Membrane Traffic in Disease

Our long term goal is to uncover regulatory mechanisms of membrane trafficking and their role in human disease. 

For this, we use state-of-the-art techniques, such as live-cell imaging and super-resolution confocal microscopy and a broad range of molecular biology, biochemistry and cell biology methods to advance the knowledge in this area.

We focus on the study of small GTPases of the Rab and Arf families of the Ras superfamily, as these are known to be master regulators of all steps of intracellular trafficking. Mutations in several proteins of these families lead to diseases affecting mainly neurons, cilia and lysosome-related organelles, like melanosomes. Moreover, several of these proteins have been implicated in cancer progression.

Thus, the study of the mechanisms of diseases caused by mutations in Rab and Arf proteins, can shed light on the etiology of these diseases and allow a better understanding of the implicated protein functions and also shed light on new therapeutic strategies.



  • Project PRIME (Molecular Mechanisms of Melanin Internalization and Processing by Keratinocytes)
    01/10/2018 – 31/03/2022
    Fundação para a Ciência e a Tecnologia

The skin is the largest organ of the human body and provides protection against external aggressions. The outmost layer, the epidermis is composed mainly by two cell types: melanocytes and keratinocytes. Melanocytes synthesize the pigment melanin and localize to the basal layer. Keratinocytes are present in all the layers and are the final recipients of melanin. Melanin protects skin cells against ultraviolet (UV) radiation-induced damage, which can lead to the onset of skin cancer. Melanin synthesis occurs in specialized organelles called melanosomes, which share several features with lysosomes like low pH, the presence of lysosomal membrane proteins and catalytic enzymes and are thus considered lysosome-related organelles. Once fully mature and located at the tips of melanocyte dendrites, melanosomes are transferred to keratinocytes. We found evidence that the predominant model of melanin transfer is coupled exo/endocytosis, where the melanin core is exocytosed by melanocytes in a process dependent on the small GTPase Rab11b and the exocyst tethering complex, and then internalized by keratinocytes. Despite the crucial role of melanin uptake and processing by keratinocytes for skin pigmentation, the pathways involved have not been characterized. Moreover, after melanin is internalized by keratinocytes, little is known about how it accumulates at the supra-nuclear region of keratinocytes to shield the DNA from UV radiation. Therefore, we propose to study how melanin is internalized and processed by keratinocytes.


    1. Investigate the internalization route followed by melanin in keratinocytes.
    2. Characterize the processing of melanin by keratinocytes.
    3. Determine the mechanism of melanin granule polarization within keratinocytes.

Our initial characterization suggests that melanin is stored in specialized endocytic compartments within keratinocytes that are not highly acidic or degradative, allowing it to resist degradation for long periods and remain during the process of differentiation towards the superficial layers of the stratified epithelium. This study has the potential to provide entirely new concepts in the field of skin pigmentation. Pigmentation disorders cause a reduction in the quality of life of those affected due to their social impact. Also, with the modern lifestyle, photoprotection has become an important issue. Thus, this work can also lead to the identification of novel key regulators that will become drug targets for the pharma, biotech and cosmetic industries.

H. Moreiras, M.C. Seabra, D.C. Barral. “Melanin Transfer in the Epidermis: The Pursuit of Skin Pigmentation Control Mechanisms”. Int J Mol Sci. 2021 Apr 24;22(9):4466. doi: 10.3390/ijms22094466.

H. Moreiras, F.J.C. Pereira, M.V. Neto, L. Bento-Lopes, T.C. Festas, M.C. Seabra, D.C. Barral. "The exocyst is required for melanin exocytosis from melanocytes and transfer to keratinocytes". Pigment Cell Melanoma Res. 2020 Mar;33(2):366-371. doi: 10.1111/pcmr.12840

H. Moreiras, M. Lopes-da-Silva, M.C. Seabra, D.C. Barral. "Melanin processing by keratinocytes: A non-microbial type of host-pathogen interaction?". Traffic. 2019 Apr;20(4):301-304. doi: 10.1111/tra.12638.

Duarte Barral, Principal investigator
Miguel Seabra, co-Principal investigator
Abel Oliva, Investigator
João Pedro Vasconcelos, Investigator
Michael Hall, post-doctoral researcher
Liliana Bento-Lopes, PhD student

  • LYSOCIL: Excel in Rare Diseases Research: Focus on LYSOsomal Disorders and CILiopathies
    11/01/2018 - 30/04/2022
    Horizonte 2020 da União Europeia
    LYSOCIL is a Twinning Project led by NMS|FCM that aims to strengthen the R&I capacity research in rare diseases (RDs), helping it to become a national and internationally-recognized centre of excellence in chronic RDs R&I. CEDOC-NMS|FCM partnered up with two internationally-leading institutions, Münster University (WWU), a German institution with a strong research profile in basic, clinical and translational medicine connected to RDs, and the Telethon Institute of Genetics and Medicine (TIGEM), the leading Italian research center dedicated to understanding the molecular mechanisms behind RDs. This partnership will boost the multidisciplinary knowledge and experience and widen the collaborative networks to step up the excellence of the research of the involved partners.

