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Glycobiology Flashcards

1
Q

What are the three main components of glycobiology

A

Lectins Glycans and Glycoenzyems

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2
Q

What are glycans

A

Carbohydrates and sugars

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3
Q

What are lectins

A

Glycan binding protiens

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4
Q

What are glycan modifying enzymes

A

Glycotransferase and glycosidases

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5
Q

What are the central molecules of glycobiology

A

Glycans that are produced or modified by glycoenzymes and recognized by lectins

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6
Q

What is glycocalyx

A

Used to describe the carbohydrate rich zone on the cell surface

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7
Q

How can you recognize the glycocalyx zone

A

Using a variety of stains such as ruthenium red
Also its affinity for carbohydrate-binding protiens called lectins which can be labeled with a flourescent dye or another visible marker

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8
Q

What is glycocalyx made up of

A

Glycan chains of membrane glycoproteins and glycolipids and absorbed glycomolecules

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9
Q

What is the function of the glycocalyx

A

Protect cells against mechanical and chemic to keep foreign objects and other cells at a distance preventing undesirable protien-protein interacations

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10
Q

What else can membrane glycoproteins do

A

Involved in transmembrane signalling and intercellular communications

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11
Q

What does the glycocalyx represent

A

Glycans represent complex branched structures of different sizes that looks like trees

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12
Q

What does the different dimensions of the glycocalyx mean

A

That the role of the glycocalyx may be cell-speceific and be involved in regulation of different cellular responses

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13
Q

How many common monosaccharides are there

A

9

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14
Q

D-glucose can exist in how many forms and what are they

A

three different forms a linear and two different rings a pyranose and furanose

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15
Q

Which ring of D-glucose dominantes in biological systems

A

Pyranose

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16
Q

What are the two different forms of anomers

A

Anomers and steriosmers which include alpha and beta anomers depending on the positon of the hydroxol group at position one

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17
Q

What is it called when sugars differ only by the configuration around one carbon atom

A

Epimers D-manose and Dglacotse are epimers of D-glucose

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18
Q

What are protiens

A

Linear polymers containg up to several thousand amino acids linked by peptide bonds

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19
Q

What are nucleic acids

A

Linear polymers containt hundreds to millions of nucleotides by phosphodiester bonds

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20
Q

What are glycans

A

Linear or branched polymers or monsaccharides linked by glycosidic bonds

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21
Q

What is the glycosidic bond formed by

A

The anomeric carbon of one monosaccharide and a hydroxyl group of another

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22
Q

What is the difference between glycans and proteins and nucleic acids

A

The glycosidic bonds can be formed between individual monsaccharides

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23
Q

What is an example of different bonds between individual monosaccharides

A

Lactose has a different bond between glactose and glucose then glucose has with fructose as result complex branched structures are common

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24
Q

What is the linkage in N-linked glycans

A

GlcNAc B linked to the amide nitrogen of an asparagine residue in the seqeuce Asn-X-Ser or Asn-X-Thr where X is any amino acid expect proline or aspartic acid

