March-xi, a Novel Transmembrane Ubiquitin Ligase Implicated in Ubiquitin-dependent Protein Sorting in Developing Spermatids.
From: Department of Biological Sciences, Tokyo Institute of Technology, Yokohama 226-8501, Japan.
The Journal of biological chemistry
- Publish Date: Aug 2007
- ISSN: 0021-9258
- Volume: 282
- Issue: 34
- Pages: 24806-15
- Medium: Print
- Language: English
- Citation (JAMA): Morokuma Yuri, Nakamura Nobuhiro, Kato Akira, et al. March-xi, a Novel Transmembrane Ubiquitin Ligase Implicated in Ubiquitin-dependent Protein Sorting in Developing Spermatids.. J. Biol. Chem. Aug 2007;282:24806-15
Abstract
A mechanism by which ubiquitinated cargo proteins are sorted into multivesicular bodies (MVBs) from plasma and trans-Golgi network (TGN) membranes is well established in yeast and mammalian somatic cells. However, the ubiquitin-dependent sorting pathway has not been clearly defined in germ cells. In this study we identified a novel member of the transmembrane RING-finger family of proteins, termed membrane-associated RING-CH (MARCH)-XI, that is expressed predominantly in developing spermatids and weakly in brain and pituitary. MARCH-XI possesses an E3 ubiquitin ligase activity that targets CD4 for ubiquitination. Immunoelectron microscopy of rat round spermatids showed that MARCH-XI is localized to TGN-derived vesicles and MVBs. Fluorescence staining of rat round spermatids and immunoprecipitation of rat testis demonstrated that MARCH-XI forms complexes with the adaptor protein complex-1 and with fucose-containing glycoproteins including ubiquitinated forms. Furthermore, the C-terminal region of MARCH-XI mediates its interaction with mu1-adaptin and Veli through a tyrosine-based motif and a PDZ binding motif, respectively. Our data suggest that MARCH-XI acts as a ubiquitin ligase with a role in ubiquitin-mediated protein sorting in the TGN-MVB transport pathway, which may be involved in mammalian spermiogenesis.
Mesh Headings (Keywords): Amino Acid Motifs, Amino Acid Sequence, Animals, Brain, Cloning, Molecular, Male, Microscopy, Immunoelectron, Molecular Sequence Data, Pituitary Gland, Protein Binding, Rats, Recombinant Proteins, Spermatids, Ubiquitin, Ubiquitin-Protein Ligases
Check for Full Text / PubMed Unique Identifier (PMID): 17604280
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