Lévy Frédéric, Muehlethaler Katja, Salvi Suzanne, Peitrequin Anne-Lise, Lindholm Cecilia K, Cerottini Jean-Charles, Rimoldi Donata
Ludwig Institute for Cancer Research, University of Lausanne, Epalinges, Switzerland.
Mol Biol Cell. 2005 Apr;16(4):1777-87. doi: 10.1091/mbc.e04-09-0803. Epub 2005 Feb 9.
The production of pigment by melanocytic cells of the skin involves a series of enzymatic reactions that take place in specialized organelles called melanosomes. Melan-A/MART-1 is a melanocytic transmembrane protein with no enzymatic activity that accumulates in vesicles at the trans side of the Golgi and in melanosomes. We show here that, in melanoma cells, Melan-A associates with two homologous to E6-AP C-terminus (HECT)-E3 ubiquitin ligases, NEDD4 and Itch, and is ubiquitylated. Both NEDD4 and Itch participate in the degradation of Melan-A. A mutant Melan-A lacking ubiquitin-acceptor residues displays increased half-life and, in pigmented cells, accumulates in melanosomes. These results suggest that ubiquitylation regulates the lysosomal sorting and degradation of Melan-A/MART-1 from melanosomes in melanocytic cells.
皮肤黑素细胞产生色素涉及一系列在称为黑素小体的特殊细胞器中发生的酶促反应。Melan-A/MART-1是一种无酶活性的黑素细胞跨膜蛋白,它在高尔基体反式面的囊泡和黑素小体中积累。我们在此表明,在黑色素瘤细胞中,Melan-A与两种E6-AP C末端同源(HECT)-E3泛素连接酶NEDD4和Itch相关联,并被泛素化。NEDD4和Itch都参与Melan-A的降解。缺乏泛素受体残基的突变型Melan-A半衰期延长,并且在色素细胞中积聚在黑素小体中。这些结果表明,泛素化调节黑素细胞中Melan-A/MART-1从黑素小体的溶酶体分选和降解。