The ins-and-outs of exosome biogenesis, secretion, and internalization.

Exosomes are specialized cargo delivery vesicles secreted from cells by fusion of multivesicular bodies (MVBs) with the plasma membrane (PM). While the function of exosomes during physiological and pathological events has been extensively reported, there remains a lack of understanding of the mechanisms that regulate exosome biogenesis, secretion, and internalization. Recent technological and methodological advances now provide details about MVB/exosome structure as well as the pathways of exosome biogenesis, secretion, and uptake.

Ceramide-rich microdomains facilitate nuclear envelope budding for non-conventional exosome formation.

Neutrophils migrating towards chemoattractant gradients amplify their recruitment range by releasing the secondary chemoattractant leukotriene B (LTB) refs. . We previously demonstrated that LTB and its synthesizing enzymes, 5-lipoxygenase (5-LO), 5-LO activating protein (FLAP) and leukotriene A hydrolase, are packaged and released in exosomes.

Exosomes mediate LTB4 release during neutrophil chemotaxis.

Leukotriene B4 (LTB4) is secreted by chemotactic neutrophils, forming a secondary gradient that amplifies the reach of primary chemoattractants. This strategy increases the recruitment range for neutrophils and is important during inflammation. Here, we show that LTB4 and its synthesizing enzymes localize to intracellular multivesicular bodies, which, upon stimulation, release their content as exosomes.

Method for Studying the Effect of Gene Silencing on Bacterial Infection-induced ERK1/2 Signaling in Bone-marrow Derived Macrophages.

Macrophages are highly phagocytic cells that utilize various pathogen recognition receptors (PRRs) to recognize pathogen-associated molecular patterns (PAMPs). These PAMPs can be present within the microbe, such as bacterial CpG DNA, and are recognized by Toll-like receptor 9 (TLR9), a PRR present on the endosomal membrane of macrophages. PAMPs can also be present on the surface of microbes, such as Lipopolysaccharide (LPS), which decorates the outer membrane of gram-negative bacteria like and .

ARL11 regulates lipopolysaccharide-stimulated macrophage activation by promoting mitogen-activated protein kinase (MAPK) signaling.

DP-ibosylation factor-ike GTPase () is a cancer-predisposing gene that has remained functionally uncharacterized to date. In this study, we report that ARL11 is endogenously expressed in mouse and human macrophages and regulates their activation in response to lipopolysaccharide (LPS) stimulation. Accordingly, depletion of ARL11 impaired both LPS-stimulated pro-inflammatory cytokine production by macrophages and their ability to control intracellular replication of LPS-stimulated activation of extracellular signal-regulated kinase (ERK) and p38 mitogen-activated protein kinase (MAPK) was substantially compromised in -silenced macrophages.

Salmonella exploits the host endolysosomal tethering factor HOPS complex to promote its intravacuolar replication.

Salmonella enterica serovar typhimurium extensively remodels the host late endocytic compartments to establish its vacuolar niche within the host cells conducive for its replication, also known as the Salmonella-containing vacuole (SCV). By maintaining a prolonged interaction with late endosomes and lysosomes of the host cells in the form of interconnected network of tubules (Salmonella-induced filaments or SIFs), Salmonella gains access to both membrane and fluid-phase cargo from these compartments. This is essential for maintaining SCV membrane integrity and for bacterial intravacuolar nutrition.

The Rab7 effector PLEKHM1 binds Arl8b to promote cargo traffic to lysosomes.

Endocytic, autophagic, and phagocytic vesicles move on microtubule tracks to fuse with lysosomes. Small GTPases, such as Rab7 and Arl8b, recruit their downstream effectors to mediate this transport and fusion. However, the potential cross talk between these two GTPases is unclear.