Esta web utiliza cookies. Si continúas navegando consideramos que aceptas su uso.
Más información
Aceptar
I Jornadas Científicas del IMIB-Arrixaca
Acceso Personal
Contacto
Aviso Legal
Inicio
Bienvenida
Comités
Ponencias
Comunicaciones
Programa
Fechas clave
Inscripciones
Selección comunicaciones
Enviar comunicación
Patrocinadores
Sede
Imprimir
MGRN1: A KEY REGULATOR OF THE MELANOSOMAL PH AND HYPOPIGMENTATION UPON ORGANELLE ACIDIFICATION
Autores:
JULIA SIRÉS CAMPOS
,
MARÍA CASTEJÓN GRIÑÁN
,
MARTA ABRISQUETA GONZÁLEZ
, IDOYA MARÍA MARTÍNEZ VICENTE,
CECILIA MARÍA HERRAIZ SERRANO
,
CELIA JIMENEZ-CERVANTES FRIGOLS
,
JOSE CARLOS GARCIA-BORRON MARTINEZ
,
MARÍA CONCEPCIÓN OLIVARES SÁNCHEZ
,
Grupos de investigación:
[GI/IMIB/C010/2011] Control molecular de la proliferación y diferenciación
Comunicación:
Antecedentes:
Tyrosinase (Tyr) is the rate-limiting enzyme of melanogenesis, the biochemical pathway responsible for synthesis of melanin pigments within skin melanocytes. Melanin has a critical role in photoprotection due to its ability to absorb ultraviolet radiation. Melanocortin 1 receptor is the major determinant of mammalian pigmentation, and its signaling is highly regulated by intracellular protein partners such as mahogunin (Mgrn1), an E3-ubiquitin ligase mutated in mahoganoid mice. This mutation causes fur darkening, congenital heart defects, high embryonic lethality and spongiform neurodegeneration. We investigated the mechanisms of hyperpigmentation in Mgrn1-null melan-md1 melanocytes, compared with control melan-a6 cells.
Métodos:
In order to analyze the molecular mechanisms responsible for the differences observed in pigmentation in the two cell lines mentioned before, we used a combination of biochemical, cellular and molecular biology techniques, such as microarray experiments, SDS-PAGE and Western blot, enzymatic activity measurements by radiometric and colorimetric methods, RT-PCR and fluorescent and confocal microscopy.
Resultados:
On the basis of the differences observed, we explored the possible role of Mgrn1 in modifying tyrosinase (Tyr) expression, the rate-limiting melanogenic enzyme, or the melanosomal biochemical and/or physicochemical characteristics, resulting in post-transcriptional activation of the enzyme. To identify possible genes/proteins involved in this process, we compared gene expression profiles in both cell lines. This confirmed similar expression of melanogenic enzymes. However, we observed that Tyr activity is higher in melan-md1 cells when measured in live cells, but not in in vitro assays, although Tyr protein levels are comparable in control and mahoganoid cells. We found significant changes in genes involved in organelle biogenesis and acidification, like solute carriers and ion channels, suggesting a different ionic composition and/or pH in the melanosomal lumen of melan-a6 and –md1 cells. We confirmed that melanosomal pH is lower in melan-a6 compared with melan-md1 cells by DAMP staining of the melanosomes of both cell lines (a probe that is retained in acidic organelles). Furthermore, significant activation of Tyr and DAMP staining decrease was found for melan-a6 cells treated with neutralizing agents known to alkalinize organelles of the lysosome lineage, such as NH4Cl. Accordingly, a Mgrn1-mediated regulation of melanosome pH likely accounts for hyperpigmentation in mahoganoid melanocytes.
Conclusiones:
1. Tyrosine hydroxylase activity is higher in live melan-md1 cells compared with control melanocytes with no significant differences in a cell-free extract assay. 2. Changes in Tyr mRNA and protein levels do not account for these observations. 3. Expression of certain solute carriers and H+ transporters are strongly upregulated in melan-md1 cells. 4. Melanosomal pH, estimated by DAMP or acridine orange staining, is acidic in melan-a6 compared with -md1 cells. 5. Treatment of melan-a6 cells with lysosomotropic agents impaired DAMP staining and increased Tyr activity in vivo. The effect of such treatment on melan-md1 cells was much lower.
Instituto de Investigación Sanitaria Acreditado
Inicio
Grupo de Investigación
Miembros
Proyectos
Colaboraciones
Servicios
Recursos formativos
Producción Científica
Publicaciones
Tesis
Novedades
Noticias
Eventos
Convocatorias
Agenda