Cytosolic prion protein is the predominant anti-Bax prion protein form: exclusion of transmembrane and secreted prion protein forms in the anti-Bax function.
Prion protein (PrP) prevents Bax-mediated cell death by inhibiting the initial Bax conformational change that converts cytosolic Bax into a pro-apoptotic protein. PrP is mostly a glycophosphatidylinositol-anchored cell surface protein but it is also retrotranslocated into cytosolic PrP (CyPrP) or can become a type 1 or type 2 transmembrane protein. To determine the form and subcellular location of the PrP that has anti-Bax function, we co-expressed various Syrian hamster PrP (SHaPrP) mutants that favour specific PrP topologies and subcellular localization with N-terminally green fluorescent protein tagged pro-apoptotic Bax (EGFP-Bax) in MCF-7 cells and primary human neurons. Mutants that generate both CyPrP and secreted PrP ((Sec)PrP) or only CyPrP have anti-Bax activity. Mutants that produce (Ctm)PrP or (Ntm)PrP lose the anti-Bax activity, despite their ability to also make (Sec)PrP. Transmembrane-generating mutants do not produce CyPrP and both normal and cognate mutant forms of CyPrP rescue against the loss of anti-Bax activity. (Sec)PrP-generating constructs also produce non-membrane attached (Sec)PrP. However, this form of PrP has minimal anti-Bax activity. We conclude that CyPrP is the predominant form of PrP with anti-Bax function. These results imply that the retrotranslocation of PrP encompasses a survival function and is not merely a pathway for the proteasomal degradation of misfolded protein.
Lin
David T S
DT
Bloomfield Center for Research in Aging, LDI, Montréal, QC, Canada H3T 1E2.
Jodoin
Julie
J
Baril
Michaël
M
Goodyer
Cynthia G
CG
Leblanc
Andréa C
AC
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism*; D006801:Humans; D051379:Mice; D009154:Mutation / Q000235:genetics; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D011328:Prions / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D051028:bcl-2-Associated X Protein / Q000037:antagonists & inhibitors* / Q000378:metabolism*
D011328:Prions; D051028:bcl-2-Associated X Protein