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Melanosome - Wikipedia, the free encyclopedia A melanosome is a cellular organelle containing melanin, the commonest light-absorbing pigment found in the animal kingdom. Melanosomes are bound by a lipid membrane and are generally rounded, sausage-like or cigar-like in shape. Melanosomes are believed to template melanin polymerization by way of amyloidogenesis of the protein pMel, which is present in abundant quantities in melanosomes. en.wikipedia.org /wiki/Melanosome   (344 words)

Albinism and Melanosomal Abnormalities An albino locus-induced diminution of melanosome size suggests that the albino locus is involved in structural features of melanosomes not directly related to the synthesis and deployment of tyrosinase. Ratio data on melanosome length-to-width confirm that the agouti locus determines melanosome shape, either spherical or elliptical; melanization is not required for melanosomes to achieve their agouti-locus-determined shapes. On the ultrastructural level, the hypomelanotic skin and hair of TS were associated with a decrease in the synthesis, melanization, and size of melanosomes; the decrease in the size of melanosomes resulted in the aggregation of melanosomes (i.e., a melanosome complex) in the keratinocytes in all the specimens examined. whitedobes.doberinfo.com /melanosome.html   (6401 words)

Forum Scientium, thesis abstract   (Site not responding. Last check: 2007-11-03) It is nowadays well established that melatonin-stimulation of melanophores results in aggregation of melanosomes to the cell center and that the evident outcome is more transparent cells. Melanosome aggregation was accompanied by tyrosine phosphorylation as shown by immunoblots. The effect of nitric oxide synthase inhibition on melanosome aggregation was not mediated via changes in the tyrosine-phosphorylated protein. www.ifm.liu.se /scientium/publications/theses/annka.html   (360 words)

The melanosome: threshold temperature for explosive vaporization   (Site not responding. Last check: 2007-11-03) The melanosome: threshold temperature for explosive vaporization and internal absorption coefficient during pulsed laser irradiation The explosive vaporization of melanosomes in situ in skin during pulsed laser irradiation (pulse duration less than 1 microsecond) is observed as a visible whitening of the superficial epidermal layer due to stratum corneum disruption. The in vivo absorption spectrum (380-820 nm) for human epidermal melanin was measured by an optical fiber spectrophotometer and is compared with the melanosome spectrum. omlc.ogi.edu /pubs/abs/jacques91a.html   (187 words)

Exploring the Proteome II-Posters Presentations   (Site not responding. Last check: 2007-11-03) The biogenesis of melanosomes is still a hotly debated area of pigment cell research. However, study of early stage melanosomes, which might shed light on their biogenesis, is limited because of the difficulty in obtaining them in sufficiently pure form for analysis. These results indicate that melanosomes represent modified lysosomes with several ER components and only contain a limited number of specific proteins that provide the melanosome with its unique architecture and function. fmp.cit.nih.gov /proteome/posters/poster12.html   (270 words)

Visualization of Melanosome Dynamics within Wild-Type and Dilute Melanocytes Suggests a Paradigm for Myosin V Function ... Rapid, bidirectional melanosome translocation in the periphery of dilute melanocytes. The identification of these organelles as melanosomes is certain because they can also be seen to move in brightfield images, where the fl melanin within them is the only thing visible, and because these fl objects match the match the size and shape of authentic melanosomes. endogenous myosin Va from melanosomes in the periphery. www.jcb.org /cgi/content/full/143/7/1899   (9614 words)

BIOalternatives : Laboratory for the pharmaceutical, cosmetic and molecular test in vitro - Melanosome transfer Melanosome transfer from melanocytes to epidermal keratinocytes is critical for skin pigmentation and inhibition of this process results in skin lightening This assay is suggested for the precise evaluation of potential effectors of particle phagocytosis by keratinocytes (convenient model for detection of potential modulators of melanosome uptake by NHEK). Flow cytometry assay in K/M cocultures, in which melanocytes are labelled by a fluorescent probe and keratinocytes are identified by specific immunolabelling. www.bioalternatives.com /pages/5_4_5.asp   (217 words)

