Elsevier

Molecular Immunology

Volume 38, Issue 1, January 2001, Pages 65-72
Molecular Immunology

An alternatively spliced long form of Fas apoptosis inhibitory molecule (FAIM) with tissue-specific expression in the brain

https://doi.org/10.1016/S0161-5890(01)00035-9Get rights and content

Abstract

The gene encoding Fas apoptosis inhibitory molecule (FAIM) was cloned by differential display using RNA obtained from Fas-resistant and Fas-sensitive primary murine B lymphocytes. FAIM is highly evolutionarily conserved and broadly expressed, suggesting that its gene product plays a key role in cellular physiology. Here we report the identification of a new, longer form of FAIM (FAIM-L) and characterization of the genomic locus that clarifies its origin. The murine FAIM gene is located at chromosome 9f1, a region syntenic to the corresponding location of the human FAIM gene. The gene consists of six exons and contains putative translation initiation sites within exons II and III. The long form of FAIM is generated by all six exons, whereas the originally cloned form of FAIM, now termed FAIM-Short (FAIM-S) is generated from five exons by alternative splicing. FAIM-L is dominantly expressed in the brain whereas FAIM-S is widely expressed in many tissues.

Introduction

Many TNFR family members can mediate signaling for apoptosis. Among these receptors, Fas appears to play a key role in immune homeostasis, inasmuch as mutation or deletion of Fas is manifested by autoimmunity, and lymphoproliferation, both in mouse and human (Watanabe-Fukunaga et al., 1992, Fisher et al., 1995, Rieux-Laucat et al., 1995). A number of studies have shown that the absence of functional Fas produces an autoimmune B cell dyscrasia distinct from the effects of Fas mutation on other immune cells (Perkins et al., 1987, Nemazee et al., 1991, Fukuyama et al., 1998, Sobel et al., 1998). This may relate to the role of Fas-mediated apoptosis in deleting autoreactive B cells (Rathmell et al., 1995, Rathmell et al., 1996).

B cells are not uniformly susceptible to Fas-mediated apoptosis. Rather, the level of Fas-sensitivity is modulated by specific receptor signaling. CD40 engagement upregulates Fas expression and induces marked sensitivity to Fas-dependent killing, whereas sIg crosslinking, or IL-4R binding, produces resistance to Fas mediated apoptosis, even in otherwise susceptible, CD40L-stimulated B cell targets (Garrone et al., 1995, Rothstein et al., 1995, Schattner et al., 1995, Foote et al., 1996a, Foote et al., 1996b, Lagresle et al., 1996, Rathmell et al., 1996). sIg-induced Fas-resistance requires NF-κB and depends on macromolecular synthesis, suggesting that new gene expression is involved (Foote et al., 1996a, Foote et al., 1996b) (Schram and Rothstein, manuscript in preparation). Among previously identified anti-apoptotic molecules, Bcl-xL and c-FLIP appear to function as terminal effector molecules, inasmuch as expression of each is upregulated coordinately with induction of Fas-resistance, and overexpression protects primary B cells and/or B cell lines from Fas killing (Schneider et al., 1997, Van Parijs et al., 1999, Wang et al., 2000; Schram and Rothstein, unpublished observations). Identification of additional, previously unknown, effector molecules was sought by comparing transcripts expressed in Fas-resistant and Fas-sensitive primary B cells, utilizing differential display analysis (Liang and Pardee, 1992). This led to the cloning and sequencing of a completely novel gene that encodes a Fas apoptosis inhibitory molecule (FAIM) (Schneider et al., 1999). FAIM expression is upregulated in B cells by anti-Ig treatment that induces Fas-resistance, and overexpression of FAIM diminishes sensitivity to Fas-mediated apoptosis of B and non-B cell lines (Schneider et al., 1999 and unpublished observations).

The predicted 179 amino acid sequence of FAIM is highly evolutionarily conserved and FAIM is widely expressed in murine tissues, suggesting that FAIM plays an important role in cellular physiology (Schneider et al., 1999). Here we report the discovery of a novel, long form of FAIM that results from alternative splicing. The two forms of FAIM, FAIM-Long (FAIM-L) and FAIM-Short (FAIM-S) are differentially expressed; in contrast to FAIM-S, expression of FAIM-L is highly tissue-specific and strictly limited to brain and testes.

Section snippets

cDNA library screening

Partial FAIM transcripts were identified by differential display, comparing RNA samples obtained from Fas-sensitive B cells stimulated with CD40L and Fas-resistant B cells treated with CD40L plus anti-Ig. Full-length FAIM (GenBank accession number: AF130367) was obtained by screening a mouse thymus cDNA library with a radiolabeled probe generated from a commercially available EST clone (W41405, Incyte Genome Systems, St. Louis, MO). The probe was also used to screen a mouse brain cDNA library

A longer isoform of FAIM (FAIM-L)

Screening of a mouse brain cDNA library revealed a number of FAIM-containing clones. One clone was found to possess a 57 bp insert 22 bp upstream of the putative FAIM start methionine (Fig. 1A), the remainder of the sequence being identical to other clones that had been previously isolated and reported for FAIM. The insertion adds 66 nucleotides (22 amino acids) to the 5′ end of FAIM (Fig. 1A). This longer FAIM isoform is now termed FAIM-L, and the previously identified, shorter form is renamed

Discussion

FAIM is a novel anti-apoptotic gene identified through differential display analysis of RNA samples obtained from inducibly Fas-resistant and Fas-sensitive primary B cells (Schneider et al., 1999). FAIM presumably fulfills a key role in cellular physiology inasmuch as it is highly evolutionarily conserved and widely expressed (Schneider et al., 1999). However, the FAIM-encoded amino acid sequence contains no recognizable effector domains and so the mechanism by which FAIM opposes Fas-mediated

Acknowledgements

This work was supported by United States Public Health Service grant AI45112 awarded by the National Institutes of Health.

