The resident endoplasmic reticulum protein, BAP31, associates with gamma-actin and myosin B heavy chain.
BAP31 is a 28-kDa integral membrane protein of the endoplasmic reticulum whose cytosolic domain contains two caspase recognition sites that are preferentially cleaved by initiator caspases, such as caspase-8. Recently, we reported that the caspase-resistant BAP31 inhibited Fas-mediated apoptotic membrane fragmentation and the release of cytochrome c from mitochondria in KB epithelial cells (Nguyen M., Breckenridge G., Ducret A & Shore G. (2000) Mol. Cell. Biol.20, 6731-6740). We describe here the characterization by capillary liquid chromatography microelectrospray tandem MS of a BAP31 immunocomplex isolated from a HepG2 cell lysate in the absence of a death signal. We show that BAP31 specifically associates with nonmuscle myosin heavy chain B and nonmuscle gamma-actin, two components of the cytoskeleton actomyosin complex. Collectively, these data confirm that BAP31, in addition to its potential role as a chaperone, may play a fundamental role in the structural organization of the cytoplasm. Here we also show that Fas stimulation of apoptosis releases BAP31 associations with these motor proteins, a step that may contribute to extranuclear events, such as membrane remodelling, during the execution phase of apoptosis.
Ducret
Axel
A
Merck Frosst Center for Therapeutic Research, Pointe-Claire-Dorval, Québec, Canada. axel.ducret@roche.com
Nguyen
Mai
M
Breckenridge
David G
DG
Shore
Gordon C
GC
D000199:Actins / Q000235:genetics / Q000378:metabolism*; D000205:Actomyosin / Q000378:metabolism; D000595:Amino Acid Sequence; D002853:Chromatography, Liquid; D004591:Electrophoresis, Polyacrylamide Gel; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D018995:Myosin Heavy Chains / Q000235:genetics / Q000378:metabolism*; D024501:Nonmuscle Myosin Type IIB; D010446:Peptide Fragments / Q000378:metabolism; D011233:Precipitin Tests
D000199:Actins; C091247:BCAP31 protein, human; D008565:Membrane Proteins; D010446:Peptide Fragments; D000205:Actomyosin; D024501:Nonmuscle Myosin Type IIB; C103815:nonmuscle myosin type IIB heavy chain; D018995:Myosin Heavy Chains