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J Invest Dermatol. 2014 Apr;134(4):1056-1066. doi: 10.1038/jid.2013.432. Epub 2013 Oct 18.

Rab11b mediates melanin transfer between donor melanocytes and acceptor keratinocytes via coupled exo/endocytosis.

Author information

1
CEDOC, Faculdade de Ciências Médicas, Universidade Nova de Lisboa, Lisboa, Portugal; Instituto Gulbenkian de Ciência, Oeiras, Portugal; Molecular Medicine, National Heart and Lung Institute, Imperial College London, London, UK.
2
Molecular Medicine, National Heart and Lung Institute, Imperial College London, London, UK.
3
CEDOC, Faculdade de Ciências Médicas, Universidade Nova de Lisboa, Lisboa, Portugal; Instituto Gulbenkian de Ciência, Oeiras, Portugal.
4
Craniofacial and Orbito-Palpebral Surgery Unit at Chelsea and Westminster Hospital, London, UK.
5
Laboratorio di Fisiopatologia Cutanea, Istituto Dermatologico San Gallicano, IFO, Rome, Italy.
6
Laboratorio di Fisiopatologia Cutanea, Istituto Dermatologico San Gallicano, IFO, Rome, Italy; Dipartimento di Medicina Clinica e Molecolare, Azienda Ospedaliera Sant'Andrea, Università di Roma 'La Sapienza', Rome, Italy.
7
CEDOC, Faculdade de Ciências Médicas, Universidade Nova de Lisboa, Lisboa, Portugal.
8
Institute of Ophthalmology, University College London, London, UK.
9
CEDOC, Faculdade de Ciências Médicas, Universidade Nova de Lisboa, Lisboa, Portugal. Electronic address: duarte.barral@fcm.unl.pt.
10
CEDOC, Faculdade de Ciências Médicas, Universidade Nova de Lisboa, Lisboa, Portugal; Instituto Gulbenkian de Ciência, Oeiras, Portugal; Molecular Medicine, National Heart and Lung Institute, Imperial College London, London, UK. Electronic address: miguel.seabra@fcm.unl.pt.

Abstract

The transfer of melanin from melanocytes to keratinocytes is a crucial process underlying maintenance of skin pigmentation and photoprotection against UV damage. Here, we present evidence supporting coupled exocytosis of the melanin core, or melanocore, by melanocytes and subsequent endocytosis by keratinocytes as a predominant mechanism of melanin transfer. Electron microscopy analysis of human skin samples revealed three lines of evidence supporting this: (1) the presence of melanocores in the extracellular space; (2) within keratinocytes, melanin was surrounded by a single membrane; and (3) this membrane lacked the melanosomal membrane protein tyrosinase-related protein 1 (TYRP1). Moreover, co-culture of melanocytes and keratinocytes suggests that melanin exocytosis is specifically induced by keratinocytes. Furthermore, depletion of Rab11b, but not Rab27a, caused a marked decrease in both keratinocyte-stimulated melanin exocytosis and transfer to keratinocytes. Thus, we propose that the predominant mechanism of melanin transfer is keratinocyte-induced exocytosis, mediated by Rab11b through remodeling of the melanosome membrane, followed by subsequent endocytosis by keratinocytes.

PMID:
24141907
DOI:
10.1038/jid.2013.432
[Indexed for MEDLINE]
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