Description of an elasmobranch TCR coreceptor: CD8α from Rhinobatos productus

Developmental and Comparative Immunology
By: , and 



Cell-mediated immunity plays an essential role for the control and eradication of intracellular pathogens. To learn more about the evolutionary origins of the first signal (Signal 1) for T-cell activation, we cloned CD8α from an elasmobranch, Rhinobatos productus. Similar to full-length CD8α cDNAs from other vertebrates, Rhpr-CD8α (1800 bp) encodes a 219 amino acid open reading frame composed of a signal peptide, an extracellular IgSF V domain and a stalk/hinge region followed by a well-conserved transmembrane domain and cytoplasmic tail. Overall, the mature Rhpr-CD8α protein (201 aa) displays ~30% amino acid identity with mammalian CD8α including absolute conservation of cysteine residues involved in the IgSf V domain fold and dimerization of CD8αα and CD8αβ. One prominent feature is the absence of the LCK association motif (CXC) that is needed for achieving signal 1 in tetrapods. Both elasmobranch and teleost CD8α protein sequences possess a similar but distinctly different motif (CXH) in the cytoplasmic tail. The overall genomic structure of CD8α has been conserved during the course of vertebrate evolution both for the number of exons and phase of splicing. Finally, quantitative RTPCR demonstrated that elasmobranch CD8α is expressed in lymphoid-rich tissues similar to CD8 in other vertebrates. The results from this study indicate the existence of CD8 prior to the emergence of the gnathostomes (>450 MYA) while providing evidence that the canonical LCK association motif in mammals is likely a derived characteristic of tetrapod CD8α, suggesting potential differences for T-cell education and activation in the various gnathostomes.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Description of an elasmobranch TCR coreceptor: CD8α from Rhinobatos productus
Series title Developmental and Comparative Immunology
DOI 10.1016/j.dci.2010.11.014
Volume 35
Issue 4
Year Published 2011
Language English
Publisher Elsevier
Contributing office(s) Western Fisheries Research Center
Description 9 p.
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Developmental and Comparative Immunology
First page 452
Last page 460
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