lysis, a mechanism that has not been clearly described. In this study, for the first time, we report that autophagy plays a role in adenovirus-induced cell lysis. At the late stage after adenovirus infection, numerous autophagic vacuoles accompany the disruption of cellular structure, leading to cell lysis. The virus induces a complete autophagic process from autophagosome initiation to its turnover through fusion with the lysosome although the formation of the autophagosome is sufficient for virally induced cell lysis. Importantly, downmodulation of autophagy genes (ATG5 or ATG10) rescues the infected cells from being lysed by the virus. Moreover, autophagy triggers caspase activity via the extrinsic FADD/caspase 8 pathway, which also contributes to adenovirus-mediated cell lysis. Therefore, our study implicates autophagy and caspase activation as part of the mechanism for cell lysis induced by adenovirus and suggests that manipulation of the process is a potential strategy to optimize clinical efficacy of oncolytic adenoviruses.

Addressing the Language Binding Problem With Dynamic Functional Connectivity During Meaningful Spoken Language Comprehension.

During speech, how does the brain integrate information processed on different timescales and in separate brain areas so we can understand what is said? This is the language binding problem. Dynamic functional connectivity (brief periods of synchronization in the phase of EEG oscillations) may provide some answers. Here we investigate time and frequency characteristics of oscillatory power and phase synchrony (dynamic functional connectivity) during speech comprehension. Twenty adults listened to meaningful English sentences and non-sensical "Jabberwocky" sentences in which pseudo-words replaced all content words, while EEG was recorded. Results showed greater oscillatory power and global connectivity strength (mean phase lag index) in the gamma frequency range (30-80 Hz) for English compared to Jabberwocky. Increased power and connectivity relative to baseline was also seen in the theta frequency range (4-7 Hz), but was similar for English and Jabberwocky. High-frequency gamma oscillations may reflect a mechanism by which the brain transfers and integrates linguistic information so we can extract meaning and understand what is said. Slower frequency theta oscillations may support domain-general processing of the rhythmic features of speech. Our findings suggest that constructing a meaningful representation of speech involves dynamic interactions among distributed brain regions that communicate through frequency-specific functional networks.

Learning, neural plasticity and sensitive periods: implications for language acquisition, music training and transfer across the lifespan.

Sensitive periods in human development have often been proposed to explain age-related differences in the attainment of a number of skills, such as a second language (L2) and musical expertise. It is difficult to reconcile the negative consequence this traditional view entails for learning after a sensitive period with our current understanding of the brain's ability for experience-dependent plasticity across the lifespan. What is needed is a better understanding of the mechanisms underlying auditory learning and plasticity at different points in development. Drawing on research in language development and music training, this review examines not only what we learn and when we learn it, but also how learning occurs at different ages. First, we discuss differences in the mechanism of learning and plasticity during and after a sensitive period by examining how language exposure versus training forms language-specific phonetic representations in infants and adult L2 learners, respectively. Second, we examine the impact of musical training that begins at different ages on behavioral and neural indices of auditory and motor processing as well as sensorimotor integration. Third, we examine the extent to which childhood training in one auditory domain can enhance processing in another domain via the transfer of learning between shared neuro-cognitive systems. Specifically, we review evidence for a potential bi-directional transfer of skills between music and language by examining how speaking a tonal language may enhance music processing and, conversely, how early music training can enhance language processing. We conclude with a discussion of the role of attention in auditory learning for learning during and after sensitive periods and outline avenues of future research.

Autophagy regulation in cancer development and therapy.

Autophagy is a cellular process to degrade long-lived or malfunctioning proteins and obsolete or damaged organelles. It maintains cellular homeostasis and helps cells survive stressful conditions. Tumor suppressors mostly positively regulate autophagy, whereas oncogene products usually inhibit autophagy. Alterations in key autophagy genes have also been shown to affect cancer development. However, the role of autophagy in cancer depends on the status of the cells and can either suppress or promote tumor growth. In the present review, we report on the current state of knowledge about the reciprocal regulation of autophagy and the potential role of autophagy played in cancer development and therapy.

