| 背景 | The Bcl-2 family consists of a number of evolutionarily conserved proteins containing Bcl-2 homology domains (BH) that regulate apoptosis through control of mitochondrial membrane permeability and release of cytochrome c (1-3). Four BH domains have been identified (BH1-4) that mediate protein interactions. The family can be separated into three groups based upon function and sequence homology: pro-survival members include Bcl-2, Bcl-xL, Mcl-1, A1 and Bcl-w; pro-apoptotic proteins include Bax, Bak and Bok, and "BH3 only" proteins Bad, Bik, Bid, Puma, Bim, Bmf, Noxa and Hrk. Interactions between death-promoting and death-suppressing Bcl-2 family members has led to a rheostat model in which the ratio of pro-apoptotic and anti-apoptotic proteins controls cell fate (4). Thus, pro-survival members exert their behavior by binding to and antagonizing death-promoting members. In general, the "BH3-only members" can bind to and antagonize the pro-survival proteins leading to increased apoptosis (5). While some redundancy of this system likely exists, tissue specificity, transcriptional and post-translational regulation of many of these family members can account for distinct physiological roles.Bcl-2-like 10 (BCL2L10), known as Diva or Boo in mouse (6,7) and Bcl-B in human (8), is a Bcl-2 family member with some unique properties. Expression of the mouse mRNA was detected in multiple embryonic tissues but restricted to adult ovary and testis (6,7); human Bcl-B appears to be more widely expressed (8). BCL2L10 contains BH1, 2, and 4 domains as well as a putative carboxy-terminal transmembrane domain. While some studies report the presence of a pro-apoptotic BH3 domain in BCL2L10, conflicting reports indicate an incomplete or absent BH3 domain (7-9). Similarly, some studies indicate that BCL2L10 induces apoptosis (6,9) while other data implies a role in suppressing cell death (7,8,10). BCL2L10 may function by differentially binding other Bcl-2 family members and through interaction with the apoptosome protein Apaf-1 (6,7). Despite its restricted expression in mice, Diva knockouts were fertile and exhibit no obvious developmental defects (11). |
