The anti-apoptotic protein L(*) of Theiler's murine encephalomyelitis virus (TMEV) contains a mitochondrial targeting signal.
L(*) protein of TMEV is out-of-frame with the viral polyprotein from an alternative initiation codon AUG, 13 nucleotides downstream from the authentic polyprotein AUG. Anti-apoptotic activity of L(*) was demonstrated by both 'loss of function' and 'gain of function' experiments. However, the precise mechanism(s) of anti-apoptotic activity of L(*) remains to be clarified. In this study, L(*) was demonstrated to be localized to mitochondria. It was also shown by the GFP fusion protein that N-terminal sequence of L(*) may contain a mitochondrial targeting signal (MTS). Surprisingly, L(*)((5-70))-GFP and L(*)((41-70))-GFP were localized to mitochondria although L(*)((1-70))-GFP was distributed in the cytosol, suggesting L(*) has an MTS between amino acid (AA) positions 41 and 70, and that L(*)((1-4)) inhibits its mitochondrial targeting. Furthermore, L(*)((1-70))-GFP was localized to the mitochondria by co-expression of L(*)((65-156)), indicating that L(*)((65-156)) suppresses the inhibition of mitochondrial targeting by L(*)((1-4)). These results suggest that the intra- or inter-molecular interaction of L(*) regulates its mitochondrial localization. It is also suggested that L(*) may inhibit the intrinsic apoptosis through the localization to mitochondria.
Department of Microbiology, Kanazawa Medical University School of Medicine, 1-1 Uchinada, Ishikawa 920-0293, Japan.
Toshiki
T
Himeda
Takako
T
Okuwa
Masafumi
M
Nojiri
Yasushi
Y
Muraki
Yoshiro
Y
Ohara
D000595:Amino Acid Sequence; D000818:Animals; D051017:Apoptosis Regulatory Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D002460:Cell Line; D006224:Cricetinae; D042541:Intracellular Space / Q000378:metabolism; D051379:Mice; D008928:Mitochondria / Q000378:metabolism*; D021381:Protein Transport; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D017945:Theilovirus / Q000235:genetics* / Q000378:metabolism*; D014764:Viral Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
D051017:Apoptosis Regulatory Proteins; D011993:Recombinant Fusion Proteins; D014764:Viral Proteins