The E1B19K oncoprotein complexes with Beclin 1 to regulate autophagy in adenovirus-infected cells.

The mechanisms underlying adenovirus-mediated autophagy are currently unknown. Recently, members of the Bcl-2 protein family have been associated with autophagy. It was also reported that the Bcl-2 homology-3 (BH3) domain encompassed by both Beclin 1 and Bcl-2-like proteins is essential for their pro-autophagy or anti-autophagy functions. Here, we report for the first time that E1B19K, the adenovirus BH3 domain protein, interacts with Beclin 1 to initiate autophagy. Using immunoprecipitation assays we showed that expression of E1B19K in the host cell disrupted the physical interactions between Beclin 1 and Bcl-2 proteins. The displacement of Bcl-2 was coincident with the recruitment of PI3KC3 to the Beclin 1/E1B19K complexes. As a result of the changes in the components of the Beclin 1 interactome, there was activation of PI3KC3, as showed by the identification of PI3K-mediated lipid phosphorylation, and subsequent formation of autophagosomes. Importantly, the BH3 functional domain of E1B19K protein was required for the heterodimerization with Beclin 1. We also showed that transfer of E1B19K was sufficient to trigger autophagy in cancer cells. Consistent with these data, mutant adenoviruses encompassing a deletion of the E1B19K gene produced a marked deficiency in the capability of the virus to induce autophagy as showed by examining the lipidation and cleavage of LC3-I as well as the subcellular localization of LC3-II, the decrease in the levels of p62, and the formation of autophagosomes. Our work offers new information on the mechanisms of action of the adenoviral E1B19K protein as partner of Beclin 1 and positive regulator of autophagy.

Autophagy pathways in glioblastoma.

Glioma cells are more likely to respond to therapy through autophagy than through apoptosis. The most efficacious cytotoxic drugs employed in glioma therapy, such as temozolomide and rapamycin, induce autophagy. Oncolytic adenoviruses, which will soon be tested in patients with gliomas at the University of Texas M. D. Anderson Cancer Center, also induce autophagy. Autophagy in gliomas thus represents a promising mechanism that may lead to new glioma therapies. In this chapter, we present the methods for studying autophagy in glioma cells, including assessment of in vitro cellular markers acidic vesicle organelles, and green fluorescent protein (GFP)-LC3 punctation; biochemical markers LC3-I/II conversion, p62 degradation, Atg12-Atg5 accumulation, and p70S6K dephosphorylation; and ultrastucture of the autophagosomes. In addition, we will address how LC3B and Atg5 up-regulation during autophagy can be examined through immunostaining in treated tumors and the potential of these proteins for use as surrogate markers to monitor therapeutic effects in clinical trials. Finally, we will discuss the challenges of studying autophagy in gliomas and the future directions of such use.

Adenovirus's last trick: you say lysis, we say autophagy.

The last stage of the adenovirus replication cycle, lysis, is considered not very efficient and remains poorly understood. Pathogen infection induces autophagy in eukaryotic cells. In the case of viruses, autophagy is a double-edged sword that can either facilitate or impede replication. On one hand, autophagy reduces the replication capability of the herpesviruses. On the other hand, the RNA virus poliovirus uses autophagosomes to form replication complexes. Recently we characterized the autophagy induced by the oncolytic adenovirus Delta-24-RGD in brain tumor stem cells. Late in the adenoviral infectious cycle, we observed remarkable upregulation of the Atg12-Atg5 complex and prominent autophagy. In addition, adenovirus-induced autophagy results in disruption of the cytoplasmic structure and the continuity of the cellular membrane. We speculate that adenoviruses induce autophagy to facilitate the release of viral progeny at the end of the infectious cycle. The substitution of 'autophagy' for 'lysis' is not just semantic. Because autophagy is a genetically programmed process and not a passive phenomenon, it immediately suggests interactions between adenovirus proteins and autophagy regulators. Understanding the mechanism underlying adenovirus-mediated autophagy should propel the development of novel vectors with enhanced capability to release viral progeny and, as a result, morepotent oncolytic effect.