Polysialic acid is an unusual posttranslational modification that occurs on neural cell adhesion molecules (NCAM).
This vast range causes differences in the polySia's ability to adhere different cells, assist in cellular migration, synapse formation, and regulate adhesion in nerve cells by modeling and formating them.
This polySia linkage is found in proteins such as NCAM, E-selectin ligand 1 (ESL-1), C–C chemokine receptor type 7 (CCR7), synaptic cell adhesion molecule-1 (SynCAM-1), neuropilin-2 (NRP-2), the CD36 scavenger receptor found in the milk of humans, and the α-subunit of the voltage-sensitive sodium channel.
[2] The synthesis of polySia is enzymatically formed by α2,8-sialyltransferase (ST8Sia) in a Type II transmembrane protein located on the Golgi Apparatus membrane.
[1] E. coli is an encapsulated, gram-negative bacteria in which Barry and Goebel studied, pinpointing polySia, which they called colominic acid.
[1] Due to the capsule containing polySia, many scientists have tried to generate vaccines for these specific bacteria, notoriously difficult to target.
Another issue is that polySia found in bacteria does not produce a solid or consistent immune response.
It is known that there are many different structures of polySia and these were difficult to recognize and detect until this fluorescent labeling, making it very advantageous.
The major examples include membranes, neuron signaling, the immune system, neutrophil extracellular trap formation, and macrophage and microglia function.
Hydration and charge were noted before and after removing polySia from a membrane and a 25% decrease in the distance between cells was observed.
polySia does not only have repulsive interactions, as there are positive charge molecules located in lipid rafts, such as NCAM.
However, it is known that polySia is in regulatory functions in the immune system leading to protection from invaders and response to damaged tissue.
[2] polySia is involved in NETosis which is a reactionary function of the body in the presence of foreign invaders.