Browsing by Subject "Golgi complex"

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    A mutation in protein phosphatase type 2A as a cause of melanoma progression
    (Murcia : F. Hernández, 2003) Ito, A.; Koma, Y.; Watabe, K.
    The BL6 subline was derived from the F10 line, which was derived from the B16 mouse melanoma cell line. BL6 cells are more invasive than F10 cells and differ genetically from F10 cells by an alteration of the gene encoding the B56? regulatory subunit of protein phosphatase 2A (PP2A). This alteration results in the transcription of mRNA encoding a truncated variant of the B56?1 isoform (??1). ??1 is capable of targeting PP2A to the specific subcellular sites but incapable of promoting the dephosphorylation of specific substrates that is normally mediated by the B56? subunitcontaining PP2A holoenzyme. It thus appears that activities of this type of holoenzymes decrease in cells expressing ??1. Recently, we found two possible ways how ??1 contributes to the enhanced metastatic potential of BL6 cells. The two ways seemed far away from each other: ??1 influenced both the nuclear and cytoplasmic functions of the cell. In the cytoplasm, ??1 localized at the Golgi complex and accelerated Golgi-mediated vesicle transport. On the other hand, ??1 disturbed the cell-cycle regulation. In response to g-irradiation, protein levels of ??1 were markedly increased in BL6 cells. Subsequently the integrity of cell-cycle checkpoint became more aberrant in BL6 cells than that in F10 cells. These two actions of ??1 could results in the enhancement of the malignant phenotypes of melanoma cells, as discussed in this review.
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    Fragmentation of the Golgi complex of dopaminergic neurons in human substantia nigra: New cytopathological findings in Parkinson's disease
    (Universidad de Murcia. Departamento de Biología Celular e Histología, 2021) Tomás, Mónica; Martínez Alonso, Emma; Martínez Martínez, Narcisa; Cara Esteban, Mireia; Martínez Menárguez, José A.
    Fragmentation of the Golgi ribbon is a common feature of Parkinson’s disease and other neurodegenerative diseases. This alteration could be the consequence of the anterograde and retrograde transport imbalance, α-synuclein aggregates, and/or cytoskeleton alterations. Most information on this process has been obtained from cellular and animal experimental models, and as such, there is little information available on human tissue. If the information on human tissue was available, it may help to understand the cytopathological mechanisms of this disease. In the present study, we analyzed the morphological characteristics of the Golgi complex of dopaminergic neurons in human samples of substantia nigra of control and Parkinson’s disease patients. We measured the expression levels of putative molecules involved in Golgi fragmentation, including αsynuclein, tubulin, and Golgi-associated regulatory and structural proteins. We show that, as a consequence of the disease, the Golgi complex is fragmented into small stacks without vesiculation. We found that only a limited number of regulatory proteins are altered. Rab1, a small GTPase regulating endoplasmic reticulum-to-Golgi transport, is the most dramatically affected, being highly overexpressed in the surviving neurons. We found that the SNARE protein syntaxin 5 forms extracellular aggregates resembling the amyloid plaques characteristic of Alzheimer’s disease. These findings may help to understand the cytopathology of Parkinson’s disease.
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    Structure and Dynamics of the Golgi Complex at 15ºC: Low Temperature Induces the Formation of Golgi-Derived Tubules
    (Wiley, 2005-01) Martínez-Alonso, Emma; Egea, Gustavo; Ballesta Germán, José; Martínez-Menárguez, José Ángel; Biología Celular e Histología
    Immunofluorescence and cryoimmunoelectron microscopy were used to examine the morphological and functional effects on the Golgi complex when protein transport is blocked at the ERGIC (ER-Golgi intermediate compartment) in HeLa cells incubated at low temperature (15ºC). At this temperature, the Golgi complex showed long tubules containing resident glycosylation enzymes but not matrix proteins. These Golgi-derived tubules also lacked anterograde (VSV-G) or retrograde (Shiga toxin) cargo. The formation of tubules was dependent on both energy and intact microtubule and actin cytoskeletons. Conversely, brefeldin A or cycloheximide treatments did not modify the appearance. When examined at the electron microscope, Golgi stacks were long and curved and appeared connected to tubules immunoreactive to galactosyltransferase antibodies but devoid of Golgi matrix proteins. Strikingly, COPI proteins moved from membranes to the cytosol at 15ºC which could explain the formation of tubules.