https://gene-quantification.de/simons-raposo-exosome-communication-2009.pdf

Exosomes--vesicular carriers for intercellular communication.

Lysosomes are the primary catabolic compartments of eukaryotic cells. They degrade extracellular material that has been internalized by endocytosis and intracellular components that have been sequestered by autophagy. In addition, specialized cells contain lysosome-related organelles that store and secrete proteins for cell-type-specific functions. The functioning of a healthy cell is dependent on the proper targeting of newly synthesized lysosomal proteins. Accumulating evidence suggests that there are multiple lysosomal delivery pathways that together allow the regulated and sequential deposition of lysosomal components. The importance of lysosomal trafficking pathways is emphasized by recent findings that reveal new roles for lysosomal membrane proteins in cellular physiology and in an increasing number of diseases that are characterized by defects in lysosome biogenesis.

Lysosome biogenesis and lysosomal membrane proteins: trafficking meets function

Oligodendrocytes secrete vesicles into the extracellular space, where they might play a role in neuron-glia communication. These exosomes are small vesicles with a diameter of 50-100 nm that are formed within multivesicular bodies and are released after fusion with the plasma membrane. The intracellular pathways that generate exosomes are poorly defined. Because Rab family guanosine triphosphatases (GTPases) together with their regulators are important membrane trafficking organizers, we investigated which Rab GTPase-activating proteins interfere with exosome release. We find that TBC1D10A-C regulate exosome secretion in a catalytic activity-dependent manner. We show that Rab35 is the target of TBC1D10A-C and that the inhibition of Rab35 function leads to intracellular accumulation of endosomal vesicles and impairs exosome secretion. Rab35 localizes to the surface of oligodendroglia in a GTP-dependent manner, where it increases the density of vesicles, suggesting a function in docking or tethering. These findings provide a basis for understanding the biogenesis and function of exosomes in the central nervous system.

/pdf/regulation-of-exosome-secretion-by-rab35-and-its-gtpase-1s13e76dhk.pdf

Regulation of exosome secretion by Rab35 and its GTPase-activating proteins TBC1D10A–C

Lysosomes are ubiquitous membrane-bound intracellular organelles with an acidic interior. They are central for degradation and recycling of macromolecules delivered by endocytosis, phagocytosis, and autophagy. In contrast to the rather simplified view of lysosomes as waste bags, nowadays lysosomes are recognized as advanced organelles involved in many cellular processes and are considered crucial regulators of cell homeostasis. The function of lysosomes is critically dependent on soluble lysosomal hydrolases (e.g. cathepsins) as well as lysosomal membrane proteins (e.g. lysosome-associated membrane proteins). This review focuses on lysosomal involvement in digestion of intra- and extracellular material, plasma membrane repair, cholesterol homeostasis, and cell death. Regulation of lysosomal biogenesis and function via the transcription factor EB (TFEB) will also be discussed. In addition, lysosomal contribution to diseases, including lysosomal storage disorders, neurodegenerative disorders, cancer, and cardiovascular diseases, is presented.

/pdf/the-lysosome-from-waste-bag-to-potential-therapeutic-target-2zxxln3iio.pdf

The lysosome: from waste bag to potential therapeutic target

https://biblio.ugent.be/publication/5686680/file/5686770.pdf

Understanding ultrasound induced sonoporation: Definitions and underlying mechanisms ☆

Ca2+ influx through plasma membrane lesions triggers a rapid repair process that was previously shown to require the exocytosis of lysosomal organelles (Reddy, A., E. Caler, and N. Andrews. 2001. Cell. 106:157-169). However, how exocytosis leads to membrane resealing has remained obscure, particularly for stable lesions caused by pore-forming proteins. In this study, we show that Ca2+-dependent resealing after permeabilization with the bacterial toxin streptolysin O (SLO) requires endocytosis via a novel pathway that removes SLO-containing pores from the plasma membrane. We also find that endocytosis is similarly required to repair lesions formed in mechanically wounded cells. Inhibition of lesion endocytosis (by sterol depletion) inhibits repair, whereas enhancement of endocytosis through disruption of the actin cytoskeleton facilitates resealing. Thus, endocytosis promotes wound resealing by removing lesions from the plasma membrane. These findings provide an important new insight into how cells protect themselves not only from mechanical injury but also from microbial toxins and pore-forming proteins produced by the immune system.

