Sorting and secretion of a melanosome membrane protein, gp75/TRP1.
J Invest Dermatol
; 109(6): 788-95, 1997 Dec.
Article
em En
| MEDLINE
| ID: mdl-9406822
ABSTRACT
The melanosome is an organelle specialized for melanin synthesis that is derived from the endocytic pathway. Several melanosome membrane proteins have been identified, forming a family of proteins known as tyrosinase-related proteins. Two members of this family, tyrosinase and gp75, are well-characterized melanocyte differentiation antigens. Our previous studies have shown that gp75, the mouse brown locus protein, is sorted to melanosomes along the endocytic pathway, directed by a hexapeptide sorting signal located in the cytoplasmic tail. In this study, we report the unexpected finding that a portion of gp75 is secreted. Substantial levels of secretory gp75 were detected in melanocytic cells. Cell surface expression of gp75 was also detected, representing 2% of cellular gp75. Characterization of secretory gp75 cells showed that it is (i) a truncated form that lacks the transmembrane region, the cytoplasmic tail where the endosomal sorting signal is located, and a small portion of the lumenal domain; (ii) more extensively glycosylated than endocytic/melanosomal gp75, containing trans-Golgi processed sugar residues; and (iii) generated post-translationally in an acid sensitive compartment after processing in the trans-Golgi, and secreted rapidly after generation. Thus, these endocytic/melanosomal membrane proteins can be processed to abundant secretory forms, probably in an endocytic compartment through a potentially novel secretory pathway.
Buscar no Google
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Oxirredutases
/
Glicoproteínas de Membrana
/
Proteínas
/
Melanócitos
/
Proteínas de Membrana
Tipo de estudo:
Prognostic_studies
Limite:
Animals
Idioma:
En
Revista:
J Invest Dermatol
Ano de publicação:
1997
Tipo de documento:
Article
País de afiliação:
Estados Unidos