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SIGLEC5 (sialic acid binding Ig-like lectin 5 )

Certainty Style Key
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True   Likely   Speculative
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Human Uniqueness Compared to "Great Apes": 
Likely Difference
MOCA Domain: 
Genetics
MOCA Topic Authors: 
Ajit Varki

Siglec-5 is a sialic acid-recognizing inhibitory receptor found on certain immune cells types that is undergoing concerted evolution with the gene for Siglec-14 (an activatory receptor) via ongoing gene conversion of exons encoding amino-terminal V-set lg-like domains.  The result is that the two molecules have similar binding properties for sialic acids. However surprisingly, a critical arginine residue required for sialic acid recognition has been mutated in the corresponding molecules from the chimpanzee, gorilla and orangutan. It appears that this may be the ancestral condition, and that the human molecules have restored the arginine residue required for sialic acid recognition. It is unclear what the evolutionary significance of this adjustment is, and further studies are needed. It is interesting to note that a human-specific pathogen called Group B streptococcus can express a protein that ligates Siglec-5 and send a negative inhibitory signal to white blood cells

 

Type of Human-Specific Changes in SIGLEC5:

Functional Differences in protein coding sequences

Gene Conversion

Concerted Evolution

 

 

 

 

 

 

 

 

Related MOCA Topics
Related Topics:
TitleCertainty
HIV Progression to AIDS Speculative
Siglec Expression on T Cells True
SIGLEC14 (sialic acid binding Ig-like lectin 14)True
T Cell Reactivity Likely
Referenced By:
TitleCertainty
HIV Progression to AIDS Speculative
SIGLEC True
Siglec Expression on T Cells Likely
SIGLEC14 (sialic acid binding Ig-like lectin 14)True
T Cell Reactivity Likely
Viral Hepatitis Complications Speculative
Timing

Timing of Appearance of the Difference in the Hominin Lineage.

For this entry assume that

  • the common ancestor of humans and old world monkeys was 25000 thousand (25 million) years ago
  • the common ancestor of humans and chimpanzees was 6000 thousand (6 million) years ago
  • the emergence of the genus Homo was 2000 thousand (2 million) years ago
  • the common ancestor of modern humans was 100 thousand years ago

 

Definite Appearance: 
100 Thousand Years
References: 

Angata, T., Hayakawa, T., Yamanaka, M., Varki, A., and Nakamura, M. 2006. Discovery of Siglec-14, a novel sialic acid receptor undergoing concerted evolution with Siglec-5 in primates. FASEB J. 20:1964-1973.
Carlin, A.F., Chang, Y.C., Areschoug, T., Lindahl, G., Hurtado-Ziola, N., King, C.C., Varki, A., and Nizet, V. 2009. Group B Streptococcus suppression of phagocyte functions by protein-mediated engagement of human Siglec-5. J Exp Med. 206:1691-1699.