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Homeostasis of Dopamine
Published in Nira Ben-Jonathan, Dopamine, 2020
The biogenesis, targeting, docking, and fusion of secretory vesicles in chromaffin cells have a similar general pattern to that of the exocytotic machinery of neurons but differ in the following respects. First, secretory granules originate from the trans-Golgi network, where they are loaded with catecholamines, peptide hormones, and chromogranins, with the latter serving as the driving force in their biogenesis [74]. Second, newly formed secretory granules are transported along microtubules to the F-actin-rich cell cortex, where they undergo a maturation process. A Ca2+-induced F-actin rearrangement allows the formation of channel-like structures that are perpendicular to the plasma membrane and serve as conduits for directing the granules to the exocytotic sites. Third, chromaffin cells lack morphologically distinct sites for vesicle fusion such as the active zones in presynaptic neurons and, instead, have hot-spots for Ca2+ entry. Fourth, acetylcholine, released from the splanchnic nerve, is the main physiological stimulus for exocytosis in adrenal chromaffin cells. Following its binding to cholinergic receptors, acetylcholine depolarizes the cells and elicits action potentials that stimulate Ca2+ influx via voltage-dependent Ca2+ channels, thereby triggering exocytosis of the secretory granules. Finally, chromaffin granules are functionally heterogeneous and constitute two discrete pools: a large slowly releasable pool, and a smaller, fully mature, readily releasable pool.
Cell Structure and Functions
Published in Malgorzata Lekka, Cellular Analysis by Atomic Force Microscopy, 2017
All three cytoskeletal components have distinct subcellular localizations. Actin filaments are usually present in a layer known as the “cell cortex,” immediately beneath the plasma membrane, and in cell projections such as microvilli. They are also associated with a number of proteins and other structures, such as the contractile ring in dividing cells or focal contacts linking cytoskeleton with surface receptors. Microtubules extend from the nucleus region towards the cell periphery. Intermediate filaments are distributed in a similar pattern to microtubules. IFs and MTs are excluded from the actively expanding leading edge of the moving or “ruffling” cell [1].
Molecular Structure and Functions of Collagen
Published in Marcel E. Nimni, Collagen, 1988
Marcel E. Nimni, Robert D. Harkness
The role of the extracellular matrix in determining cell shape, orientation, movement, and metabolic activity has generated considerable interest.123 Corneal fibroblasts, which have the capacity to migrate through extracellular matrices, can provide a good model to understand this phenomenon.285 The migrating corneal fibroblast is an elongate, bipolar cell, possessing a leading pseudopodium and a trailing cell process that, by successive attachments and retractions, seems able to change shape and location. Using antibodies to various fibrillar proteins, it was observed that fibroblasts grown in collagen gels exhibit significant ultrastructural differences from those attached to glass surfaces.124 Even dedifferentiated chondrocytes grown on plastic exhibit a network of well-defined fibers, “stress fibers” that stain for actin, α-actinin, and mysosin (Figure 14). These fibers seem to traverse the cell in all directions radiating from the cell surface along lines of stress. In contrast, the cells grown in collagen gels fail to show such patterns, but, rather, show diffuse cytoplasmic staining, and actin and α-actinin but not mysosin, and seem to concentrate in the cell cortex and filipodia.
Anti-integrin therapy for retinovascular diseases
Published in Expert Opinion on Investigational Drugs, 2020
Ashay D. Bhatwadekar, Viral Kansara, Qianyi Luo, Thomas Ciulla
Since their discovery in the 1980s, integrins have been shown to play a key role in multiple diseases, including cancer, diabetic eye diseases, and age-related macular degeneration (AMD). Named for their function as ‘integrators’ of cell surface and extracellular matrix (ECM), integrins are a family of multi-functional cell-adhesion molecules that connect ECM molecules to actin in the cell cortex. Composed of alpha and beta subunits and serving as cell adhesion and cell signaling receptors, they regulate the shape, orientation, and movement of cells. Integrins also regulate a variety of cellular interactions with their microenvironment, such as adhesion, spreading migration, proliferation, invasion, survival, and apoptosis [1]. Consequently, integrins play a role in pathologic processes, such as inflammation, angiogenesis and fibrosis. This report reviews the role of integrins in vitreoretinal diseases and investigational retinal treatments targeting integrins.
Characterization of cell-cell junction changes associated with the formation of a strong endothelial barrier
Published in Tissue Barriers, 2018
MaryPeace McRae, Lindsay M. LaFratta, Benjamin M. Nguyen, Jason J. Paris, Kurt F. Hauser, Daniel E. Conway
In our studies, we observed that HUVEC cells cultured in medium supplemented with cAMP analogues resulted in a tighter barrier, as measured by an increased cellular TEER. On a similar timescale, these cells also displayed increases in ZO-1 and VE-cadherin expression, vinculin recruitment to cell-cell junctions, and decreased cell-cell junctional force. Furthermore, we observed that endothelial cells cultured with cAMP supplementation exhibited more cortical actin, whereas control cells had more stress fiber actin distribution. These data are consistent with stronger adhesion junctions in the cAMP supplemented groups. Others have demonstrated that actin tethering to adhesion complexes is necessary for the formation and stabilization of intercellular junctions.33 Conversely, agents known to disrupt actin tethering (like thrombin and histamine) can result in actin reorganization from the cell cortex into stress fibers that stretch across the cell body. The stress fibers produce a tensile force to pull proteins away from the cell surface inward toward the center of the cell, creating a compromised barrier.33 Our data is consistent with these findings. In these studies, cells were treated with SMIFH2, an inhibitor of formin. Formins act to promote the assembly of linear actin filaments and promote stress fiber formation.34,35 Inhibition of stress fiber formation by SMIFH2 resulted in an increased TEER, consistent with enhanced barrier function.
Identification of the protective effect of Polygonatum sibiricum polysaccharide on d -galactose-induced brain ageing in mice by the systematic characterization of a circular RNA-associated ceRNA network
Published in Pharmaceutical Biology, 2021
Zheyu Zhang, Bo Yang, Jianhua Huang, Wenqun Li, Pengji Yi, Min Yi, Weijun Peng
GO analysis of 679 PSP-related mRNAs identified several GO terms that were highly enriched (Figure 2(E)). The most enriched terms with regards to biological processes were positive regulation of dendritic spine development, cellular component organization, and localization. As for cellular components, the most enriched terms were the intracellular part, organelle part, and cell cortex. The most enriched molecular function terms were protein binding, binding, and protein domain–specific binding. As shown in Figure 2(E), KEGG analysis demonstrated that O-glycan biosynthesis, sulphur metabolism, and adherens junctions, may be closely associated with the ameliorative effect of PSP on cognitive impairment and brain ageing.