The Actin-Binding Domain of Slac2-a/Melanophilin Is Required for Melanosome Distribution in Melanocytes -- Kuroda et ... on melanosomes and myosin Va (18, 41, 46, 51). Expression of both proteins affected neither the normal distribution of melanosomes at the periphery of the cells, as revealed by bright-field images (D and H), nor localization of Rab27A (B and F) and myosin Va (C and G) on the melanosomes. melanosomes (9.5% ± 3.8% and 14.9% ± 5.7% abnormality, mcb.asm.org /cgi/content/full/23/15/5245   (6292 words)

The Role of Rab27a in the Regulation of Melanosome Distribution within Retinal Pigment Epithelial Cells -- Futter et ... melanosome and myosin Va to actin and melanophilin is a linker Oblique sections (D and E) show that many melanosomes are above the level of the adherens junctions (arrows) and extend into the apical processes between the ROS in the heterozygous (+/–, phenotypically normal) mouse (D), whereas in the homozygous (–/–) ashen mouse (E) the melanosomes remain below the level of the junctions. Melanosomes below the adherens junctions (AJ) are devoid of actin staining (asterisks in B), whereas those above the junctions are closely associated with F-actin staining (arrowheads in B). www.molbiolcell.org /cgi/content/full/15/5/2264   (6370 words)

Rab27a: A Key to Melanosome Transport in Human Melanocytes -- Bahadoran et al. 152 (4): 843 -- The Journal of Cell ... Melanosome distribution is markedly impaired in GS melanocytes. Note that despite the reduction of melanosome number, both partially (white arrowheads) and fully pigmented (fl arrowheads) melanosomes are found in the dendrite of the GS melanocyte. The predominant defect in dilute melanocytes is in melanosome distribution and not cell shape, supporting a role for myosin V in melanosome transport. www.jcb.org /cgi/content/full/152/4/843   (4690 words)

Melanin Pigmentation in Mammalian Skin and Its Hormonal Regulation -- Slominski et al. 84 (4): 1155 -- Physiological ... Electron microscopy of melanosome development during eumelanogenesis in normal melanocytes (a–f), of pheomelanogensis (g–j), and of granular melanosomes in melanoma cells that synthesize eumelanin (k). the transport of TRPs from the TGN to melanosomes (335, 692). the melanosomal membrane) (262, 594, 597, 598), and of GSH in physrev.physiology.org /cgi/content/full/84/4/1155   (6673 words)

Rab27a enables myosin Va-dependent melanosome capture by recruiting the myosin to the organelle. Rab27a enables myosin Va-dependent melanosome capture by recruiting the myosin to the organelle.This phenotype suggests that ashen melanocytes, like dilute melanocytes, are defective in peripheral melanosome capture. Rab27a colocalizes with end-stage melanosomes in wild-type cells, and is most concentrated in melanosome-rich dendritic tips, where it also colocalizes with myosin Va. The peripheral accumulation of melanosomes characteristic of wild-type mouse melanocytes is driven by a cooperative process involving long-range, bidirectional, microtubule-dependent movements coupled to capture and local movement in the actin-rich periphery by myosin Va, the product of the dilute locus. www.ihop-net.org /UniPub/iHOP/gp/8762782.html   (319 words)

Characterization of the Molecular Defects in Rab27a, Caused by RAB27A Missense Mutations Found in Patients with ... Melanosome Immunopurification-- B16 cells grown on 10-cm dishes were washed three times with cold PBS and scraped in a buffer containing 50 m Melanosomes (Tyrp-1; b), Rab27a (e), or melanophilin (Mlph; h) were observed (in red) after labeling with the appropriate antibodies. Melanosomes (Tyrp-1; b), myosin-Va (MVa; e), or melanophilin (Mlph; h) were observed (in red) after labeling with the appropriate antibodies. www.jbc.org /cgi/content/full/278/13/11386   (4553 words)

