Browsing by Subject "Endocytosis"

Now showing 1 - 6 of 6
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    Effect of cholesterol and its autooxidation derivatives on endocytosis and dipeptidyl peptidases of aortic endothelial cells
    (Murcia : F. Hernández, 1992) Fornas, E.; Mayordomo, F.; Renau-Piqueras, J.; Alborch, E.
    The effects of cholesterol (CHO) and cholesterol autooxidation derivatives (CAD) on the endocytosis of cationized ferritin (CF) by endothelial cells have been investigated. The effect of both substances on the activity of lysosomal enzymes dipeptidyl peptidase 1 (DPP 1) and dipeptidyl peptidase 11 (DPP 11) was also studied. Treatment of rats with CAD induced striking alterations in the ultrastructure of endothelial cells and makes it impossible to analyze the effect of this toxin on endocytosis processes. In contrast, CHO-treated cells displayed a good ultrastructural preservation and showed an increased ability to endocyte ferritin, as compared with controls. Both DPPI and DPP 11 activities increased after 3 weeks of CAD or CHO treatment. Our results indicate that although CHO damage endothelial cells, the most important effects could be attributed to CAD which usually accompanies CHO-supplemented diets.
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    Lipid kinases play crucial and multiple roles in membrane trafficking and signaling
    (Murcia : F. Hernández, 2003) Heath, C.M.; Stahl, P.D.; Barbieri, M.A.
    Phosphotidylinositols (PIs) are known to play an essential role in membrane trafficking and signaling transduction. PIs serve multiple functions, such as recruitment of cytosolic proteins with PI phosphate (PIP) binding domains and modification of the physical properties of the membranes in which they reside. As substrates for phosphoinositide-specific lipases they function as a switch point in phosphoinositide metabolism. Recent work with epidermal growth factor receptor (EGFR) and colony stimulating factor-1 receptor (CSFR) has identified a possible connection between endocytosis of activated receptors and type-1 phosphatidylinositol-4-phosphate-5-kinase. Furthermore, serine/tyrosine phosphorylation of phosphatidylinositol- 4-phosphate-5-kinase seems to be essential for its activities. Indeed, one of the products of the phosphatidylinositol-4-phosphate-5-kinases, PIP2, has been shown to be involved in multiple steps of endocytosis, including the assembly of the clathrin coat, regulation of adaptor proteins, and production of endocytic vesicles via the regulation of dynamin. The discussion in this review focuses primarily on receptors with intrinsic enzymatic activity, specifically on receptor tyrosine kinases (RTKs). We will discuss their structure; mechanism of action and potential role in membrane trafficking and/or signaling through the regulation of phosphatidylinositol phosphate kinases.
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    Primary cilia in fibroblast-like type B synoviocytes lie within a cilium pit, a site of endocytosis
    (Murcia : F. Hernández, 2010) Rattner, Jerome B.; Sciore, Paul; Ou, Young; van der Hoorn, Frans A.; Lo, I.K.Y.
    The synovium is a thin connective tissue that lines the joint space of free moving articulations. In this report, the expression, structure, and composition of non-motile (primary) cilia in fibroblast-like synoviocytes (FLS) that populate the synovium have been studied. Primary cilia are non-motile, microtubule-based organelles that have been found in a variety of vertebrate cell types. We document that primary cilia are expressed in normal human synovium FLS, cultured human FLS, and FLS cells present in human synovial fluid, and that the cellular region occupied by the primary cilium shows a similar and highly defined architecture within these FLS. This architecture includes the presence of a unique structure that surrounds the lower portion of the cilium shaft. This structure, given the term cilium-pit, includes a space, the pit reservoir. Actin filament bundles surround the cilium-pit, and when these bundles are removed experimentally the volume of the cilium-pit and its continuity with the extracellular environment changes. Finally, this study documents that the cilium-pit is a site of endocytosis and is also the site for the localization of receptors (TNF receptors TNFR1 and TNFR2) associated with synoviocyte function. Taken together, the results of the present study suggest that the FLS cilium-pit functions to regulate the exposure of the primary cilium, both spatially and temporally to extracellular molecules and to couple primary cilium based signaling pathways with those linked to endocytosis.
