BID: a novel BH3 domain-only death agonist.

Abstract

The BCL-2 family of proteins consists of both antagonists (e.g., BCL-2) and agonists (e.g., BAX) that regulate apoptosis and compete through dimerization. The BH1 and BH2 domains of BCL-2 are required to heterodimerize with BAX and to repress cell death; conversely, the BH3 domain of BAX is required to heterodimerize with BCL-2 and to promote cell death. To extend this pathway, we used interactive cloning to identify Bid, which encodes a novel death agonist that heterodimerizes with either agonists (BAX) or antagonists (BCL-2). BID possesses only the BH3 domain, lacks a carboxy-terminal signal-anchor segment, and is found in both cytosolic and membrane locations. BID counters the protective effect of BCL-2. Moreover, expression of BID, without another death stimulus, induces ICE-like proteases and apoptosis. Mutagenesis revealed that an intact BH3 domain of BID was required to bind the BH1 domain of either BCL-2 or BAX. A BH3 mutant of BID that still heterodimerized with BCL-2 failed to promote apoptosis, dissociating these activities. In contrast, the only BID BH3 mutant that retained death promoting activity interacted with BAX, but not BCL-2. This BH3-only molecule supports BH3 as a death domain and favors a model in which BID represents a death ligand for the membrane-bound receptor BAX.

Bcl-xS and Bax induce different apoptotic pathways in PC12 cells

“…The diminution most probably represents Bcl-x S -induced apoptosis, as studies from other laboratories as well as ours have established that the expression of reporter genes is eliminated in cells undergoing apoptosis ( Figure 3B and see, e.g., Wang et al, 1996). The ability of the anti-apoptotic proteins Bcl-2 and Bcl-x L to inhibit the Bcl-x S e ect, and the need of the latter for caspase activity, further support the notion that overexpression of Bcl-x S induces apoptosis in transfected PC12 cells.…”

“…The need for caspase activity was also reported in the induction of apoptosis by transient overexpression of some other anti-apoptotic members of the Bcl-2 family of proteins, for example Bid (Wang et al, 1996), Bak and Bik (Orth and Dixit, 1997) and Bok (Hsu et al, 1997).…”

“…The results showed that the mI-3 and the DC22 mutants are e ective in this regard. It was previously shown that the mI-3 mutation causes Bcl-2 to lose its capacity for heterodimerization with Bax (St. Clair et al, 1997;Yin et al, 1994) and Bid (Wang et al, 1996). The ability of the mI-3 Bcl-2 mutant to inhibit Bcl-x Sinduced cell death thus demonstrates that this mutation does not eliminate the anti-apoptotic e ect of Bcl-2, at least with respect to apoptosis induced by Bcl-x S .…”

Dexamethasone protects primary cultured hepatocytes from death receptor-mediated apoptosis by upregulation of cFLIP

“…Rabbit polyclonal anti-Bid antibody was prepared using full-length mouse Bid. 44 All other reagents were purchased from Sigma, unless indicated otherwise.…”

Downregulation of Bid is associated with PKCɛ-mediated TRAIL resistance

“…7 Cross-talk between the receptormediated pathway and mitochondria occurs when active caspase-8 cleaves Bid and the truncated Bid translocates to the mitochondria causing activation of Bax/Bak, release of cytochrome c and activation of caspases. [8][9][10][11] Downregulation/mutations in caspase-8 or increased expression of FLIP can contribute to TRAIL resistance. 3,[12][13][14][15] The presence of antiapoptotic proteins, such as Akt or Bcl-2 family members can also contribute to TRAIL resistance by affecting either the extrinsic or the intrinsic cell death pathway.…”