SummaryStimulation of the Fas (APO-1, CD95) receptor, which is present on a variety of cells, usually triggers a process of programmed cell death. Systemic injection of anti-Fas antibody into mice leads to fulminant liver destruction resulting from massive hepatocyte apoptosis, and to rapid death. Hepatocytes bear Fas but do not express Bcl-2, a protein that plays, in a number of conditions, a protective role against apoptosis. We have generated mice whose liver expresses Bcl-2 as the result of a bcl-2 transgene placed under the control of the hepatocyte-specific otl-antitrypsin gene promoter, but is otherwise not distinguishable from that of normal mice. These mice display a marked to almost total resistance to liver damage induced by anti-Fas antibody injection. This protective effect of Bcl-2 occurs in the absence of significant variations, in the stimulated livers, in the level of expression of other proteins also involved in resistance or sensitivity to apoptosis, namely Bcl-x, Bax, Bad, Bak, and p53. Mice with protected livers, however, die almost as rapidly as normal mice, which indicates that acute lethality results from stimulation of Fas receptors present on other target organs or cells.

In the mouse, opening of the vaginal cavity to the skin is a late event, occurring around the fifth week of life; it can be induced in sexually immature mice by beta-estradiol injections. We have generated two lines of transgenic mice expressing the human Bcl2 protein in a variety of tissues. The vaginal cavity of the transgenic females remained permanently closed, a condition completely resistant to beta-estradiol injections; this was accompanied by a considerable distension of the genital tract. Histologic studies of vaginal sections at the time of opening to the skin in normal mice showed, by the TUNEL method which detects nuclei with fragmented DNA characteristic of apoptosis, that this event coincides with extensive apoptosis in the lower part of the vaginal mucosa, a process prevented in the bcl2 transgenic mice, which express Bcl2 in suprabasal epithelial cells and in subepithelial cells of the vaginal mucosa. In contrast, two lines of mice bearing a Bcl2 transgene placed under the control of a K10 keratin promoter, whose expression is restricted to the suprabasal layers of the epidermis, had a normal phenotype. Eyelids' formation and opening of the external ear canals, which also occur after birth in the mouse, were not altered in any of these transgenic lines; histological study of eye and ear sections at the time of these events failed to detect apoptosis. In conclusion, the tissue remodeling required to complete maturation of the mouse female genital tract at the time of puberty is an hormonally triggered apoptosis-dependent process.

B-non-Hodgkin lymphomas (B-NHLs IntroductionHuman lymphomas develop mainly from B lymphocytes after chromosomal translocations involving the IgH promoter and an oncogene, 1,2 but the type-specific molecular basis for lymphoma cell proliferation remains largely unknown. 1 It was recently suggested that, in B-cell lymphomas, CD40 and its ligand CD154 were coexpressed and associated in a raft-based signalosome leading to constitutive expression of Considering that the Lyn Src-family kinase and the Cbp/PAG adaptor are the major phosphotyrosylated proteins of lymphoma rafts, 4,5 and therefore components of a proximal signaling platform, 6 we set out to investigate their membrane organization and oncogenic potential in a panel of human B/T non-Hodgkin and Hodgkin lymphoma cell lines and tissues.In normal lymphocytes, the Csk-binding protein (Cbp)/ phosphoprotein associated with glycosphingolipid-enriched microdomains (PAG) adaptor 7-9 is a major phosphotyrosylated protein involved in the negative regulation of signaling in murine T lymphocytes [10][11][12][13] and mast cells. 14 Cbp/PAG (hereafter PAG), phosphorylated at tyrosine 317, was shown to bind Csk 15 and allow phosphorylation of the Src-kinase C-terminal regulatory tyrosine and inactivation of the Src kinase. 16,17 PAG is tyrosine phosphorylated in resting T lymphocytes and rapidly dephosphorylated upon activation. 10,11,16,17 Likewise, tyrosine phosphorylated PAG associated with Csk was shown to inhibit bovine B lymphocyte proliferation. 18 In contrast, several human B-non-Hodgkin lymphoma (B-NHL) cell lines proliferate with a tyrosine phosphorylated PAG adaptor, 4 suggesting that, in lymphoma cells, this form of PAG rather promotes proliferation.PAG is a 432-amino acid protein localized in sphingolipidenriched membrane microdomains. 19 The cytoplasmic portion of the PAG single transmembrane protein contains 10 phosphorylatable tyrosines and 2 proline-rich domains (residues 131-138 and 257-263), to potentially interact with SH2 and SH3 domains, respectively. Palmitoylation facilitates PAG association with rafts 8 and contributes to the formation of a "lipid shell" around PAG in sphingolipid and cholesterol-rich domains. 20 We investigated how PAG, Lyn, and Csk interact within membrane microdomains in B-NHLs (Burkitt, follicular, mantle cell, and diffuse large B-cell lymphomas of both germinal centerand activated B cell-type), anaplastic large cell T lymphomas (ALCLs) expressing the nucleophosmin-anaplastic lymphoma kinase (NPM-ALK) fusion protein (ALK ϩ lymphomas) and Hodgkin lymphoma-derived cell lines and tissues. The PAG protein was expressed in all those cells, but only in B-NHL lines did the phosphorylated PAG protein associate with sphingolipid-enriched membrane domains (or rafts) and strongly interact with Lyn. The phosphorylated signal transducer and activator of transcription 3 (STAT3) was also part of the Lyn/PAG raft complex in B-NHL lines and tissues and may modulate gene expression under the control of the Lyn/PAG signalosome. The online versio...

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