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Molecular Organization of Entamoeba Histolytica
Published in Roberto R. Kretschmer, Amebiasis: Infection and Disease by Entamoeba histolytica, 2020
Isaura Meza, Haydee K. Torres-Guerrero, Marco A. Meraz
Apparently only one isoform of actin is expressed in trophozoites58 although at least 4 actin genes have been found in the genome.7,8 If the same actin gene is expressed during the cell cycle of E. histolytica is still an unresolved question. The lack of binding to DNAse I is also unexplained as the 5′ end amino acids, described in other actins as involved in the binding, are present in the E. histolytica actin. The regulation of actin polymerization or actin binding proteins is likewise unexplored. In free living amebas such as Acanthamoeba and Dictyostelium, actin binding proteins that nucleate or sever actin filaments have been found.62,63 Meza et al.58 observed that Entamoeba actin polymerization is inhibited at 4°C. This property may explain the rounding and detachment of amebas produced by cooling, but as so far, only actin has been clearly identified in Entamoeba, we need more information about actin-regulating proteins to understand its functioning. In Dictyostelium and other eukaryotic cells, there are besides actin-binding proteins, plasma membrane proteins that bind to actin filaments.64 A coordinated interaction of all these proteins would provide the bases for ameboid movement and plasticity.
Tree pollen allergens
Published in Richard F. Lockey, Dennis K. Ledford, Allergens and Allergen Immunotherapy, 2020
Rosa Codina, Fernando Pineda, Ricardo Palacios
A second group of highly cross-reactive allergens includes the profilins. These are actin-binding proteins, expressed in all eukaryotic cells, which link signal transduction processes with the reassembling of the cytoskeleton [39,66]. They are structurally conserved low molecular weight proteins (12–15 kDa) and represent probably the most widely distributed allergens described to date [39]. They include proteins from pollen of botanically unrelated plants (trees, grasses, weeds), for instance, birch pollen (Bet v 2) and olive pollen profilin (Ole e 2), as well as proteins from plant-derived foods (see Table 10.1 and Figure 10.5b).
Cytoskeletons (F-actin) and spermatogenesis
Published in C. Yan Cheng, Spermatogenesis, 2018
Liza O’Donnell, Peter G. Stanton
Various actin-binding proteins are found at the basal ES, with functions including actin bundling and cross-linking (espin, ezrin, fascin 1, palladin, plastin family), branched actin polymerization (Arp2/3 complex, N-WASP), end-capping (Eps8), and branch stabilization (cortactin).68,69 Selective RNAi-mediated knockdown of individual actin-binding protein expression tends to disturb Sertoli cell junction function in vitro as well as F-actin and associated junction protein organization (e.g., targeting fascin 170). However, under these circumstances ES function is not completely ablated, suggesting that multiple proteins contribute to actin dynamics at the basal ES. In contrast, targeted disruption of the branched actin polymerization pathway by knockout of N-Wasp (which acts upstream of Arp2/3) in mouse Sertoli cells caused spermatogenic arrest, loss of expression of connexin-43 and occludin (markers for gap and tight junctions, respectively), and loss of BTB function.71 These studies clearly show control of branched actin polymerization to be an essential component of the maintenance of seminiferous epithelial structure and function.
Dual role of E-cadherin in cancer cells
Published in Tissue Barriers, 2022
Svetlana N. Rubtsova, Irina Y. Zhitnyak, Natalya A. Gloushankova
Establishment and maintenance of linear AJs require both myosin IIA and IIB isoforms. The morphology of linear AJs, compaction of epithelial cells and integrity of epithelial layers depend on acto-myosin contractility.21 Depletion of myosin IIA leads to disruption of linear AJs in the apical part of epithelial cells. Depletion of myosin IIB leads to decrease in actin content in circumferential actin bundles associated with linear AJs.22,23 An adaptor protein afadin is also essential for the proper organization of actin bundles at AJs. Using afadin-KO cells stably expressing afadin mutants with various deleted regions, it was shown that afadin binds to α-catenin through its coiled-coil (CC) region.24 Another actin-binding protein, EPLIN, additionally stabilizes the circumferential actin bundle by inhibiting actin depolymerization and crosslinking actin filaments.25 Several studies have demonstrated that siRNA-mediated depletion of EPLIN resulted in disappearance of circumferential actin bundles and converted linear AJs into punctate AJs associated with radial actin bundles.26
Loss of mDia1 and Fhod1 impacts platelet formation but not platelet function
Published in Platelets, 2021
Malou Zuidscherwoude, Elizabeth J. Haining, Victoria A. Simms, Stephanie Watson, Beata Grygielska, Alex T. Hardy, Andrea Bacon, Stephen P. Watson, Steven G. Thomas
Formins are a class of actin-binding proteins known as nucleation-promoting factors, although they have been shown to have functions beyond simple nucleation. Members of the formin protein family have the ability to both nucleate and accelerate the elongation of linear actin fibers and are also involved in microtubule dynamics and organization [12]. Formins are increasingly recognized as regulators of cross-talk between the actin and microtubule cytoskeletons and they can therefore be expected to play a role in multiple aspects of platelet formation and function [13]. Indeed, a gain of function variant of formin mDia1 (DIAPH1) is linked to macrothrombocytopenia in humans [14,15]. Of the 15 mammalian formins, only 4 are expressed in platelets and megakaryocytes, namely mDia1, Fhod1, Daam1, and Inf2 which contribute 24.5%, 36.7%, 14.5%, and 24.3%, respectively, of the total formin protein expressed in mouse platelets [13,16]. We have previously shown that platelets from an mDia1 knockout mouse were functionally normal and hypothesize that this was due to redundant function with other platelet/megakaryocyte expressed formin family members [16]. In support of this, we have recently reported that blocking formin FH2 domains using a small molecule inhibitor (SMIFH2) completely abolishes platelet spreading and disrupts microtubule dynamics [17], highlighting the role of formins in regulating both actin and microtubule platelet cytoskeletons.
The therapeutic effects of blocking IGF-R1 on mice model of skin cancer
Published in Journal of Dermatological Treatment, 2021
Matrix metalloproteases (MMP) plays a crucial role in tumor proliferation, invasion and metastasis. It is has the ability to hydrolyze the major compound in the basement membrane, type IV collagen (23). Moreover, it destructed the basement membranes in blood vessels as well as is engaged in angiogenesis and neovascularization (24). MMP9 helps in the proteolytic conversion of syndecan-1 to be a soluble molecule instead of membrane bound enhancing tumor metastasis. Syndecan-1 possesses the ability to interact with extracellular matrix growth factors such as fibroblast growth factor (FGF) family leading to antigenic stimulation (25). In addition, fascin-1, actin-binding protein, is highly expressed in many cancers such as skin, lung, breast, colon cancers and leukemia. It established the formation of invadopodia in cancer cells (26). Upregulation of fascin causes modifications in the cytoskeleton altering extracellular matrix and enhances tumor metastasis. However, blocking or knocking down of fascin-1 blocked the migration and invasion ability of cancer cells in some cancer types such as hepatocellular carcinoma (27). In skin cancer, fascin is reported to be over expressed leading to locally infiltrate and substitutes the surrounding tissues affecting cell–cell and cell–matrix interaction, enhancing cell adhesion, motility and invasiveness increasing the risk of metastasis (28). However, we found significant increase in the gene and protein expression of MMP9, syndecan-1 and fascin-1 in skin cancer, which are attenuated by treating cancer mice with PQ401 without affecting the control mice.