CAMB: Faculty: Mickey Marks Melanosomes are unique lysosome-related organelles present only in cells that make melanin, the major synthesized pigment in mammals. Melanosomes are among a number of tissue-specific lysosome-related organelles that are disrupted in a group of rare heritable disorders, including Hermansky-Pudlak and Chediak-Higashi syndromes, and pigment cell-specific proteins that localize to melanosomes are targets for the immune system in patients with melanoma. By using biochemical and morphological approaches to follow the fates of melanosome-specific and ubiquitous endosomal and lysosomal proteins within pigment cells, we are beginning to (1) outline protein transport pathways that lead to the formation of these unusual organelles and (2) dissect biochemical pathways that lead to their morphogenesis. www.med.upenn.edu /camb/faculty/cbp/marks.html   (598 words)

Cyclic AMP promotes a peripheral distribution of melanosomes and stimulates melanophilin/Slac2-a and actin association ... In the cell body, melanosomes move on the microtubule network using kinesin as motor for the anterograde transport and dynein for the retrograde transport. At the cell periphery, melanosomes are transported on the actin network by myosin Va, which is linked to melanosome by the complex Rab27a-memlanophilin/Slac2-a. This phenomenon would strengthen the association of melanosome to the actin network, affect the equilibrium between anterograde and retrograde transport, and allow capture of melanosome at the dendrite tips of melanocytes. www.fasebj.org /cgi/content/full/18/9/989   (1448 words)

UPENN || Graduate Studies in Pharmalogical Sciences Graduate Group Melanosomes are tissue-specific lysosome-related organelles that function in the synthesis and storage of melanins. We are trying to understand how the melanosome is formed, how melanosomal proteins are segregated from lysosomal proteins and contribute to the morphogenesis of melanosomes, and how protein segregation may be regulated within pigment cells. Proprotein convertase cleavage liberates a fibrillogenic fragment of a resident glycoprotein to initiate melanosome biogenesis. www.med.upenn.edu /pharmgg/bios/marks.html   (584 words)

Melanosome absorption coefficient of melanosomes in ex vivo human skin specimens, and the literature data for similar in vivo measurements. A Q-switched pulsed ruby laser (40 ns pulse duration) irradiated pigmented skin samples causing the melanosomes to explosively vaporize which caused a temporary whitening of the skin due to microcavity formation. of melanosomes isolated from the bovine retinal pigmented epithelium. omlc.ogi.edu /spectra/melanin/mua.html   (467 words)

Influence of {alpha}-melanocyte-stimulating hormone and ultraviolet radiation on the transfer of melanosomes to ... Purified melanosomes or different sized fluorescent beads were added in excess to keratinocytes and uptake was followed over time. Significant uptake occurred within 18 h as demonstrated by the bright perinuclear fluorescence in the case of beads (A, B) and by the clear intracellular localization of the dark melanosomes at 24 and 48 h, respectively (C, D). Summary of the effects of UV or MSH on melanogenesis and melanosome transfer by melanocytes and keratinocytes. www.fasebj.org /cgi/content/full/16/1/105   (1504 words)

Filopodia are conduits for melanosome transfer to keratinocytes -- Scott et al. 115 (7): 1441 -- Journal of Cell Science Melanosomes have redistributed towards the melanocyte cell body, leaving a dendrite that appears empty. A string of melanosomes (approximately four of them; arrowhead) is present within a projection arising from the side of the body of the melanocyte dendrite. Melanosomes were aligned along the base of filopodia (e) and were present along the length of areas of contact between melanocytes and keratinocyte (KC; f). jcs.biologists.org /cgi/content/full/115/7/1441   (7385 words)

Abstract The melanocortin 1 receptor (MC1R) is a key regulator of human pigmentation and is expressed on the surface of melanocytes and melanoma cells. PEP-1 antibodies were used to label Pmel-17 protein in early melanosomes and tyrosinase related protein-1 (TRP-1) in late melanosomes respectively. These results suggest that MC1R is present close to or within the melanosome as well as at the cell surface, and suggests that part of the function of MC1R may be mediated through its association with the melanosome. www.blackwellpublishing.com /esdr2004/abstract.asp?id=18452   (339 words)