https://rupress.org/jcb/article-pdf/180/5/905/1335604/jcb_200708010.pdf

Repair of injured plasma membrane by rapid Ca2+-dependent endocytosis

Rapid plasma membrane resealing is essential for cellular survival. Earlier studies showed that plasma membrane repair requires Ca2+-dependent exocytosis of lysosomes and a rapid form of endocytosis that removes membrane lesions. However, the functional relationship between lysosomal exocytosis and the rapid endocytosis that follows membrane injury is unknown. In this study, we show that the lysosomal enzyme acid sphingomyelinase (ASM) is released extracellularly when cells are wounded in the presence of Ca2+. ASM-deficient cells, including human cells from Niemann-Pick type A (NPA) patients, undergo lysosomal exocytosis after wounding but are defective in injury-dependent endocytosis and plasma membrane repair. Exogenously added recombinant human ASM restores endocytosis and resealing in ASM-depleted cells, suggesting that conversion of plasma membrane sphingomyelin to ceramide by this lysosomal enzyme promotes lesion internalization. These findings reveal a molecular mechanism for restoration of plasma membrane integrity through exocytosis of lysosomes and identify defective plasma membrane repair as a possible component of the severe pathology observed in NPA patients.

/pdf/exocytosis-of-acid-sphingomyelinase-by-wounded-cells-25hu1qd20y.pdf

Exocytosis of acid sphingomyelinase by wounded cells promotes endocytosis and plasma membrane repair.

Two-way traffic on the road to plasma membrane repair

Botulinum neurotoxin (BoNT) intoxication can lead to the disease botulism, characterized by flaccid muscle paralysis that can cause respiratory failure and death. Due to the significant morbidity and mortality costs associated with BoNTs high toxicity, developing highly sensitive, rapid, and field-deployable assays are critically important to protect the nation's food supply against either accidental or intentional contamination. We report here that the B-cell based biosensor assay CANARY® (Cellular Analysis and Notification of Antigen Risks and Yields) Zephyr detects BoNT/A holotoxin at limits of detection (LOD) of 10.0 ± 2.5 ng/mL in assay buffer. Milk matrices (whole milk, 2% milk and non-fat milk) with BoNT/A holotoxin were detected at similar levels (7.4⁻7.9 ng/mL). BoNT/A complex was positive in carrot, orange, and apple juices at LODs of 32.5⁻75.0 ng/mL. The detection of BoNT/A complex in solid complex foods (ground beef, smoked salmon, green bean baby puree) ranged from 14.8 ng/mL to 62.5 ng/mL. Detection of BoNT/A complex in the viscous liquid egg matrix required dilution in assay buffer and gave a LOD of 171.9 ± 64.7 ng/mL. These results show that the CANARY® Zephyr assay can be a highly useful qualitative tool in environmental and food safety surveillance programs.

A Rapid, Sensitive, and Portable Biosensor Assay for the Detection of Botulinum Neurotoxin Serotype A in Complex Food Matrices.

Brewer's spent grain (BSG) was dried via infra-red drying (IRD) or hot-air drying (HAD) and milled into fine powders. Proximate analysis (moisture, protein, fat, ash, carbohydrates by difference), water activity, dietary fiber, total soluble phenolics, and antioxidant capacity analyses were performed to characterize and compare both types of BSG powders. Mice feeding of the two types of dried BSG, each at three different concentrations, was conducted to compare the effects of the two types of dried BSG on health indicators and to determine evidence of dose response. Weights of body, feed intake, adipose tissue, kidney, and liver were recorded; blood plasma, cholesterol, liver fat, and fecal fat and protein were also measured. Significant differences were observed for liver and adipose tissue, cholesterol, and fecal protein between mice fed diets with different concentrations of BSG compared to the control diet. The analysis of hormones related to type II diabetes and metabolic syndrome did not show differences between the hormones examined, except for ghrelin and leptin, which are directly correlated with increased white adipose tissue in mice consuming high fat diets. No differences in health indicators were found in mice fed with the two different types of BSG. Mice fed with HAD and IRD BSG diets increased the relative abundance of Firmicutes and Bacteroidetes phylum microbiota compared to control diet, with no differences due to the type and concentrations of BSG in mice diets. The present results suggest that increasing levels of BSG incorporated into human foods may impart health benefits. 

Christina Tam

Papers

Repair of injured plasma membrane by rapid Ca2+-dependent endocytosis

Exocytosis of acid sphingomyelinase by wounded cells promotes endocytosis and plasma membrane repair.

Two-way traffic on the road to plasma membrane repair

A Rapid, Sensitive, and Portable Biosensor Assay for the Detection of Botulinum Neurotoxin Serotype A in Complex Food Matrices.

Influence of drying methods on health indicators of brewers spent grain for potential upcycling into food products