References (60)

  • Y. Pekarsky et al.

    Cloning of breakpoints in 3q21 associated with hematologic malignancy

    Cancer Genet. Cytogenet.

    (1995)
  • J. Plumas et al.

    Tumor B cells from non-Hodgkin's lymphoma are resistant to CD95 (Fas/Apo-1)-mediated apoptosis

    Blood

    (1998)
  • J.C. Rathmell et al.

    Expansion or elimination of B cells in vivo: dual roles for CD40- and Fas (CD95)-ligands modulated by the B cell antigen receptor

    Cell

    (1996)
  • Y.P. Shi et al.

    FISH probes for mouse chromosome identification

    Genomics

    (1997)
  • L. Van Parijs et al.

    Autoimmunity as a consequence of retrovirus-mediated expression of C-FLIP in lymphocytes

    Immunity

    (1999)
  • H. Yoshida et al.

    Apaf1 is required for mitochondrial pathways of apoptosis and brain development

    Cell

    (1998)
  • L. Balvay et al.

    Pre-mRNA secondary structure and the regulation of splicing

    Bioassays

    (1993)
  • V.S. Baranov et al.

    Chromosomal localization of ceruloplasmin and transferrin genes in laboratory rats, mice and in man by hybridization with specific DNA probes

    Chromosoma

    (1987)
  • T.E. Carey et al.

    Nonrandom chromosome aberrations and clonal populations in head and neck cancer

    Anticancer Res.

    (1993)
  • J.C. Cigudosa et al.

    Cytogenetic analysis of 363 consecutively ascertained diffuse large B-cell lymphomas

    Genes Chromosomes Cancer

    (1999)
  • S.P. Cregan et al.

    Bax-dependent caspase-3 activation is a key determinant in p53-induced apoptosis in neurons

    J. Neurosci.

    (1999)
  • M. Djerbi et al.

    The inhibitor of death receptor signaling, FLICE-inhibitory protein defines a new class of tumor progression factors

    J. Exp. Med.

    (1999)
  • L.C. Foote et al.

    IL-4 induces Fas resistance in B cells

    J. Immunol.

    (1996)
  • L.C. Foote et al.

    Intracellular signaling for inducible antigen receptor-mediated Fas resistance in B cells

    J. Immunol.

    (1996)
  • J.A. Frugoli et al.

    Intron loss and gain during evolution of the catalase gene family in angiosperms

    Genetics

    (1998)
  • H. Fukuyama et al.

    Transgenic expression of Fas in T cells blocks lymphoproliferation but not autoimmune disease in MRL-lpr mice

    J. Immunol.

    (1998)
  • P. Garrone et al.

    Fas ligation induces apoptosis of CD40-activated human B lymphocytes

    J. Exp. Med.

    (1995)
  • H. Hamaguchi et al.

    Establishment of a novel human myeloid leukaemia cell line (HNT-34) with t(3;3)(q21;q26), t(9;22)(q34;q11) and the expression of EVI1 gene, P210 and P190 BCR/ABL chimaeric transcripts from a patient with AML after MDS with 3q21q26 syndrome

    Br. J. Haematol.

    (1997)
  • T.E. Hedlund et al.

    Fas-mediated apoptosis in seven human prostate cancer cell lines: correlation with tumor stage

    Prostate

    (1998)
  • C. Huerre et al.

    The structural gene for transferrin (TF) maps to 3q21–3qter

    Ann. Genet.

    (1984)
  • Cited by (40)

    • A fas apoptotic inhibitory molecule from Ruditapes philippinarum: Investigation on molecular characterization and functional analysis

      2020, Fish and Shellfish Immunology
      Citation Excerpt :

      Recently, FAIMs could be divided into two classes: FAIM long (FAIML) and FAIM short (FAIMS). In vertebrates, FAIML is almost exclusively expressed in the nervous system, which could not regulate classical survival/differentiation pathways such as PI3K, NF-κB, or ERK/MAPK, but act as a critical switch on the biological consequences derived from death-receptors triggering, overriding the apoptotic death cascades [8,9]. For FAIMS, it usually possess stable structure, and rich in β-sheets.

    • Fas apoptosis inhibitory molecule regulates T cell receptor-mediated apoptosis of thymocytes by modulating akt activation and Nur77 expression

      2010, Journal of Biological Chemistry
      Citation Excerpt :

      It is highly conserved and widely expressed, although it has no homology to other known proteins. In addition to being abundant in spleen, FAIM was also highly expressed in thymus (26), implying that FAIM could play a role in some aspects of thymocyte physiology. We had previously inactivated faim in mice and found that FAIM regulates Fas-triggered apoptosis of lymphocytes and hepatocytes by modulating cellular FLICE-like inhibitory protein expression, hence affecting the binding of caspase-8 to Fas (27).

    • Crystallization and preliminary X-ray crystallographic studies of human FAIM protein

      2010, Acta Crystallographica Section F: Structural Biology and Crystallization Communications
    View all citing articles on Scopus
    1

    Present address: The Center for Blood Research, Harvard Medical School, LMRC Room 501, 221 Longwood Avenue, Boston, MA 02115, USA.

    View full text