Molecular determinants of the subcellular localization of the Drosophila Bcl-2 homologues DEBCL and BUFFY.
The Bcl-2-family of proteins localize to intracellular membranes via a C-terminal hydrophobic membrane anchor (MA) domain, to exert their antiapoptotic or proapoptotic functions. In Drosophila, both Bcl-2 family members, DEBCL and BUFFY, contain an MA. In DEBCL the MA is necessary for the localization of protein to mitochondria and for its proapoptotic activity. BUFFY is highly similar to DEBCL but its localization and function are not clearly defined. Here, we report on comparative analysis of BUFFY and DEBCL to decipher the molecular basis for their subcellular localization. We show that these two proteins localize to distinct intracellular membranes, DEBCL predominantly to mitochondria and BUFFY to endoplasmic reticula (ER). Our results suggest that the MA-flanking residues in DEBCL, homologous to Bcl-X(L), are required for the targeting of DEBCL to mitochondria. The C-terminal positively charged residues present in DEBCL are absent in BUFFY, which allows for its localization to ER. The MA in both proteins is required for the correct targeting and proapoptotic activities of these proteins. Interestingly, a functional nuclear localization signal was identified in the N-terminal region of BUFFY and in the absence of the MA, BUFFY accumulated in the nucleus. The functional implications of these findings are discussed.
Doumanis
J
J
Hanson Institute, IMVS, Frome Road, Adelaide, Australia.
Dorstyn
L
L
Kumar
S
S
D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis; D019556:COS Cells; D002467:Cell Nucleus / Q000378:metabolism; D002522:Chlorocebus aethiops; D029721:Drosophila Proteins / Q000737:chemistry / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000378:metabolism; D006801:Humans; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism*; D051379:Mice; D051336:Mitochondrial Membranes / Q000378:metabolism; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D041681:NIH 3T3 Cells; D019913:Nuclear Localization Signals / Q000378:metabolism; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000737:chemistry* / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013347:Subcellular Fractions / Q000378:metabolism; D051020:bcl-X Protein / Q000737:chemistry / Q000378:metabolism
C477358:Buffy protein, Drosophila; D029721:Drosophila Proteins; D008565:Membrane Proteins; D050505:Mutant Proteins; D019913:Nuclear Localization Signals; D019253:Proto-Oncogene Proteins c-bcl-2; D051020:bcl-X Protein; C404322:debcl protein, Drosophila