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Atherosclerosis
Published in George Feuer, Felix A. de la Iglesia, Molecular Biochemistry of Human Disease, 2020
George Feuer, Felix A. de la Iglesia
The vascular endothelium is permeable to a wide range of molecules. The permeability of the endothelium involves the presence of a pore system and the vesicular transport. Physiological studies on capillary transport revealed the existence of a two-pore system, one with small pores of approximately 9 μm in diameter and the other with large pores about 50 μm in diameter. Molecules up to 500,000 Da cross the endothelium by vesicular transport. The vesicular transport is bidirectional or emits invaginations on the luminal plasma membrane. LDL of about 22 μm in diameter can move across the normal endothelium in pinocytotic vesicles. This type of transport is unlikely for the larger chylomicrons and intact VLDL molecules.568 Albumin and fibrinogen cross the arterial endothelium, and there are focal and regional differences in the permeability to these macromolecules.
Structural Organization of the Liver
Published in Robert G. Meeks, Steadman D. Harrison, Richard J. Bull, Hepatotoxicology, 2020
As mentioned above, proteins and lipoproteins are transported through the hepatocytes via membrane-bound vesicles and excreted into the blood. Vesicular transport is also involved in the endocytosis, intracellular transport, and exocytosis of a variety of other substances. Certain macromolecules are internalized specifically by receptor-medicated endocytosis, which differs from nonspecific fluid phase pinocytosis in that it involves binding of the ligand to be internalized to a specific receptor on the surface of the cell. Because endocytosis involves the formation of vesicles containing the ligand through pinching off from the plasma membrane, the ligand remains segregated from the cytoplasma by the surrounding vesicular membrane. Therefore, endocytosis differs from carrier-mediated transport systems, by catalizing the movement of small polar molecules and ions directly across the membrane barrier separating two aqueous compartment (Forgac, 1988).
Brain Microcirculation
Published in John H. Barker, Gary L. Anderson, Michael D. Menger, Clinically Applied Microcirculation Research, 2019
The barrier to protein is the classical “blood-brain barrier”. This may reside in very tight junctions between endothelial cells. However, opening of these junctions may not be the way or the only way in which protein enters the brain in pathologic conditions. Normally, the endothelium of brain microvessels has only a scant number of vesicles. However, in pathologic states, the number of vesicles may greatly increase and some evidence has been presented that vesicular transport is important.
Human ovarian granulosa cells use clathrin-mediated endocytosis for LDL uptake: immunocytochemical and electron microscopic study
Published in Ultrastructural Pathology, 2023
Aynur Abdulova, Merjem Purelku, Hakan Sahin, Gamze Tanrıverdi
Regarding the clathrin-mediated endocytic pathway, an important component is the clathrin protein. Clathrin-coated vesicles have a three-layered structure consisting of an outer region formed by clathrin proteins in the form of a cage, an intermediate region consisting of a lipid membrane, as well as internal adaptor proteins (APs).8 Along with clathrin, more than 60 other cytosolic proteins are involved in the formation of clathrin-coated endocytic vesicles.9 All these proteins assemble from the cytosol to the endocytic region in a highly ordered manner. The collected vesicles are transported to the target site by SNARE (N-ethylmaleimide-sensitive factor binding protein receptor) proteins. SNAREs manage the transfer of material to be transported during vesicular transport. In an animal cell, there are at least 20 different organelle-associated SNARE proteins, each attached to a specific membrane involved in the biosynthetic-secretion or endocytic pathway. These proteins function as transmembrane proteins and are referred to as vesicular SNAREs (v-SNAREs) with characteristic spiral domains.10
Long-term consumption of alcohol exacerbates neural lesions by destroying the functional integrity of the blood–brain barrier
Published in Drug and Chemical Toxicology, 2022
Jiangping Wei, Lixia Qin, Ying Fu, Yuan Dai, Yueqiang Wen, Shijun Xu
Mfsd2a, also known as sodium-dependent lysophosphatidylcholine symporter-1, is selectively located in the endothelium of blood vessels, maintains the integrity of the BBB and transports nutrients into the brain (Yang et al. 2017). However, few reports have examined the interaction of Mfsd2a and Aβ. In this study, we observed that the expression of Mfsd2a in the brain significantly decreased after mice were treated with alcohol. Although this result did not indicate that Mfsd2a regulated Aβ, it suggested that the capacity for vesicular transport decreased. RAGE and LRP1 are major transporters that transport soluble free Aβ into the brain and from the brain into the blood, respectively (Bell et al. 2007, Deane et al. 2009). In this study, we found that the expressions of LRP1 and RAGE in the brain decreased clearly. This suggested that alcohol consumption caused an impairment in the expressions of LRP1 and RAGE. AQP4 is another important regulator that mediates the elimination of Aβ by regulating the drainage of interstitial fluid (Iliff et al. 2012, Arbel-Ornath et al. 2013, Xu et al. 2015, Burfeind et al. 2017). In this study, we observed a decrease in the expression of AQP4 in brain tissue. These results indicated that long-term consumption of alcohol led to dysfunction of the BBB.
Calcium Signaling Commands Phagosome Maturation Process
Published in International Reviews of Immunology, 2019
Gourango Pradhan, Philip Raj Abraham, Rohini Shrivastava, Sangita Mukhopadhyay
Some intracellular pathogens like Brucellae sp., Chlamydiae sp., Legionellae sp., Salmonella sp., and M. tuberculosis actively evade phagolysosomal pathway. Vacuoles containing these pathogens deviate from the phagolysosomal pathway and fail to attain lysosomal characteristics [109,110]. Though the molecular mechanism of this process is still largely unknown, the host GTPases, Dynamin and other proteins involved in vesicular transport are probably involved. RabGTPase and Golgin84 have been found to be associated with Chlamydia sp.-mediated Golgi fragmentation, which is required for generating the Chlamydia sp. containing vacuoles [111]. Mycobacteria and Salmonella sp. exploit another strategy to avoid terminal phagolysosome formation and block phagosome maturation. Mycobacterial vacuoles contain the early-endosomal marker Rab5 and exclude the late-endosomal GTPase Rab7, indicating an early arrest of the vacuole maturation [110]. Salmonella sp. inhibits the phagosome maturation at the later stages. Salmonella typhimurium increases PI3P levels on the vacuole that allows transient acquisition of EEA1, gradual lumen acidification and acquisition of some lysosomal glycoproteins that resembles the late endosome characteristics [112]. However, Salmonella sp. avoid lysosomal degradation mainly by inhibiting the activation of hydrolytic enzymes [113].