The ESCRT machinery is not required for human cytomegalovirus envelopment.

The human cytomegalovirus (HCMV) has been proposed to complete its final envelopment on cytoplasmic membranes prior to its release to the extracellular medium. The nature of these membranes and the mechanisms involved in virus envelopment and release are poorly understood. Here we show by immunogold-labelling and electron microscopy that CD63, a marker of multivesicular bodies (MVBs), is incorporated into the viral envelope, supporting the notion that HCMV uses endocytic membranes for its envelopment. We therefore investigated a possible role for the cellular endosomal sorting complex required for transport (ESCRT) machinery in HCMV envelopment. Depletion of tumour suppressor gene 101 and ALIX/AIP1 with small interfering RNAs (siRNAs) in HCMV-infected cells did not affect virus production. In contrast, siRNAs against the vacuolar protein sorting 4 (VPS4) proteins silenced the expression of VPS4A and VPS4B, inhibited the sorting of epidermal growth factor to lysosomes, the formation of HIV Gag-derived virus-like particles and vesicular stomatitis virus infection, but enhanced the number of HCMV viral particles produced. Treatment of infected cells with protease inhibitors also increased viral production. These studies indicate that, in contrast to some enveloped RNA viruses, HCMV does not require the cellular ESCRT machinery to complete its envelopment.

Interaction between Alzheimer's Abeta1-42 peptide and DNA detected by surface plasmon resonance.

Alzheimer's disease is a form of senile mental disorder characterized by the presence of extracellular plaques, containing amyloid-beta (Abeta) as the main component. According to the amyloid hypothesis, an increase of extracellular Abeta production is in the origin of the aberrant plaques causing neuronal loss and dementia. However, a wealth of evidence has been accumulated pointing to the toxicity of soluble intracellular Abeta, having different morphologies of aggregation, as the origin of the neurodegenerative process. The exact nature of the initial molecular events by which Abeta exerts its neurotoxicity, remains obscure. Different forms of soluble Abeta peptide aggregates have been recently found to reside in the nucleus of CHO cells and Alzheimer's disease brain samples. This paper focus mainly on the interaction between DNA and the 42 residue Abeta (Abeta42) as studied by Surface Plasmon Resonance. Electronic microscopy and UV-visible spectroscopy are also used to further characterize the interaction. Particular attention is paid to the extent of Abeta42 aggregation needed to observe the interaction with DNA. Our results show that DNA binds all soluble aggregate forms of Abeta42, therefore suggesting that DNA binding is a general property of different soluble forms of Abeta42, unrelated to the extent of aggregation.

Mycoplasma pneumoniae: a reduced-genome intracellular bacterial pathogen.

Mycoplasma pneumoniae has classically been considered an extracellular (or membrane-associated) organism. Nevertheless, the recently elucidated genomic structure of this pathogen strongly suggest that this organism may have been subjected to the process of reductive genetic evolution which is characteristic of intracellular bacteria. We studied the Mycoplasma pneumoniae RYC15989 strain, recovered from a pericardial biopsy sample from a patient with atypical pneumonia and acute pericarditis. The interaction of this strain with human hepatocytes Hep-G2 and mouse neuroblastoma N2-A cell lines was investigated. Confocal laser scanning microscopy and electronic microscopy evidence is presented of the intracellular location of fluorochrome-labelled Mycoplasma pneumoniae in cell lines infected with the organism in vitro. This finding provides preliminary evidence of cellular invasive capacity of Mycoplasma pneumoniae and casts some new light on the pathogenic potential of Mycoplasma pneumoniae in host infection.