  • Moreiras H, Bento-Lopes L, Neto MV, Escrevente C, Cabaço LC, Hall MJ, Ramalho JS, Seabra MC, Barral DC. Melanocore uptake by keratinocytes occurs through phagocytosis and involves protease-activated receptor-2 internalization. Traffic. 2022 Jun;23(6):331-345. doi: 10.1111/tra.12843. Epub 2022 May 15. PMID: 35426185.
  • Brito C, Costa-Silva B, Barral DC, Pojo M. Unraveling the Relevance of ARL GTPases in Cutaneous Melanoma Prognosis through Integrated Bioinformatics Analysis. Int J Mol Sci. 2021 Aug 26;22(17):9260. doi: 10.3390/ijms22179260.
  • Silva G, Sales-Dias J, Casal D, Alves S, Domenici G, Barreto C, Matos C, Lemos AR, Matias AT, Kucheryava K, Ferreira A, Moita MR, Braga S, Brito C, Cabral MG, Casalou C, Barral DC, Sousa PMF, Videira PA, Bandeiras TM, Barbas A. Development of Dl1.72, a Novel Anti-DLL1 Antibody with Anti-Tumor Efficacy against Estrogen Receptor-Positive Breast Cancer. Cancers (Basel). 2021 Aug 13;13(16):4074. doi: 10.3390/cancers13164074. 
  • Escrevente C, Bento-Lopes L, Ramalho JS, Barral DC. Rab11 is required for lysosome exocytosis through the interaction with Rab3a, Sec15 and GRAB. J Cell Sci. 2021 Jun 1;134(11):jcs246694. doi: 10.1242/jcs.246694.
  • Moreiras H, Seabra MC, Barral DC. Melanin Transfer in the Epidermis: The Pursuit of Skin Pigmentation Control Mechanisms. Int J Mol Sci. 2021 Apr 24;22(9):4466. doi: 10.3390/ijms22094466.
  • Brito C, Barral DC, Pojo M. Subversion of Ras Small GTPases in Cutaneous Melanoma Aggressiveness. Front Cell Dev Biol. 2020 Sep 23;8:575223. doi: 10.3389/fcell.2020.575223.
  • Casalou C, Ferreira A, Barral DC. The Role of ARF Family Proteins and Their Regulators and Effectors in Cancer Progression: A Therapeutic Perspective. Front Cell Dev Biol. 2020 Apr 21;8:217. doi: 10.3389/fcell.2020.00217.
  • Moreiras H, Pereira FJC, Neto MV, Bento-Lopes L, Festas TC, Seabra MC, Barral DC. The exocyst is required for melanin exocytosis from melanocytes and transfer to keratinocytes. Pigment Cell Melanoma Res. 2020 Mar;33(2):366-371. doi: 10.1111/pcmr.12840.
  • Casalou C, Faustino A, Silva F, Ferreira IC, Vaqueirinho D, Ferreira A, Castanheira P, Barona T, Ramalho JS, Serpa J, Félix A, Barral DC. Arl13b Regulates Breast Cancer Cell Migration and Invasion by Controlling Integrin-Mediated Signaling. Cancers (Basel). 2019 Sep 29;11(10):1461. doi: 10.3390/cancers11101461.
  • Kuhns S, Seixas C, Pestana S, Tavares B, Nogueira R, Jacinto R, Ramalho JS, Simpson JC, Andersen JS, Echard A, Lopes SS, Barral DC, Blacque OE. Rab35 controls cilium length, function and membrane composition. EMBO Rep. 2019 Oct 4;20(10):e47625. doi: 10.15252/embr.201847625.
  • Moreiras H, Lopes-da-Silva M, Seabra MC, Barral DC. Melanin processing by keratinocytes: A non-microbial type of host-pathogen interaction? Traffic. 2019 Apr;20(4):301-304. doi: 10.1111/tra.12638.
  • Correia MS, Moreiras H, Pereira FJC, Neto MV, Festas TC, Tarafder AK, Ramalho JS, Seabra MC, Barral DC. Melanin Transferred to Keratinocytes Resides in Nondegradative Endocytic Compartments. J Invest Dermatol. 2018 Mar;138(3):637-646. doi: 10.1016/j.jid.2017.09.042.
  • Casalou C, Faustino A, Barral DC. Arf proteins in cancer cell migration. Small GTPases. 2016 Oct;7(4):270-282. doi: 10.1080/21541248.2016.1228792.
  • Encarnação M, Espada L, Escrevente C, Mateus D, Ramalho J, Michelet X, Santarino I, Hsu VW, Brenner MB, Barral DC, Vieira OV. A Rab3a-dependent complex essential for lysosome positioning and plasma membrane repair. J Cell Biol. 2016 Jun 20;213(6):631-40. doi: 10.1083/jcb.201511093.
  • Seixas C, Choi SY, Polgar N, Umberger NL, East MP, Zuo X, Moreiras H, Ghossoub R, Benmerah A, Kahn RA, Fogelgren B, Caspary T, Lipschutz JH, Barral DC. Arl13b and the exocyst interact synergistically in ciliogenesis. Mol Biol Cell. 2016 Jan 15;27(2):308-20. doi: 10.1091/mbc.E15-02-0061.
  • Casalou C, Seixas C, Portelinha A, Pintado P, Barros M, Ramalho JS, Lopes SS, Barral DC. Arl13b and the non-muscle myosin heavy chain IIA are required for circular dorsal ruffle formation and cell migration. J Cell Sci. 2014 Jun 15;127(Pt 12):2709-22. doi: 10.1242/jcs.143446.
  • Tarafder AK, Bolasco G, Correia MS, Pereira FJC, Iannone L, Hume AN, Kirkpatrick N, Picardo M, Torrisi MR, Rodrigues IP, Ramalho JS, Futter CE, Barral DC, Seabra MC. Rab11b mediates melanin transfer between donor melanocytes and acceptor keratinocytes via coupled exo/endocytosis. J Invest Dermatol. 2014 Apr;134(4):1056-1066. doi: 10.1038/jid.2013.432.
  • VIBes in Biosciences Travel Award 2020 (Leuven, Belgium) to Andreia Ferreira
  • European Society for Pigment Cell Research Travel Award 2018 (Rennes, France) to Hugo Moreiras
  • International Federation of Pigmented Cell Societies Travel Award 2017 (Denver, USA) to Hugo Moreiras
Collaboration between multiple NMS labs leads to joint publication

