... and the accompanying poster, we focus on RPE-specific adaptations of trafficking pathways. We outline mechanisms underlying the polarised expression of membrane proteins, melanosome biogenesis and movement, and endocytic trafficking, as well as photoreceptor outer segment phagocytosis and degradation. We also briefly...

...Mei Jiang; Antonio E. Paniagua; Stefanie Volland; Hongxing Wang; Adarsh Balaji; David G. Li; Vanda S. Lopes; Barry L. Burgess; David S. Williams ABSTRACT Melanosomes are motile, light-absorbing organelles that are present in pigment cells of the skin and eye. It has been proposed that melanosome...

...Zhao Zhang; Juanjuan Gong; Elena V. Sviderskaya; Aihua Wei; Wei Li ABSTRACT Oculocutaneous albinism (OCA) is a heterogeneous and autosomal recessive hypopigmentation disorder, which is caused by mutations of genes involved in pigment biosynthesis or melanosome biogenesis. We have previously...

... in which are associated with hypopigmentation in mice. These pigmentation defects indicate a key, but as yet unexplored, physiological relevance of this complex in the biogenesis of melanosomes. Here, we show that PIKfyve activity regulates formation of amyloid matrix composed of PMEL protein within...

...Thomas Burgoyne; Marie N. O'Connor; Miguel C. Seabra; Daniel F. Cutler; Clare E. Futter ABSTRACT Analysis of melanosome biogenesis in the retinal pigment epithelium (RPE) is challenging because it occurs predominantly in a short embryonic time window. Here, we show that the zebrafish provides...

... laevis melanophores. In these cells, pigment granules (melanosomes) move along microtubules and microfilaments, toward and away from the cell periphery in response to α-melanocyte stimulating hormone (α-MSH) and melatonin, respectively. In this study we show that melanophores possess a complex network...

... the association of Tyr with other cellular proteins. Western blot analysis revealed that Tyrp1, but not Dct, associates with Tyr in murine melanocytes in vivo, and more specifically, in melanosomes. Two-dimensional SDS-PAGE analysis detected heterodimeric species of Tyr and Tyrp1. Taken together, these data...

...Alistair N. Hume; Dmitry S. Ushakov; Abul K. Tarafder; Michael A. Ferenczi; Miguel C. Seabra Melanosome transport in melanocytes is a model system for the study of cytoskeletal regulation of intracellular transport. Melanophilin (Mlph) is a Rab27a- and myosin Va (MyoVa)-binding protein...

... receptors, yet exclusively localized to late endosomes, lysosomes and melanosomes. To dissect the signals responsible for the intracellular localization of OA1, we generated chimeric proteins consisting of the cytosolic domains of OA1 fused to the lumenal and transmembrane domains of LAMP1; in addition, we...

... , melanosomes in the retinal pigmented epithelium (RPE) are distributed abnormally. In this investigation we detected many proteins in RPE cells that could potentially participate in melanosome transport, but of those tested, only myosin VIIa and Rab27a were found to be required for normal distribution. Two...

... identified other regions within the RabF and RabSF motifs that are required for specific targeting of Rab27a to secretory granules or melanosomes, and Rab5a to endosomes. We observed only partial overlap between targeting-determining regions in the Rab proteins examined, suggesting that Rab recruitment may...

...Glynis Scott; Sonya Leopardi; Stacey Printup; Brian C. Madden Melanosomes are specialized melanin-synthesizing organelles critical for photoprotection in the skin. Melanosome transfer to keratinocytes, which involves whole organelle donation to another cell, is a unique biological process...

... significant sequence homologies with several melanosomal proteins. We have studied its intracellular traffic in both pigmented and non-pigmented cells. We report that a di-leucine-based sorting signal (ExxPLL) present in the cytoplasmic domain of QNR-71 is necessary and sufficient for its proper targeting...

...Xufeng Wu; Kang Rao; M. Blair Bowers; Neal G. Copeland; Nancy A. Jenkins; John A. Hammer ABSTRACT 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...

... homozygotes revealed that the lysosomal membrane proteins Lamp I and Lamp II and the melanosomal membrane protein tyrosinase were mislocalized. In particular, the Lamp proteins were clustered on the cell surface. These findings strengthen the evidence for an alternate pathway via the plasma membrane for cargo...

...Thomas Simmen; Andrea Schmidt; Walter Hunziker; Friedrich Beermann ABSTRACT Tyrosinase is a type I membrane protein found in melanosomes, which are lysosomal-like organelles and specific for pigment cells. A mutation of mouse tyrosinase, platinum (c p ), leads to truncation of tyrosinase’s...

..., the melanosome. Each melanocyte is responsible for delivering melanosomes via its extensive dendritic arbor to numerous keratinocytes, which go on to form the pigmented hair shaft. In this study, we show by light immunofluorescence microscopy and immunoelectron microscopy that the myosin V isoform encoded...