Chapter 6 New Insights into Melanosome Transport in Vertebrate Pigment Cells

Aspengren, Sara; Hedberg, Daniel; Sköld, Helén Nilsson; Wallin, Margareta

doi:10.1016/s1937-6448(08)01606-7

Cited by 109 publications

(115 citation statements)

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“…Cultured melanophores treated with α-melanocyte-stimulating hormone experience a burst of cAMP levels, which in turn activates PKA and leads to the dispersion of melanosomes on the actin network, a process responsible for the darkening the animal's skin color (36)(37)(38). The opposite process occurs during aggregation, when cAMP levels are reduced and melanosomes are transferred from the actin to the microtubule network to be clustered in the cell center (36,38,39). Consistent with these observations, PKA was found to associate with melanosomes and even to form complexes with the respective motor proteins in melanophores (40,41).…”

Section: Significancementioning

confidence: 99%

Myosin Va’s adaptor protein melanophilin enforces track selection on the microtubule and actin networks in vitro

Oberhofer

Spieler

Rosenfeld

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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Pigment organelles, or melanosomes, are transported by kinesin, dynein, and myosin motors. As such, melanosome transport is an excellent model system to study the functional relationship between the microtubule-and actin-based transport systems. In mammalian melanocytes, it is well known that the Rab27a/melanophilin/myosin Va complex mediates actin-based transport in vivo. However, pathways that regulate the overall directionality of melanosomes on the actin/microtubule networks have not yet been delineated. Here, we investigated the role of PKA-dependent phosphorylation on the activity of the actin-based Rab27a/melanophilin/myosin Va transport complex in vitro. We found that melanophilin, specifically its C-terminal actin-binding domain (ABD), is a target of PKA. Notably, in vitro phosphorylation of the ABD closely recapitulated the previously described in vivo phosphorylation pattern. Unexpectedly, we found that phosphorylation of the ABD affected neither the interaction of the complex with actin nor its movement along actin tracks. Surprisingly, the phosphorylation state of melanophilin was instead important for reversible association with microtubules in vitro. Dephosphorylated melanophilin preferred binding to microtubules even in the presence of actin, whereas phosphorylated melanophilin associated with actin. Indeed, when actin and microtubules were present simultaneously, melanophilin's phosphorylation state enforced track selection of the Rab27a/melanophilin/ myosin Va transport complex. Collectively, our results unmasked the regulatory dominance of the melanophilin adaptor protein over its associated motor and offer an unexpected mechanism by which filaments of the cytoskeletal network compete for the moving organelles to accomplish directional transport on the cytoskeleton in vivo.melanophilin | myosin Va | intracellular transport | transport regulation

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Section: Significancementioning

confidence: 99%

Myosin Va’s adaptor protein melanophilin enforces track selection on the microtubule and actin networks in vitro

Oberhofer

Spieler

Rosenfeld

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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“…In both neural and hormonal regulation, the signals that trigger the reactions to generate efferent cues for the effector cells i.e., the chromatophores, either from the external environment or those from internal organs that do not influence the pigment cells directly, are processed in the CNS (Iwata and Fukuda, 1973;Fujii and Oshima, 1986;Baker, 1991;Fujii, 1993 andGulzar et al, 2014). The pigment can be either dispersed throughout the cell, which gives a dark appearance, or it can be aggregated around the nucleus, which gives a pale appearance (Bagnara and Hadley, 1973;Fujii, 2000 andAspengren et al, 2008). Chromatophore cells, a special class of pigment cells in cold blooded animals, have shown great potential in their use as a cell-based biosensor in the detection of a broad range of environmental toxicants (McFadden, 2002;Dierksen et al, 2004;Mojovic et al, 2004;Hutchison et al, 2008;Dukovcic, 2009;Dukovcic et al, 2010a;Dukovcic et al, 2010b andRoach, 2012).…”

Section: Discussionmentioning

confidence: 99%

Effect of cadmium chloride on general body colouration and chromatophores of stinging cat fish, Heteropneustes fossilis (Bloch)

Ahmad¹,

Mishra

Kasherwani

et al. 2018

JANS

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Chromatophores, specialized pigment cells in poikilothermic animals, have shown great potential in their use as a cell-based biosensor in the detection of a broad range of environmental toxicants, as structure and number of chromatophores alters significantly under toxicant exposure. Skin coloration of Heteropneustes fossilis is due to melanin containing melanophores. Cadmium, the black listed and non essential heavy metal, is widely used that adversely affects vital activities of aquatic biota. H. fossilis, freshwater Indian stinging catfish, were subjected to exposure of 96 hour LC 50 dose (392.92 mg/l) and 25% of 96 hour LC 50 dose (98.23mg/l) of cadmium chloride (CdCl 2 ) to evaluate toxic impact of cadmium on colouration and chromatophores. A significant decrease was observed in number of chromatophores after acute (highly significant (F = 70.50; P<0.001) and sub acute (significant (F = 0.29; P<0.05) exposure along with heavy nacrotic, lytic and degenerative changes. Chromatophore gradually changed from reticulate to punctate-stellate and punctuate type as they lost their dendritic processes and aggregation of melanin towards centre. Most of the chromatophores lost their cellular entity due to degenerative changes and melanin was found dispersed in surrounding matrix. Peeling and fading of skin was the common feature in all exposure durations. Fish chromatophores may serve as better biomarkers in reference to metallic pollution and will also be helpful in accessing the health status of economically important fishes as well as worsening status of aquatic bodies.

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“…Recently, studies have been conducted on the often more complex nuptial colour patterns that are used for courtship and aggression. For a more comprehensive overview of fish coloration and patterns, including regulation and mechanisms behind the different types of colour changes, we refer to recent and classic reviews as well as some particularly relevant original publications (Kasukawa et al, 1987;Fujii and Oshima, 1994;Fujii 2000;Amundsen and Forsgren 2001;Nilsson Sköld et al, 2002;Siebeck 2004;Nilsson Sköld et al, 2008;Aspengren et al, 2008;Mills and Patterson 2009;Leclercq et al, 2010). To fully understand short-term regulation of fish coloration one needs to address a wide range of phenomena: from the very fine details of the intracellular motile machineries to the complex chromatic interaction between tissue types and the signalling behaviours of the animals.…”

mentioning

confidence: 99%

“…Methodology for assessing fish coloration and colour change 2.1 Assays for analysis of rapid colour change 2.1.1 Skin biopsies Skin biopsies can be excised from various parts of the fish body depending of purpose and area of interest. We have recently used biopsies from the abdomen (Nilsson Sköld et al, 2008; because these contain both epidermal (external) and peritoneal (internal) chromatophores (Figure 2). Melanophores, erythrophores, xanthophores, leucophores and iridophores are the most common chromatophore types found in the skin of fish.…”

mentioning

confidence: 99%

“…In the Ringer's saline, the chromatphores are more or less dispersed. In order to trigger the pigment aggregation response, the biopsies can then be transferred into Nunc plastic wells (VWR International AB Stockholm) containing either Atlantic cod Ringer´s saline as a control, or freshly diluted 10 M melatonin or norepinephrine (Sigma Aldrich, St. Louis, MO, USA), to induce pigment aggregation (Nilsson Sköld et al, 2008). Norephinephrine appears to be a general pigment aggregating agents across species, but melatonin varies in effectiveness among species.…”

mentioning

confidence: 99%

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