Research carried out by several of our laboratories is supported by the LYSOCIL project and has been published in Traffic magazine.

LYSOCIL project on rare diseases has its final conference

The final conference of the LYSOCIL project took place on the 8th and 9th of April at the Hotel Vila Galé in Cascais. It featured presentations from the various project partners and collaborators worldwide, including Italy and Germany.

NMS Research with full representation at Ciência 2022

NOVA Medical School will be present at Ciência 2022, the largest meeting of Science and Technology in Portugal, with full representation of its research with its four Research Units and three Associate Laboratories, during for the entire duration of the event at Centro de Congressos de Lisboa.


NMS Researchers Lead Knowledge Regarding Melanin Transfer in Cells

The research, carried out by Membrane Traffic in Disease laboratory, led by Duarte Barral, is on the cover of the latest issue of Traffic magazine, a scientific journal dedicated to intracellular transport in disease.

NMS Researchers unveil new melanin regulation pathway

The group led by Duarte Barral, Membrane Traffic in Disease lab, describes a new way of regulating melanin, elucidating the transfer of pigment between human skin cells.

  • Miguel Seabra, Centro de Estudos de Doenças Crónicas (CEDOC)
  • Susana Lopes, Centro de Estudos de Doenças Crónicas (CEDOC)
  • Cláudia Almeida, Centro de Estudos de Doenças Crónicas (CEDOC)
  • Henrique Girão, Instituto de Investigação Clínica e Biomédica de Coimbra (ICBR)
  • Marta Pojo, Instituto Português de Oncologia de Lisboa Francisco Gentil (IPOLFG)
  • Jacinta Serpa, Centro de Estudos de Doenças Crónicas (CEDOC) e Instituto Português de Oncologia Francisco Gentil (IPOLFG)
  • Abel Oliva, Instituto de Tecnologia Química e Biológica António Xavier (ITQB NOVA)
  • Rune Matthiesen, Centro de Estudos de Doenças Crónicas (CEDOC)

Principal Investigator

Duarte C. Barral
Principal Investigator


Cristina Escrevente
Post-Doctoral Researcher
Andreia Ferreira
PhD Student
Liliana Lopes
PhD Student
Luís Cabaço
PhD Student
Rui Bastos
PhD Student
Cristina Demelas
MSc Student
Isabel Sesifredo
MSc Student