| 1. |
- Aspengren, Sara, 1977, et al.
(författare)
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A role for spectrin in dynactin-dependent melanosome transport in Xenopus laevis melanophores
- 2004
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Ingår i: Pigment Cell Research. - : Wiley. - 0893-5785 .- 1600-0749. ; 17:3, s. 295-301
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Tidskriftsartikel (refereegranskat)abstract
- The bi-directional movement of pigment granules in frog melanophores involves the microtubule-based motors cytoplasmic dynein, which is responsible for aggregation, and kinesin II and myosin V, which are required for dispersion of pigment. It was recently shown that dynactin acts as a link between dynein and kinesin II and melanosomes, but it is not fully understood how this is regulated and if more proteins are involved. Here, we suggest that spectrin, which is known to be associated with Golgi vesicles as well as synaptic vesicles in a number of cells, is of importance for melanosome movements in Xenopus laevis melanophores. Large amounts of spectrin were found on melanosomes isolated from both aggregated and dispersed melanophores. Spectrin and two components of the oligomeric dynactin complex, p150(glued) and Arp1/centractin, co-localized with melanosomes during aggregation and dispersion, and the proteins were found to interact as determined by co-immunoprecipitation. Spectrin has been suggested as an important link between cargoes and motor proteins in other cell types, and our new data indicate that spectrin has a role in the specialized melanosome transport processes in frog melanophores, in addition to a more general vesicle transport.
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| 2. |
- Aspengren, Sara, 1977, et al.
(författare)
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Different strategies for color change
- 2009
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Ingår i: Cellular and Molecular Life Sciences (CMLS). - : Springer Science and Business Media LLC. - 1420-682X .- 1420-9071. ; 66, s. 187-191
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Forskningsöversikt (refereegranskat)
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| 3. |
- Aspengren, Sara, 1977, et al.
(författare)
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Effects of acrylamide, latrunculin, and nocodazole on intracellular transport and cytoskeletal organization in melanophores
- 2006
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Ingår i: Cell Motility and the Cytoskeleton. - : Wiley. - 0886-1544 .- 1097-0169. ; 63:7, s. 423-436
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Tidskriftsartikel (refereegranskat)abstract
- The effects of acrylamide (ACR), nocodazole, and latrunculin were studied on intracellular transport and cytoskeletel morphology in cultured Xenopus laevis melanophores, cells that are specialized for regulated and bidirectional melanosome transport. We used three different methods; light microscopy, fluorescence microscopy, and spectrophotometry. ACR affected the morphology of both microtubules and actin filaments in addition to inhibiting retrograde transport of melanosomes but leaving dispersion unaffected. Using the microtubule-inhibitor nocodazole and the actin filament-inhibitor latrunculin we found that microtubules and actin filaments are highly dependent on each other, and removing either component dramatically changed the organization of the other. Both ACR and latrunculin induced bundling of microtubules, while nocodazole promoted formation of filaments resembling stress fibers organized from the cell center to the periphery. Removal of actin filaments inhibited dispersion of melanosomes, further concentrated the central pigment mass in aggregated cells, and induced aggregation even in the absence of melatonin. Nocodazole, on the other hand, prevented aggregation and caused melanosomes to cluster and slowly disperse. Dispersion of nocodazole-treated cells was induced upon addition of alpha-melanocyte-stimulating hormone (MSH), showing that dispersion can proceed in the absence of microtubules, but the distribution pattern was altered. It is well established that ACR has neurotoxic effects, and based on the results in the present study we suggest that ACR has several cellular targets of which the minus-end microtubule motor dynein and the melatonin receptor might be involved. When combining morphological observations with qualitative and quantitative measurements of intracellular transport, melanophores provide a valuable model system for toxicological studies.
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| 4. |
- Aspengren, Sara, 1977, et al.
(författare)
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Effects of Hydroquinone on Cytoskeletal Organization and Intracellular Transport in Cultured Xenopus laevis Melanophores and Fibroblasts
- 2012
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Ingår i: ISRN Cell Biology. - : Hindawi Limited. - 2356-7872 .- 2090-7389. ; 2012
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Tidskriftsartikel (refereegranskat)abstract
- Hydroquinone is used as a skin-lightening agent, it is also present in different chemical products and cigarette smoke. It is believed to inhibit melanin production in melanocytes by inhibiting the key enzyme tyrosinase. In the present study, we show that hydroquinone had severe effects on microtubules and actin filaments in cultured Xenopus laevis melanophores as studied by immunohistochemistry. It affected the intracellular transport of melanosomes, induced bundling of microtubules and disassembly of actin filaments at 10 and 50μM, and at 100μM proper adhesion to the substrate was lost. Effects occurred at lower concentrations than what previously has been stated to be cytotoxic, and the results show that tyrosinase is not the only cellular target. The cytoskeleton is of utmost importance for the function of all cells and across species. Our data has therefore to be considered in the discussions about the use of hydroquinone for bleaching of skin.
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| 5. |
- Aspengren, Sara, 1977, et al.
(författare)
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Melanophores: a model system for neuronal transport and exocytosis?
