Abstract:Salmonella Typhimurium is an intracellular pathogen that causes gastroenteritis in humans. Aided by a battery of effector proteins, S. Typhimurium resides intracellularly in a specialized vesicle, called the Salmonella-containing vacuole (SCV) that utilizes the host endocytic vesicular transport pathway (VTP). Here, we probed the possible role of SUMOylation, a post-translation modification pathway, in SCV biology. Proteome analysis by complex massspectrometry (MS/MS) revealed a dramatically altered SUMOproteo… Show more
“…26) Rab7 is a critical regulator of the assembly of Salmonella-containing vacuoles, where the bacterium proliferates and is thus, intimately involved in infection. 27,28) Mycobacterium avium preferentially infects enterocytes. Infants are more susceptible to bacterial infection.…”
Enterocytes in neonatal rodent endocytose milk materials as macromolecule and digest them into small nutrient molecules. Bulk endocytic membrane flow sustaining nutrient uptake inevitably brings the plasma membrane into large lysosomes, as known as supranuclear vesicles or apical vacuoles which exhibit a unique morphology in infant enterocytes. Endocytic delivery to the large vacuoles required the function of Rab7 GTPase. The Rab7-deficient neonatal enterocytes became filled with abnormal gigantic vacuoles as they migrated from the intervillus pocket to the distal region of the villi and they became defective in taking up macromolecules. Infant animals lacking Rab7 in enterocytes exhibited growth retardation. These results showed that the Rab7-dependent endocytic pathways play an important role in nutrient absorption during pre-weaning growth.
“…26) Rab7 is a critical regulator of the assembly of Salmonella-containing vacuoles, where the bacterium proliferates and is thus, intimately involved in infection. 27,28) Mycobacterium avium preferentially infects enterocytes. Infants are more susceptible to bacterial infection.…”
Enterocytes in neonatal rodent endocytose milk materials as macromolecule and digest them into small nutrient molecules. Bulk endocytic membrane flow sustaining nutrient uptake inevitably brings the plasma membrane into large lysosomes, as known as supranuclear vesicles or apical vacuoles which exhibit a unique morphology in infant enterocytes. Endocytic delivery to the large vacuoles required the function of Rab7 GTPase. The Rab7-deficient neonatal enterocytes became filled with abnormal gigantic vacuoles as they migrated from the intervillus pocket to the distal region of the villi and they became defective in taking up macromolecules. Infant animals lacking Rab7 in enterocytes exhibited growth retardation. These results showed that the Rab7-dependent endocytic pathways play an important role in nutrient absorption during pre-weaning growth.
“…DeSUMOylation caused by L. monocytogenes inhibits TGF beta signaling, while S. flexneri-induced deSUMOylation increases permeability of the gut, favoring bacterial invasion and induces an exacerbated inflammatory response in mice [20]. Intracellular S. typhimurium reduces Rab7 SUMOylation and favors the formation of Salmonellainduced membrane filaments radiating from the Salmonella-containing vacuole which improves bacteria survival [21]. Finally, two protozoan parasites, which also live in parasitophorous vacuoles, Plasmodium berghei and Toxoplasma gondii, reduce protein SUMOylation to inhibit nuclear translocation of immune induced transcription factors, such as SMAD4, thereby reducing cellular responses to infection, resisting apoptosis, and favoring parasite infection [39].…”
Leishmania parasites use elaborate virulence mechanisms to invade and thrive in macrophages. These virulence mechanisms inhibit host cell defense responses and generate a specialized replicative niche, the parasitophorous vacuole. In this work, we performed a genome-wide RNAi screen in Drosophila macrophage-like cells to identify host factors necessary for Leishmania amazonensis infection. This screen identified 52 conserved genes required specifically for parasite entry, including several components of the SUMOylation machinery. Further studies in mammalian macrophages found that L. amazonensis infection inhibited SUMOylation within infected macrophages and this inhibition enhanced parasitophorous vacuole growth and parasite proliferation through modulation of multiple genes especially ATP6V0D2, which in turn effects CD36 expression and cholesterol levels. Together, these data suggest that parasites actively sabotage host SUMOylation and alter host transcription to improve their intracellular niche and enhance their replication.
“…However itself, it is not degraded by autophagy (Kumar et al, 2018;Mehto et al, 2019). This is not surprising as several of the core autophagy proteins such as ULK1, ATG16L1, ATG12 (Haller et al, 2014;Nazio et al, 2016;Scrivo et al, 2019) and endolysosomal trafficking proteins such as RAB7A (Mohapatra et al, 2019), which facilitates autophagic degradation of cargo proteins but themselves are not degraded by the autophagy.…”
Activation of the type 1 interferon response is extensively connected to the pathogenesis of autoimmune diseases. Loss of function of Immunity Related GTPase M (IRGM) has also been associated to several autoimmune diseases, but its mechanism of action is unknown. Here, we found that IRGM is a master negative regulator of the interferon response. Several nucleic acid‐sensing pathways leading to interferon‐stimulated gene expression are highly activated in IRGM knockout mice and human cells. Mechanistically, we show that IRGM interacts with nucleic acid sensor proteins, including cGAS and RIG‐I, and mediates their p62‐dependent autophagic degradation to restrain interferon signaling. Further, IRGM deficiency results in defective mitophagy leading to the accumulation of defunct leaky mitochondria that release cytosolic DAMPs and mtROS. Hence, IRGM deficiency increases not only the levels of the sensors, but also those of the stimuli that trigger the activation of the cGAS‐STING and RIG‐I‐MAVS signaling axes, leading to robust induction of IFN responses. Taken together, this study defines the molecular mechanisms by which IRGM maintains interferon homeostasis and protects from autoimmune diseases.
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