TIMING OF ANATEXIS WITHIN METAPELITES OF THE ADIRONDACK HIGHLANDS AND LOWLANDS, NEW YORK In order to ascertain the age of anatexis samples were collected from both leucosome and melanosome in the Lowlands and the Highlands. Euhedral, igneous zircon grains from both leucosome and melanosome samples were dated by U/Pb SHRIMP techniques at the GSC facility in Ottawa. Zircons from the melanosome fractions are commonly rounded and yield ages in the 1250-1350 Ma range, but ca. gsa.confex.com /gsa/2004NE/finalprogram/abstract_69936.htm   (475 words)

Cultured melanocytes from dilute mutant mice exhibit dendritic morphology and altered melanosome distribution -- ... The periphery of the cytoplasm of dilute melanocytes Four stages of melanosome maturation have been described from electron micrographic studies (8, 9). To transport melanosomes, dilute must interact with melanosomes and be a functional motor. www.pnas.org /cgi/content/full/93/25/14554   (4368 words)

Versatile Role of Rab27 in Membrane Trafficking: Focus on the Rab27 Effector Families -- Fukuda 137 (1): 9 -- Journal ... melanosome transfer from the microtubules to the actin filaments. After microtubule-dependent movement driven by the kinesin motor(s), the melanosome is transferred from microtubules to actin filaments by the tripartite protein complex formed by Rab27A, Slac2-a, and myosin Va (21–24, 43). Slac2-a is first recruited to melanosomes through direct interaction of the SHD with Rab27A on melanosomes, and then myosin Va is recruited to the Rab27A·Slac2-a complex through direct interaction with the middle domain of Slac2-a (MBD). jb.oxfordjournals.org /cgi/content/full/137/1/9   (4575 words)

The Slp Homology Domain of Synaptotagmin-like Proteins 1-4 and Slac2 Functions as a Novel Rab27A Binding Domain -- ... TRP-1, a melanosome-resident protein, was also co-localized with Slp2 and Rab27A (white in E and J, merged images of Slp2, Rab27A, and TRP-1), indicating that Slp2 was present in the melanosome along with Rab27A. In B16-F1 wild-type melanoma cells, Slp2 was distributed in the periphery of cells (A), especially at the dendritic tips (A, inset), whereas in melanosome transport-defective S91/Cloudman cells, Slp2 accumulated in the perinuclear region of the cells. (the perinuclear clustering of melanosomes) was observed in this www.jbc.org /cgi/content/full/277/11/9212   (5568 words)

Rab27A-binding protein Slp2-a is required for peripheral melanosome distribution and elongated cell shape in ... Slp2-a is the most abundantly expressed of the Slp- and Slac2-family proteins in melanocytes and colocalizes with Rab27A on melanosomes. Knockdown of endogenous Slp2-a protein by small-interfering RNAs (siRNAs) markedly reduced the number of melanosomes in the cell periphery of mouse melanocytes ('peripheral dilution'). Mmr1p is a mitochondrial factor for Myo2p-dependent inheritance of mitochondria in the budding yeast www.nature.com /ncb/journal/v6/n12/abs/ncb1197.html   (311 words)

Rab27a: A Key to Melanosome Transport in Human Melanocytes -- Bahadoran et al. 152 (4): 843 -- The Journal of Cell ... Rab27a: A Key to Melanosome Transport in Human Melanocytes -- Bahadoran et al. to investigate the role of Rab27a in melanosome transport. melanosome distribution and a lack of Rab27a expression. www.jcb.org /cgi/content/abstract/152/4/843   (1358 words)

Melanophore Review Reconstitution of melanosome motility along microtubules in vitro demonstrated the presence of two distinct motor activities of opposite polarity. The model that has evolved from these observations is that melanosomes are transported across long distances via microtubules in both types of cells, while actin-based transport is probably utilized to achieve uniform distribution of pigment throughout the cell. Mammalian melanocytes also produce melanosomes but, unlike melanophores, pigment in these cells is transported to the cell periphery for subsequent exocytosis to surrounding epithelial cells. www.proweb.org /~kinesin/Melanophore.html   (507 words)

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