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    Rab family small GTPases-mediated regulation of intracellular logistics in neural development
    (Universidad de Murcia. Departamento de Biología Celular e Histología, 2018) Shikanai, Mima; Yuzaki, Michisuke; Kawauchi, Takeshi
    Rab family small GTPases play essential roles in various cellular events via the regulation of intracellular logistics comprising a large number of membrane traffic pathways. Emerging evidence reveals the physiological roles of Rab proteins in several tissues, including developing brains. Many Rab proteins, such as Rab5, Rab6, Rab7, Rab8, Rab10, Rab11, Rab17 and Rab18, are shown to regulate neurite outgrowth in PC12 cells and/or axon and dendrite formation in primary cultured neurons. Recent studies have also revealed in vivo roles of several Rab family small GTPases in brain development and its related neurological disorders. In this review, we introduce the physiological function of Rab family proteins in neural development with particular focus on neurite outgrowth and neuronal migration.
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    Scratching the surface: Actin’ and other roles for the C-terminal Eps15 homology domain protein, EHD2
    (F. Hernández y Juan F. Madrid. Universidad de Murcia. Departamento de Biología Celular e Histología, 2014) Simone, Laura C.; Naslavsky, Naava; Caplan, Steve
    The C-terminal Eps15 homology domaincontaining (EHD) proteins participate in multiple aspects of endocytic membrane trafficking. Of the four mammalian EHD proteins, EHD2 appears to be the most disparate, both in terms of sequence homology, and in subcellular localization/function. Since its initial description as a plasma membrane-associated protein, the precise function of EHD2 has remained enigmatic. Various reports have suggested roles for EHD2 at the plasma membrane, within the endocytic transport system, and even in the nucleus. For example, EHD2 facilitates membrane fusion/repair in muscle cells. Recently the focus has shifted to the role of EHD2 in regulating caveolae. Indeed, EHD2 is highly expressed in tissues rich in caveolae, including fat, muscle and blood vessels. This review highlights cumulative evidence linking EHD2 to actin-rich structures at the plasma membrane, where the plasma membraneassociated phospholipid phosphatidylinositol 4,5- bisphosphate controls EHD2 recruitment. Herein we examine the key pathways where EHD2 might function, and address its potential involvement in these processes.
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    The early endosome, a busy sorting station for proteins at the crossroads
    (Murcia : F. Hernández, 2010) Jovic, Marko; Sharma, Mahak; Rahajeng, Juliati; Caplan, Steve
    Endocytosis marks the entry of internalized receptors into the complex network of endocytic trafficking pathways. Endocytic vesicles are rapidly targeted to a distinct membrane-bound endocytic organelle referred to as the early endosome. Despite the existence of numerous internalization routes, early endosomes (EE) serve as a focal point of the endocytic pathway. Sorting events initiated at this compartment determine the subsequent fate of internalized proteins and lipids, destining them either for recycling to the plasma membrane, degradation in lysosomes or delivery to the trans-Golgi network. Sorting of endocytic cargo to the latter compartments is accomplished through the formation of distinct microdomains within early endosomes, through the coordinate recruitment and assembly of the sorting machinery. An elaborate network of interactions between endocytic regulatory proteins ensures synchronized sorting of cargo to microdomains followed by morphological changes at the early endosomal membranes. Consequently, the cargo targeted either for recycling back to the plasma membrane, or for retrograde transport to the trans-Golgi network, localizes to newly-formed tubular membranes. With a high ratio of membrane surface to lumenal volume, these tubules effectively concentrate the recycling cargo, ensuring efficient transport out of the EE. Conversely, receptors sorted for degradation cluster at the flat clathrin lattices involved in invaginations of the limiting membrane, associating with newly formed intralumenal vesicles. In this review we will discuss the characteristics of early endosomes, their role in the regulation of endocytic transport, and their aberrant function in a variety of diseases.