- 2007
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Ingår i: Journal of neuroscience research. - : Wiley. - 0360-4012 .- 1097-4547. ; 85:12, s. 2591-600
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Forskningsöversikt (refereegranskat)abstract
- Black pigment cells, melanophores, from lower vertebrates are specialized in bidirectional and coordinated translocation of pigment granules, melanosomes, in the cytoplasm. Melanophores develop from the neuronal crest and are most abundant in the dermal and epidermal layers of the skin, where the intracellular distribution of the pigment significantly influences the color of the animal. The transport of pigment is dependent on an intact cytoskeleton and motor proteins associated with cytoskeletal components. The easily cultured melanophores have proved to be excellent models for organelle transport because the intracellular movements of pigment can be visualized via light microscopy, and the granules move in response to defined chemical signals. The ease of achieving a combination of morphological and functional transport studies is the advantage of the melanophore system, and studies on pigment cells have revealed new components of the transport machinery, including molecular motors, their adapters, and transfer of vesicles to other cells. Many cellular components are transported with a combination of the actin- and microtubule-based transport systems, and, since all eukaryotic organisms rely on functional intracellular transport and an intact cytoskeleton, studies on melanophores are important for many aspects of cell biology, including axonal transport. In this review, we present an overview of the research on the pigment transport system and the potential use of pigment cells as a model system.
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| 6. |
- Aspengren, Sara, 1977, et al.
(författare)
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New Insights into Melanosome Transport in Vertebrate Pigment Cells
- 2008
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Ingår i: INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY, Vol 272 (edited by Kwang W. Jeon). - : Elsevier. - 9780123747471 ; 272, s. 245-302
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Pigment cells of lower vertebrates provide an excellent model to study organelle transport as they specialize in the translocation of pigment granules in response to defined chemical cues. This review will focus on the well-studied melanophore/melanocyte systems in fish, amphibians, and mammals. We will describe the roles of melanin, melanophores, and melanocytes in animals, current views on how the three motor proteins dynein, kinesin, and myosin-V are involved in melanosome transport along microtubules and actin filaments, and how signal transduction pathways regulate the activities of the motors to achieve aggregation and dispersion of melanosomes. We will also describe how melanosomes are transferred to surrounding skin cells in amphibians and mammals. Comparative studies have revealed that the ability of physiological color change is lost during evolution while the importance of morphological color change, mainly via transfer of pigment to surrounding skin cells, increases. In humans, pigment mainly has a role in protection against ultraviolet radiation, but also perhaps in the immune system.
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| 7. |
- Aspengren, Sara, 1977, et al.
(författare)
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Noradrenaline- and melatonin-mediated regulation of pigment aggregation in fish melanophores
- 2003
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Ingår i: Pigment Cell Research. - : Wiley. - 0893-5785. ; 16:1, s. 59-64
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Tidskriftsartikel (refereegranskat)abstract
- The effects of melatonin and noradrenaline (NA) on bi-directional melanosome transport were analysed in primary cultures of melanophores from the Atlantic cod. Both agents mediated rapid melanosome aggregation, and by using receptor antagonists, melatonin was found to bind to a melatonin receptor whereas NA binds to an α2-adrenoceptor. It has previously been stated that melatonin-mediated melanosome aggregation in Xenopus is coupled with tyrosine phosphorylation of a so far unidentified high molecular weight protein and we show that although acting through different receptors and through somewhat different downstream signalling events, tyrosine phosphorylation is of the utmost importance for melanosome aggregation mediated by both NA and melatonin in cod melanophores. Together with cyclic adenosine 3-phosphate-fluctuations, tyrosine phosphorylation functions as a switch signal for melanosome aggregation and dispersion in these cells.
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| 8. |
- Aspengren, Sara, 1977, et al.
(författare)
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Rapport forskarenkät 2015
- 2015
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Resultatet av den användarenkät som gjordes av Universitetsbiblioteket bland Göteborgs universitets disputerade forskare och doktorander 2014.
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| 9. |
- Aspengren, Sara, 1977, et al.
(författare)
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Studies of pigment transfer between Xenopus laevis melanophores and fibroblasts in vitro and in vivo
- 2006
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Ingår i: Pigment Cell Research. - : Wiley. - 0893-5785 .- 1600-0749. ; 19:2, s. 136-145
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Tidskriftsartikel (refereegranskat)abstract
- Frog melanophores rapidly change colour by dispersion or aggregation of melanosomes. A long-term colour change exists where melanosomes are released from melanophores and transferred to surrounding skin cells. No in vitro model for pigment transfer exists for lower vertebrates. Frog melanophores of different morphology exist both in epidermis where keratinocytes are present and in dermis where fibroblasts dominate. We have examined whether release and transfer of melanosomes can be studied in a melanophore-fibroblast co-culture, as no frog keratinocyte cell line exists. Xenopus laevis melanophores are normally cultured in conditioned medium from fibroblasts and fibroblast-derived factors may be important for melanophore morphology. Melanin was exocytosed as membrane-enclosed melanosomes in a process that was upregulated by alpha-melanocyte-stimulating hormone (alpha-MSH), and melanosomes where taken up by fibroblasts. Melanosome membrane-proteins seemed to be of importance, as the cluster-like uptake pattern of pigment granules was distinct from that of latex beads. In vivo results confirmed the ability of dermal fibroblasts to engulf melanosomes. Our results show that cultured frog melanophores can not only be used for studies of rapid colour change, but also as a model system for long-term colour changes and for studies of factors that affect pigmentation.
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| 10. |
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