The cell adhesion molecule CEACAM1-L is a substrate of caspase-3-mediated cleavage in apoptotic mouse intestinal cells.
The CEACAM1 cell adhesion molecule is a member of the carcinoembryonic antigen family. In the mouse, four distinct isoforms are generated by alternative splicing. These encode either two or four immunoglobulin domains linked through a transmembrane domain to a cytoplasmic domain that encompasses either a short 10-amino acid tail or a longer one of 73 amino acids. Inclusion of exon 7, well conserved in evolution, generates the long cytoplasmic domain. A potential caspase recognition site in mouse, rat, and human CEACAM1-L also becomes available within the peptide encoded by exon 7. We used CEACAM1-L-transfected mouse colon carcinoma CT51 cells treated with three different apoptotic agents to study its fate during cell death. We found that CEACAM1-L is cleaved resulting in rapid degradation of most of its 8-kDa cytoplasmic domain. Caspase-mediated cleavage was demonstrated using purified recombinant caspases. The long cytoplasmic domain was cleaved specifically by caspase-3 in vitro but not by caspase-7 or -8. Moreover cleavage of CEACAM1-L in apoptotic cells was blocked by addition of a selective caspase-3 inhibitor to the cultures. Using point and deletion mutants, the conserved DQRD motif in the membrane-proximal cytoplasmic domain was identified as a caspase cleavage site. We also show that once CEACAM1-L is caspase-cleaved it becomes a stronger adhesion molecule than both the shorter and the longer expressing isoforms.
Houde
Caroline
C
McGill Cancer Centre, McGill University, Montreal, Quebec H3G 1Y6, Canada.
Roy
Sophie
S
Leung
Nelly
N
Nicholson
Donald W
DW
Beauchemin
Nicole
N
D000595:Amino Acid Sequence; D000818:Animals; D015703:Antigens, CD / Q000737:chemistry / Q000378:metabolism*; D000943:Antigens, Differentiation / Q000737:chemistry / Q000378:metabolism*; D017209:Apoptosis / Q000502:physiology*; D002272:Carcinoembryonic Antigen; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism*; D015815:Cell Adhesion Molecules; D002460:Cell Line; D003110:Colonic Neoplasms / Q000378:metabolism / Q000473:pathology; D007413:Intestinal Mucosa / Q000378:metabolism*; D007422:Intestines / Q000473:pathology*; D051379:Mice; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000378:metabolism; D020033:Protein Isoforms / Q000737:chemistry / Q000378:metabolism; D013379:Substrate Specificity
D015703:Antigens, CD; D000943:Antigens, Differentiation; C069847:CD66 antigens; D002272:Carcinoembryonic Antigen; C486183:Ceacam1 protein, mouse; D015815:Cell Adhesion Molecules; D010446:Peptide Fragments; D020033:Protein Isoforms; C505407:CASP3 protein, human; C505409:Casp3 protein, mouse; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases