FCRL, a novel member of the leukocyte Fc receptor family possesses unique structural features.
A novel conserved member of the leukocyte Fc receptor (FcR) family was identified in human and mouse. The presumably secreted protein, designated FCRL (FcR-like) is comprised of four domains. The three N-terminal domains are related to the extracellular region of FcgammaRI, with the second (35-37% residue identity) and the third (46-52%) domains showing highest similarity. The C-terminal domain is a unique sequence enriched with proline residues. In humans, alternative transcripts for six FCRL isoforms were revealed. Spleen and tonsils were found to be the major sources of FCRL mRNA in human tissues. Western blotting of tonsil cell lysate using FCRL-specific antibodies recognized a 44-kDa protein produced as a monomer containing free sulfhydryl groups. The monomer, however, was able to form disulfide-linked homo-oligomer upon oxidation. In COS-7 cells transiently transfected with two human FCRL isoforms, both resided intracellularly. Immunohistochemical staining of tonsil sections demonstrated the FCRL expression in germinal centers, suggesting that the protein may be implicated in germinal center-specific stages of B cell development. The phylogenetic analysis of the FCRL relationships with the leukocyte FcR supports a view that the three-domain structure was primordial in the evolution of the family.
Mechetina
Ludmila V
LV
Institute of Cytology and Genetics, Novosibirsk, Russia.
Najakshin
Alexander M
AM
Volkova
Olga Y
OY
Guselnikov
Sergei V
SV
Faizulin
Rafik Z
RZ
Alabyev
Boris Y
BY
Chikaev
Nikolai A
NA
Vinogradova
Maria S
MS
Taranin
Alexander V
AV
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D019556:COS Cells; D002522:Chlorocebus aethiops; D018076:DNA, Complementary; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D014066:Palatine Tonsil / Q000378:metabolism; D010802:Phylogeny; D020033:Protein Isoforms / Q000737:chemistry / Q000145:classification / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary; D011817:Rabbits; D011961:Receptors, Fc / Q000737:chemistry* / Q000145:classification / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014018:Tissue Distribution
D018076:DNA, Complementary; C452186:FCRLA protein, human; D020033:Protein Isoforms; D011961:Receptors, Fc