Genetic polymorphisms of Fas (CD95) and FasL (CD178) in human longevity: studies on centenarians

M Pinti1, L Troiano1, M Nasi1, L Moretti1, E Monterastelli1, A Mazzacani1, C Mussi2, P Ventura2, F Olivieri3, C Franceschi3,4, G Salvioli2 and A Cossarizza*,1

apoptosis can be predicted in aging, where changes in the balance between cell proliferation/activation and cell loss are frequent.1–3 Such changes determine some characteristic features of immunosenescence, such as thymic involution, skewing of T cell repertoire, accumulation of memory/effector T cells and autoimmune phenomena, among others.4–8

Department of Biomedical Sciences, University of Modena and Reggio via Campi

,

Modena, Italy

Department of Internal Medicine, University of Modena and Reggio Emilia, Ospedale Estense,

Modena, Italy

Department of Gerontological Studies, INRCA, via Birarelli

,

Italy

Department of Experimental Pathology, University of Bologna, via San Giacomo

,

Bologna, Italy * Corresponding author: Andrea Cossarizza, MD P

, Department of Biomedical Sciences, Section of General Pathology, via Campi,

,

Modena, Italy. Tel: +

; Fax: +

; E-mail: cossariz@unimo.it

One of the most important apoptotic pathways is that triggered by CD95 (Fas/Apo-1), a type 1 transmembrane protein belonging to the tumor necrosis factor (TNF) receptor superfamily.9 Fas regulates several immune processes, including selection of T cell repertoire, deletion of self-reactive cells and cytotoxicity against target cells or tissues, among others.10–14 Fas is present on the cell surface as a monomeric protein, and can be bound by its natural ligand, called Fas ligand (FasL, CD178), a protein member of TNF superfamily.15 Cross-linking of Fas by FasL leads to trimerization of death domain (DD) of Fas in the inner membrane surface; the trimeric Fas recruits an adapter protein, the Fas associated DD (FADD), by homotypic protein-protein interaction, forming a death- inducing signaling complex (DISC). FADD then recruits procaspase 8 to the DISC by homotypic interaction between their death effector domains (DED). Procaspase 8 is autolytically cleaved into active caspase 8, which activates caspase 3, and starts a complex signaling pathway that leads to apoptosis.16,17

Received 2.5.01; revised 1.10.01; accepted 2.10.01 Edited by PH Krammer

Abstract

evidenced by the increased expression of Fas in lymphocytes from aged people. However, little is known about the genetic regulation of Fas and its ligand, FasL. We have studied their polymorphismsin50centenariansand86youngdonorsliving in Northern Italy. The first Fas polymorphism, at position 7670,hasinCaucasianaheterozigosityof51%;thesecond,at 71377 position, has the wild type allele (G) with a very high frequency (83%) respect to the mutant allele. Genotype and allele distribution for both polymorphisms were similar in controlsandcentenarians.Similarresultswerefoundasfaras two FasL polymorphisms (IVS2nt-124 and IVS3nt169) are concerned. On the whole, our data suggest that Fas and FasL polymorphisms, as well as their haplotypes, are unlikely to be associated with successful human longevity.

Fas, whereas activated memory T cells express relatively high levels of Fas. This has been linked to the higher susceptibility of memory cells to undergo apoptosis, and further underlines the role of Fas in the homeostasis of the immune system.14

studies on the expression of Fas in human aging and longevity, and different authors have shown that the number of Fas+T cells increases with age.18–21 Fas expression seems to increase both in CD4+ and CD8+ cells, this increase being present either in naı¨ve (CD45RA+,CD62L+) or memory T lymphocytes (CD45R0+,CD62L7), suggesting that the shift from na¨ıve to memory is not uniquely responsible for this phenomen- on.20 Such an upregulation, along with a reduced expression of bcl-2, has been correlated to the existence of an age-related increased susceptibility to apoptosis both in CD4 and CD8 T cells.22 However, little is known about the molecular mechanism that modifies the expression of Fas in lymphocytes of elderly subjects, nor of its transcriptional regulation, and it is not known whether and how aging influences the activity of this gene.

CellDeathandDifferentiation(2002)9,431–438.DOI:10.1038/sj/ cdd/4400964

Keywords: apoptosis; CD95/Apo-1/Fas gene; CD178/FasL gene polymorphism; aging

Abbreviations: RFLP, restriction fragment length polymorphism; ASA, allele specific amplification; ACRS, amplification created restriction site

Introduction

flanking region of the human Apo-1/Fas gene.23 The first is located 670 bp upstream from the translational start site of the gene, on the binding site of the transcription factors

functions and pathological processes, including the homeostasis of the immune system. An important role of

This polymorphism is an A to G substitution that creates a restriction site for MvaI and is therefore called MvaI restriction fragment length polymorphism (RFLP). This polymorphism is common in the normal Caucasian popula- tion, with a frequency of 0.49 for allele G and 0.51 for the allele A. The second polymorphism is a G to A substitution at position 71377 with respect to the translational start site, that does not create or delete any restriction site, but abolishes the consensus sequence for binding of transcription factor SP-1.25 It was reported that the wild-type allele G has a frequency of 0.87 in normal Caucasian population, whereas allele A has a frequency of 0.13.