glycoimmunology 1

Question 1

what is glycocalyx

Answer 1

carbohydrate that coats the cell

Question 2

functions of the glycocalyx

Answer 2

cell-cell communications
interactions with the extracellular matrix
protections from and susceptibility to pathogens
modulation of immune response

Question 3

glycosylation

Answer 3

a post translational modification
addition of a sugar molecule
1-2% of genome devoted to glycosylation
combinatorial linkage, position and branching

Question 4

classes of eukaryotic glycans

Answer 4

glycoprotein glycans - n linked or o linked
glycolipids
proteoglycans
gpi-anchors
0-glcnac glycosylation of cytoplasmic and nuclear proteins

Question 5

processing n linked glycans

Answer 5

protein synthesised within the ER
section of the protein that is meant to be extracellular is found in lumen
flipase enzymes flip the sugar insdie
highly conserved
last step occurs in the golgi - mannosidase removes mannose\glcnac transferases start to build glycans back up

Question 6

synthesis of o linked glycans

Answer 6

occur sin the golgi
no addition of o linked in er
enzymes in golgi build up glycans in a stepwise manner

Question 7

general aspects of the gylcan strucutre

Answer 7

core sequence - common to all n glycans
extension seq - common to all cells may vary between glycans
terminal seq - cell type specific expression

Question 8

how are glycans arranged

Answer 8

canopy
comparisons between terminals, core and extensions
organsied at cell surface

Question 9

what is glycomics

Answer 9

the study of the glycome

glycoproteome is a major subset of the proteome

Question 10

functions of glycans

Answer 10

structural - folding proteins, stability and solubility
functional - reg of interactions with other glycoprotiens
recognition - host lectins, pathogen lectins
complexity - reflects diff funcs above

Question 11

lectins expressed by pathogens

Answer 11

viruses, bacteria and proteozoa use lectins to attach to cells and mediate steps to host infection
bacterial lectins occur commonly in the form of elongated, submicroscopic, multisubunit protein appendages

Question 12

velcro analogy of lectins

Answer 12

binding of lectins to ogliosaccaride ligands is low affinity

stable binding requires multivalent interactions which leads to high avidity

Question 13

glycan array

Answer 13

ligand identification
isolates and synthesises sugars
incubate on an array with protein of interest
image array to find specificity of a protein

Question 14

collectins

Answer 14

c type lectins
mannose binding anf ficolins in plasma 
sugar binding region in head
high affinity binding to pathogens
collagen tail

Question 15

selectins

Answer 15

best characterised mammalian lectin
essential for leukocyte trafficking
important in inflammation
slow down leukocytes and tether them to the endothelium

Question 16

antobodies against p selectin

Answer 16

delays onset of pain crisis in sickle cell disease

p slectin on platlets contribute to these