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Cytotoxicology Studies of 2-D Nanomaterials
Published in Suresh C. Pillai, Yvonne Lang, Toxicity of Nanomaterials, 2019
Priyanka Ganguly, Ailish Breen, Suresh C. Pillai
Clathrin-coated vesicles are utilised to internalise NMs of size usually <100 nm. It is a receptor-mediated endocytosis pathway, where the plasma membrane undergoes inward budding and forms vesicles. The vesicles are layered with various protein receptors permitted to internalise the specific molecule (Sorkin and Puthenveedu, 2013). In this energy-dependent process the clathrin does not interact with the membrane or the ingested particles. It completely depends on the protein receptors and the accessory proteins present on the walls of the vesicles. The accessory proteins are the cytoplasmic proteins which are later subjected to reuse for another endocytosis cycle. The internalised NMs experience organization in the endosomes and are later sent to the surface or delivered to other mature endosomes like lysosomes (McMahon and Boucrot, 2011). The uptake of nutrients, activation of signalling pathways, regulation of surface expression of proteins, and retrieval of proteins deposited after vesicle fusion are some of the functions associated with clathrin-mediated endocytosis (Chen et al., 1998; Liu et al., 2001; McMahon and Boucrot, 2011; Motley et al., 2003; Sikora et al., 2017).
Growth Factor Receptors
Published in Enrique Pimentel, Handbook of Growth Factors, 2017
Receptor-mediated endocytosis has been classified into four categories, based on the final destination of both receptor and ligand.55 In the class I category, receptor and ligand dissociate from one another and the receptor is recycled to the cell surface whereas the ligand is degraded in lysosomes. In the class II category, receptor and ligand both recycle to plasma membrane. In the class III category, both receptor and ligand are transported to lysosomes. Finally, in the class IV category the ligand-receptor complexes are delivered to the opposite sides of polarized cells in a process referred to as transcytosis, the ligand is released intact on the opposite side of the membrane, and the receptor is either degraded or recycled. Despite the heterogeneity of receptors, the initial step of endocytosis for all four classes of cell surface receptors is the same: the ligand-receptor complex is internalized via clathrin-coated pits. When clathrin-coated pits are saturated with receptors, they invaginate, forming a clathrin-coated vesicle. These vesicles lose their clathrin and undergo an acidic shift in pHi resulting in an endosome.
ral Gene Products and Their Regulation
Published in Juan Carlos Lacal, Frank McCormick, The ras Superfamily of GTPases, 2017
Affinity-purified antibodies to recombinant RalA have shown that like Ras, p24 Ral is found almost exclusively in membrane fractions of cell lysates.14 In the marine ray, Discopyge ammala, Ral has been detected in isolated synaptic vesicles and appears to be concentrated in presynaptic terminals.15 Since these antibodies were made against the entire RalA protein, they likely cross-react with the highly similar RalB. Thus, it is not known at present which ral family member is being observed. We used these same antibodies (kindly provided by P. Chardin) in immunofluorescence experiments with NIH 3T3 cells. Figure 1 shows punctate staining throughout the cytoplasm consistent with the presence of p24 Rai in vesicles. The staining pattern was not consistent with vesicles associated with Golgi, the subcellular site of Rap, Arf, and some Rab family members. The pattern was more similar to vesicles of the endocytic pathway such as clathrin-coated vesicles and smooth endosomes.
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
The roles of epidermal growth factor receptor in viral infections
Published in Growth Factors, 2022
Activated EGFR are rapidly internalised and ligand-induced endocytic trafficking is important in regulating duration and intensity of signal transduction. Clathrin-mediated endocytosis (CME) is a major mechanism of EGFR internalisation. Activated receptors are recruited into clathrin-coated pits which are further invaginated and pinched off as clathrin-coated vesicles. Once endocytosed, receptor-containing vesicles are uncoated and fuse with early endosomes. In early endosomes, the internalised receptors are either recycled to the cell surface or taken up into intraluminal vesicles which eventually lead to the delivery of EGFR to lysosome for degradation (Goh et al. 2010). Trafficking of receptors to lysosomal degradation results in signal attenuation, whereas receptors that are recycled can be re-stimulated by ligands that present. The endocytic routes of EGFR are depending on the types of ligands bound (Burke, Schooler, and Wiley 2001). Stimulations of EGF, HB-EGF and BTC lead to lysosomal degradation of EGFRs, whereas stimulations of AR, TGF-α and EPI lead to receptor recycling (Roepstorff et al. 2009).
Clathrin-mediated integrin αIIbβ3 trafficking controls platelet spreading
Published in Platelets, 2018
Wen Gao, Panlai Shi, Xue Chen, Lin Zhang, Junling Liu, Xuemei Fan, Xinping Luo
Another two critical components of clathrin-coated vesicles were also examined. AP2, as a main clathrin adaptor, plays a pivotal role in cargo selection and clathrin coat assembly. After the formation of clathrin-coated vesicles, the mechanochemical enzyme dynamin is recruited to the complex to help clathrin-coated vesicles detached from the neck. In our study, the inhibitors of AP2 and dynamin indeed impaired αIIbβ3 internalization (Figure 4C), confirming that αIIbβ3 traffic is mainly clathrin-mediated and pitstop 2 functioned through a different mechanism from the two inhibitors.