and M.B. Endosomes in Exosome-Treated Huh7 Cells, Linked to Shape?4 z-stacked merged images of Endo-GFP-expressing Huh7 cells treated with exosomes and stained for gp63 were captured with an ANDOR Spinning Disc Confocal microscope and processed with Nikon NIS Element AR 3.2 software to get the 3D view of the cells. The 3D rotational views were captured at a rate of 30 frames/sec to create the movie. Endo-GFP is in green and Diosgenin gp63 is in red. DAPI was used to stain the nucleus. mmc3.jpg (63K) GUID:?C87B3188-2CDB-467A-9135-15DE0A273D21 Summary causes visceral leishmaniasis (VL) where the parasite infects and resides inside liver and spleen tissue macrophages. Given the abnormal lipid profile observed in VL patients, we examined the status of serum lipids in an experimental murine model of VL. The murine VL liver displayed altered expression of lipid metabolic genes, many of which are direct or indirect targets of the liver-specific microRNA-122. Concomitant reduction of miR-122 expression was observed in VL liver. High serum cholesterol caused resistance to infection, while downregulation of miR-122 is coupled with low serum cholesterol in VL mice. Exosomes secreted by the infective parasites caused reduction in miR-122 activity in hepatic cells. surface glycoprotein Rabbit Polyclonal to MERTK gp63, a Zn-metalloprotease, targets pre-miRNA processor Dicer1 to prevent miRNP formation in infection reduces liver miR-122 and lowers serum cholesterol ? metalloprotease gp63 is required for inhibition of hepatic miR-122 activity ? gp63 cleaves DICER1 to downregulate miRNP-122 formation in hepatocytes ? Restoration of miR-122 elevates serum cholesterol to reduce liver parasite load Introduction Visceral leishmaniasis (VL) is caused by the protozoan parasite or and is the most fatal form of this parasitic disorder (Murray et?al., 2005). The parasite infects the spleen and Diosgenin liver of infected individuals and resides within the macrophages to escape host immune response (Olivier et?al., 2005) It shows a dimorphic life cycle, residing as flagellate promastigotes in the midgut of the sand fly vector and as aflagellate amastigotes in the mammalian host (Desjardins and Descoteaux, 1998; Engwerda et?al., 2004). Liver is the primary organ that gets infected in the early phase of infection where the parasites survive within the tissue macrophage Kpffer cells, while the liver parenchyma remains noninfected (Beattie et?al., 2010). VL patients Diosgenin show hypolipidemia characterized by reduced serum total cholesterol and lipoproteins (Lal et?al., 2007). Interestingly, hyperlipidemia is associated with resistance to VL (Ghosh et?al., 2012). In experimental VL, reduced membrane cholesterol in infected macrophages leads to increased membrane fluidity affecting its antigen-presenting ability (Chakraborty et?al., 2005). Liposomal formulation of cholesterol is known to offer protection in infected hamsters (Banerjee et?al., 2009). Although the involvement of cholesterol in controlling VL is evident from these studies, little is known about the influence of on host lipid metabolism. MicroRNAs (miRNAs), the 20C22 nt long posttranscriptional regulators, mediate gene repression primarily by inducing translational repression or degradation of target mRNAs to affect almost all physiological processes including metabolic processes in higher eukaryotes (Filipowicz et?al., 2008; Krtzfeldt and Stoffel, 2006). Precursors to miRNAs, primary miRNA transcripts (pri-miRNAs) are processed by microprocessor Drosha-DGCR8 in the nucleus to generate precursor miRNAs (pre-miRNAs), which are subsequently processed to the mature form by RNase III endonuclease Dicer1 in the cytoplasm (Filipowicz et?al., 2008). The miRNA encoding strand of miRNA duplex gets loaded to Argonaute proteins by DICER1 and TAR RNA-binding proteins (TRBPs) to form active microRNA ribonucleoprotein complexes (miRNPs). miR-122, a miRNA expressed abundantly in liver, modulates a wide range of liver functions. miR-122 comprises more than 70% of the liver miRNA pool and is largely responsible for liver homeostasis and lipid metabolism (Chang et?al., 2004; Girard et?al., 2008). Antisense oligonucleotides against miR-122 confirmed its role in fatty acid and cholesterol metabolism (Elmn et?al., 2008; Esau et?al., 2006). Therefore, it is an interesting possibility that parasite infection controls liver miR-122 in order to modulate serum cholesterol. interacts with its target cell either by cell-cell contact or by secreting exosomes containing virulence factors (Silverman et?al., 2010). The surface metalloprotease gp63,?a membrane-bound glycosylphosphatidylinositol (GPI)-anchored glycoprotein of 63?kDa, is a known virulence factor present in exosomes that serves as a ligand for the macrophage complement receptor (Brittingham et?al., 1995). This surface protease cleaves multiple intracellular proteins and participates in p38 mitogen-activated protein (MAP) kinase inactivation (Hall et?al., 2009). gp63 is also responsible for selective degradation of eIF4E in infection downregulates miR-122 and genes involved in cholesterol biosynthesis in infected mouse livers to reduce serum cholesterol. We have also found that restoration of miR-122 induces revival of serum cholesterol.