Abstract
The enterobacterium, Klebsiella pneumoniae invades the intestinal epithelium of humans by interfering with multiple host cell response. To uncover a system-level overview of host response during infection, we analyzed the global dynamics of protein profiling in Caenorhabditis elegans using quantitative proteomics approach. Comparison of protein samples of nematodes exposed to K. pneumoniae for 12, 24, and 36 h by 2DE revealed several changes in host proteome. A total of 266 host-encoded proteins were identified by 2DE MALDI-MS/MS and LC-MS/MS and the interacting partners of the identified proteins were predicted by STRING 10.0 analysis. In order to understand the interacting partners of regulatory proteins with similar or close pI ranges, a liquid IEF was performed and the isolated fractions containing proteins were identified by LC-MS/MS. Functional bioinformatics analysis on identified proteins deciphered that they were mostly related to the metabolism, dauer formation, apoptosis, endocytosis, signal transduction, translation, developmental, and reproduction process. Gene enrichment analysis suggested that the metabolic process as the most overrepresented pathway regulated against K. pneumoniae infection. The dauer-like formation in infected C. elegans along with intestinal atrophy and ROS during the physiological analysis indicated that the regulation of metabolic pathway is probably through the involvement of mTOR. Immunoblot analysis supported the above notion that the K. pneumoniae infection induced protein mis-folding in host by involving PI3Kinase/AKT-1/mTOR mediated pathway. Furthermore, the susceptibility of pdi-2, akt-1, and mTOR C. elegans mutants confirmed the role and involvement of PI3K/AKT/mTOR pathway in mediating protein mis-folding which appear to be translating the vulnerability of host defense toward K. pneumoniae infection.
Highlights
Infection by Klebsiella pneumoniae is one of the most significant problems facing human health
We identified several stress responsive, detoxification, and protein mis-folding genes strongly induced after K. pneumoniae infection
The C. elegans, which is devoid of lungs system, has globally been accepted as a suitable model (Singh and Aballay, 2006; Akira, 2009) to study host response against lung and respiratory tract infecting microorganisms such as P. aeruginosa (Tan et al, 1999; Kirienko et al, 2013; Balasubramanian et al, 2016), Streptococcus pneumoniae (Bolm et al, 2004), Streptococcus pyogens (Jansen et al, 2002), Microbacterium Spp. (Hodgkin et al, 2000), Mycoplasma iowae (Pritchard et al, 2014), S. aureus (Bogaerts et al, 2010a; JebaMercy et al, 2011), FIGURE 9 | (A) The western blot analysis showing the regulation of upstream regulators of mTOR in C. elegans at different time points (12, 24, and 36 h)
Summary
Infection by Klebsiella pneumoniae is one of the most significant problems facing human health. Several necessary measures have been taken to control the infections caused by K. pneumoniae, the emergence of new drug-resistance superbugs poses a great level of threat. Insightful knowledge on how pathogen alters the host cellular immune defense using a eukaryotic model organism may potentially open a new avenue for therapeutic interventions. It has been considered that not all outcomes of pre-clinical studies using model animals could be effectively extrapolated to humans (Fuchs et al, 2009; Evans et al, 2010). There are several mammalian models with diversified physiological, anatomical, molecular, and genetic characteristics have comprehensively been utilized to understand host-pathogen interactions as well as in pre-clinical assessment of drugs (Means and Aballay, 2011). Numerous reports have argued the extensive use of several alternative models such as insects, small vertebrates, and nematodes for studying bacterial infections (Kurz and Ewbank, 2007; Lopez Hernandez et al, 2015)
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