Salmonella are able to modulate host cell functions facilitating both uptake
and resistance to cellular host defence mechanisms. While interactions between
bacterial modulators and cellular proteins have been the main focus of
Salmonella research, relatively little is known about mammalian gene
regulation in response to Salmonella infection. A major class of mammalian
gene modulators consists of microRNAs. For our study we examined interactions
of microRNAs and regulated mRNAs in mammalian intestinal Salmonella infections
using a piglet model. After performing microRNA as well as mRNA specific
microarray analysis of ileal samples from Salmonella infected as well as
control piglets, we integrated expression analysis with target prediction
identifying microRNAs that mainly regulate focal adhesion as well as actin
cytoskeleton pathways. Particular attention was given to miR-29a, which was
involved in most interactions including Caveolin 2. RT-qPCR experiments
verified up-regulation of miR-29a after infection while its predicted target
Caveolin 2 was significantly down-regulated as examined by transcript and
protein detection. Reporter gene assays as well as RNAi experiments confirmed
Caveolin 2 to be a miR-29a target. Knock-down of Caveolin 2 in intestinal
epithelial cells resulted in retarded proliferation as well as increased
bacterial uptake. In addition, our experiments showed that Caveolin 2
regulates the activation of the small Rho GTPase CDC42 but apparently not RAC1
in human intestinal cells. Our study outlines for the first time important
regulation pathways in intestinal Salmonella infection pointing out that focal
adhesion and organisation of actin cytoskeleton are regulated by microRNAs.
Functional relevance is shown by miR-29a mediated Caveolin 2 regulation,
modulating the activation state of CDC42. Further analysis of examined
interactions may support the discovery of novel strategies impairing the
uptake of intracellular pathogens