Alternative first exon splicing regulates subcellular distribution of methionine sulfoxide reductases.
BACKGROUND
Methionine sulfoxide reduction is an important protein repair pathway that protects against oxidative stress, controls protein function and has a role in regulation of aging. There are two enzymes that reduce stereospecifically oxidized methionine residues: MsrA (methionine-S-sulfoxide reductase) and MsrB (methionine-R-sulfoxide reductase). In many organisms, these enzymes are targeted to various cellular compartments. In mammals, a single MsrA gene is known, however, its product is present in cytosol, nucleus, and mitochondria. In contrast, three mammalian MsrB genes have been identified whose products are located in different cellular compartments.


RESULTS
In the present study, we identified and characterized alternatively spliced forms of mammalian MsrA. In addition to the previously known variant containing an N-terminal mitochondrial signal peptide and distributed between mitochondria and cytosol, a second mouse and human form was detected in silico. This form, MsrA(S), was generated using an alternative first exon. MsrA(S) was enzymatically active and was present in cytosol and nucleus in transfected cells, but occurred below detection limits in tested mouse tissues. The third alternative form lacked the active site and could not be functional. In addition, we found that mitochondrial and cytosolic forms of both MsrA and MsrB in Drosophila could be generated by alternative first exon splicing.


CONCLUSIONS
Our data suggest conservation of alternative splicing to regulate subcellular distribution of methionine sulfoxide reductases.
Kim
Hwa-Young
HY
Department of Biochemistry, University of Nebraska, Lincoln, Nebraska 68588, USA. hkim3@unl.edu
Gladyshev
Vadim N
VN
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D002467:Cell Nucleus / Q000201:enzymology; D003600:Cytosol / Q000201:enzymology; D004331:Drosophila melanogaster / Q000201:enzymology / Q000235:genetics; D005091:Exons; D006801:Humans; D051150:Methionine Sulfoxide Reductases; D051379:Mice; D008969:Molecular Sequence Data; D010088:Oxidoreductases / Q000032:analysis* / Q000235:genetics* / Q000378:metabolism
D010088:Oxidoreductases; D051150:Methionine Sulfoxide Reductases; C027219:methionine sulfoxide reductase