Vision of LIFE - Volume 17 - No. 1

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How does the Zika virus work?
As of May 2015, there has been a large Zika epidemic in the Americas and the Pacific. Ever
since then, there has been increased research of the Zika virus. Researches say that the Zika
virus causes microcephaly to the unborn child. Jae Jung from the University of Southern
California reported in Cell Stem Cell that 2 of the 10 proteins that are produced by the Zika
virus cause microcephaly. These two proteins, NS4A and NS4B, prevent the phosphorylation
of two amino acids in the Akt protein by mTOR. This leads to inhibition of the signalling
pathway of Akt-mTOR. Akt without phosphorylation is inactive, meaning it cannot activate
the proteins normally regulating the cell’s autophagy, thus, random autophagy occurs. This
means infected cells digest their own organelles without any form of control. The energy and
nutrients that come free in this digestive process are used by the virus. The signalling pathway
of Akt-mTOR is very important for the growth of neurons in the brain of the unborn baby. It
is likely that the Zika virus’ inhibition of the signalling Akt-mTOR pathway leading to random
autophagy destroy so much of the cell’s compartments that neurons die, disabling the brain’s
growth. It would be reasonable to think that medicines are being developed inhibiting the
production of NS4A and NS4B, but unfortunately there is no medicine yet.
Source; C2W (2016). Wat zika met embryo’s doet. C2W life sciences 15, 09-09-2016, 17.
Jung, J.U. et al. (2016). Zika Virus NS4A and NS4B Proteins Deregulate Akt-mTOR Signaling in Human Fetal Neural Stem Cells to
Inhibit Neurogenesis and Induce Autophagy. Cell Stem Cell, 11-08-2016.
Figure 2. Monocercomonas sp.
Eukaryotes without mitochondria
Most people learn at school – or in college – that all
eukaryotes have mitochondria. But that ground rule of cell
biology has recently been proven wrong. Czech researchers
discovered a single-cell organism in the guts of a chinchilla
that does not contain mitochondria. This organism, part
of the genus Monocercomonoides, is an oxymonad, living
a parasite life. It was already known that oxymonads have
unusual mitochondria, since they do not need mitochondria
for their energy supply, as they are anaerobe organisms and
mitochondria use oxygen. When the researchers sequenced
the DNA of the Monocercomonas sp. they were unable to
find any sign of typical mitochondrial DNA or mitochondrial
proteins. It is likely that other proteins take over the functions
of the mitochondria, because these single-cell organisms have
copied DNA from bacteria that do not contain mitochondria
either. According to the researchers, the most logical explanation of this phenomenon is
that all mitochondria are evolved out of the eukaryote’s genome: there is simply no need for
them, so it is more efficient to dispose of them completely. Another explanation is that the
mitochondrial proteins are so well evolved that they cannot be recognised. However, the Czech
researchers think that this is extremely unlikely, as mitochondrial proteins normally do not
evolve at such speeds.
Science
Source; C2W (2016). Kijk mama, zonder mitochondriën. C2W life sciences 11, 06-17-2016, 7.
Job Deen