genomewide characterization of host-pathogen interactions by ...

Maren Depke
Results
Host Cell Gene Expression Pattern in an in vitro Infection Model
Insights into infection-dependent differential gene expression by selected examples from the
6.5 h time point
Infection of S9 cells with S. aureus RN1HG and internalization of the pathogen affected
metabolism related genes 6.5 h after start of infection.
Interestingly, the second most strongly induced gene was indoleamine 2,3-dioxygenase 1
(IDO1, fold change 23.5), a key molecule in immunomodulation, microbial growth control, and
pathogen immune escape (Zelante et al. 2009). The enzyme catalyzes the reaction of tryptophan
to formylkynurenine. In relation to IDO1, the increased expression of WARS (4.4) whose gene
product is responsible for tryptophan tRNA charging attracted attention.
Lipid metabolism related genes regulated 6.5 h after start of infection in S9 cells featured a
decreased expression in infected samples leading to the assumption of a reduced de novo
lipogenesis (Fig. R.4.10).
This concerned different types of lipids. In the mevalonate pathway and the following
cholesterol biosynthesis steps, five genes were repressed: mevalonate kinase (MVK; −2.2),
farnesyl-diphosphate farnesyltransferase 1 (FDFT1; −1.7), sterol-C4-methyl oxidase-like (SC4MOL;
−2.0), squalene epoxidase (SQLE; −1.8) and NAD(P) dependent steroid dehydrogenase-like
(NSDHL; −1.7). The induced genes of cholesterol 25-hydroxylase (CH25H; 6.0) and oxysterol
binding protein-like 10 (OSBPL10; 1.8) are involved in negative feedback on cholesterol
biosysnthesis. The repression of fatty acid synthase (FASN; −1.7) is linked to two genes indirectly
involved in lipid metabolism. Deiodinase type II (DIO2; −4.1) catalyzes the deiodization of
thyroxine (T 4 ) to the main biologically active form triiodothyronine (T 3 ), which is known to induce
lipogenesis. Although there was probably no hormone T 4 to be converted in the in vitro situation
used for this study, the repression of DIO2 might reflect a reaction that makes sense in vivo for
bronchial epithelial cells leading to less local activation of lipogenesis. In contrast, glucagon (GCG)
is known to suppress lipogenesis (Hillgartner et al. 1995). This hormone was induced (3.6) in
infected S9 cells. Finally, the two genes for mitochondrial glycerol-3-phosphate acyltransferase
(GPAM; −1.6) and 1-acylglycerol-3-phosphate O-acyltransferase 5 (AGPAT5; −1.5), which are
involved in triacylglycerol biosynthesis, were repressed in infected samples.
Fig. R.4.10:
Repression of enzyme genes related to
lipid metabolism.
Lipid metabolism related genes were
chosen with the help of omics-viewer(s)
of BIOCYC (SRI International, CA, USA,
http://biocyc.org) and manually added
to and arranged in the Ingenuity
Pathway Analysis path designer tool
(IPA, www.ingenuity.com). Green color
indicates repression of gene expression
in infected samples at the 6.5 h time
point, red color induction of gene
expression, and more intense color
shows a higher absolute fold change.
Enzymes mevalonate kinase (MVK),
farnesyl-diphosphate farnesyltransferase
1 (FDFT1) in mevalonate
pathway, and sterol-C4-methyl oxidaselike
(SC4MOL), SQLE (squalene
epoxidase), and NAD(P) dependent steroid dehydrogenase-like (NSDHL) in the following steps of cholesterol biosynthesis were
repressed. CH25H (cholesterol 25-hydroxylase) and OSBPL10 (oxysterol binding protein-like 10), which are involved in negative
feedback on cholesterol biosynthesis, were induced. Fatty acid synthase (FASN), the enzyme of fatty acid biosynthesis, was repressed,
and also deiodinase type II (DIO2), an enzyme catalyzing the deiodization of thyroxine (T 4) to the main biologically active form
triiodothyronine (T 3). T 3 induces (A) de novo lipogenesis, while glucagon (GCG) suppresses (I) it. The enzymes mitochondrial glycerol-3-
phosphate acyltransferase (GPAM) and 1-acylglycerol-3-phosphate O-acyltransferase 5 (AGPAT5) are involved in triacylglycerol
biosynthesis. Their expression was reduced 6.5 h after start of infection.
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