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25
What is the first sugar of N-glycans attached
GlcNac
26
What is the linkage of glycans in O-linked
Attached to the OH group of either serine or theroine resuidues
27
What is the most common O-glycosidic attachment
Involves the disaccharide core B-glactosyl (1-3) a- N-acetylglactoasimne
28
What are less common O-linked glycans
Glactose, mannose and xylose
29
Can O-linked glycans vary in size
YES from a single sugar residue to the long chains of up to 1000 monosaccharides units in proteoglycans
30
What do all N-linked glycans contain
A common core pentassacharide structre attached to asparagine but differ in temrinal elborations that extend from this core
31
What is glycoproteins
Glycosylate protiens with covalently linked N-glycans and O-glycans glycoprotiens are assembled through the ER-golgi pathway
32
What is GPI
Anchored glycoprotiens contain a specific glycan bridge between lipid anchor and the C-terminus of a protien
33
What is EGF/TSR
Epidmerla growth factor and thrombospondin represent membrane protiens which are glycosylated with only short unbranched carbohydrate structures
34
What are proteoglycans
Are glycoconjugates that have one or more glycoasminoglycans covalently attached to core protien they are linear
35
What are glycosphingolipids
Consists of a glycan usually attached via glucose or glactose to the terminal OH group of the lipid molecule
36
What are lectins
Protien that specifically recognizes and binds to glycans without catalyzing a modification of the glycan carbohydrate binding proteins other than immunoglobins that no enzymatic
37
What are lectins
Highly specic to individual monosaccharides which can link to other sugars in a complex glycans
38
What domain does lectin have
Carbohydrate-recognition domain which is respobsible for binding glycans
39
What do lectins function as
Multimers which allows them to bind seceral glycan molecules at a time
40
What happens if you add them to cell suspension
Bind cell surface glycans and make bridges between cells inducing cell aggregation
41
How can cell aggregation be detected
Spectrophotometrically by mesauring the light transmission of cellular suspension as the suspension of aggregated cells transmits more light than the supesnion of indivudal cells
42
What happens if inhibitory sugard were added
No cell aggregation was observed blocks CRD of VAA and GlcNAc blocks the CRD of WGA
43
What are the four types of animal lectins
1. galectins - soluble glactose binding lectins 2. C-type lectins transmembrane proteins with Ca depedent glycan binding specificiy 3. P type lectins transmembrane proteisn with aset of immunoglobuin domains 4. I typed lectins - transmembraen proteins with a set of immunoglbuil domains
44
What are glactins
Animal lectins that preferntially recognize B-glactoside containing glycans Share significant sequence similarties in the CRD Soluble multifunctional protiens
45
What are the three subfamiles of galectins
Proto-type with one CRD Tandem-repeat type with two different CRDs Chimeric with one CRD linked to a non lectin N terminal domain
46
Why are galectins important
Both inside and outside the cell that perform different functions
47
48
49
What is the CRD structure | Beta sheets
Beta sandwich with two sheets formed by six beta strands on concave side and five on the convex side
49
What does the HL-60 differeninate into
Eosinophil like cells Neutrophil- like cells Macrophage like cells depending on the type of stimuli
50
How HL-60 cell line maintained
It is a suspension cell line Orignated froma a female patient with acute promyelocytic lukemia Expresses 6 gallectins
51
What different stressors were used in extracellular stress stimuli
Conventional cellular stress exopixa CoCl1 Tunicamycin for ER stress
52
What did the study include after glactein expression and adhesion charactersitics of HS-60
manose glactose and sialiac acid and GlvNAc residues are available on the cell surface for cell contancts. The glacteins didnt change the prefrence to the binding of lectins in stress but changed the expression of it
53
What are the four categories of galectin genes are recognize in the context of cellular stress responses
Stress inducible Stress repressed Stress reistant Undetectable
54
How can oxidative stress be induced
Menadione which creates superoxide radiacal
55
What do HL-60 overexpress in oxidative stress and what does it repre
NCF1 gene and HMOX1 and 1, 3 and 10 and 9 was downrefgulates biological signficance network remodeling in conjucation with cellular stress responses
56
What is glycosyltransferase
An enzyme that catalyze transfer of a sugar from a sugar nucleotide dononr to substrate these enzymes are responsible for the synthesis of most glycoproteins and other glycoconjugates
57
What are glycosidases
Enzymes that catalyze hyrdolysis of glycosidic bonds in glycans: endoglycosidases catalyze the cleavage of internal glycosidic linkage while exoglycosidases cleave a monosaccharide from the terminal end of a glycan
58
What is glycan-degrading enzymes
Type of glycosidases that destroy large pollysaccharides
59
What does OGT do
Catalyze the transfer of a GlcNAc sugar from the donor substrate UDP-GLcNAx
59
WHere does GlcNAc bind
Hydrozyl groups of serine and theronine residues
60
What is OGA
Cataylzes the hydrolysis of this sugar modification and removes O-GlcNAc
61
Where does O-GlcNAcylation happens
Inside of cells in cytoplasm nucleus and mitochondria
62
How is UDP-GlcNAC produced
Is an OGT substrate through the hexosamine biosynthetic pathways
63
What is the rate liminting enzyme in Hexosamine biosynthetic pathway
GFAT
64
What is the pathway of hexosamine
Fru-6P to GlcN-6P through GFAT GlcN-6P then produces UDP-GcNaC This can also be recycled through the salvage pathway which converts GlcNAc back into GlcNAc-6P that can be utilized by the pathway
65
What competes with GlcNAcylation
Competes with phosphorylation because both are types of posttranslational modification that target Ser/Ther
66
What complex induces phosphorylation
OGA and Kinase
67
What complex induces glycoprotien
OGT and phosphotase
68
Where is O-GlcNAcylated most common
Cytsol and Nucleus less in endosome and peroxisomes
69
Where are the most O-GlcNacylated protiens and lowest | Body parts
Most is in the brain and liver Least is bones saliva gall bladder and urine
70
What happens when there is elevated O-GlcNA | Disease
Contirbutes directly to glucose toxicity in diabetes and cancer
71
What does decreased O-GlcNacylation
Alzheimers disease and parkinsons disease tau protien carries O-GlcNAc residueds that compete with key phosphorylation residued and prevents it aggreations
72
What happens to global O-GlcNAc levels
They are elveated in response to cellular stress in all cases of they observed signficant increase in intensitniy of bands
73
How do you run the immunodot blot assay
Immobilize cellular protiens then incubate the membrane with primary and secondary antibodies Does not require protein elctrophoresis Intensinity of dot is proportional to the levels in cells
74
How is the efficnancy confirmed
Increasing or decreasing levels of O-GlcNaC in cells treated with OGT inhibitor and OGA inhibitos
75
What was the finding in cellular differentiation
Levels of O-GlcNAc significantly decrease in differentiated cells versus progenitor cells
76
What else can O-GlcNAc regulate
Protien traffcking and turnover they are less transportable, more stable and usually not secreted from cells
77
What do regulatory fuctions of glacteins depend on
Localization of glactins in cells O-GlcNAc promote intracellular accumulation and where low levels of O-GlcNAc promote galectin secretion can be applied to glactein 3 and 9
78
What is LGALS12 for
Highest RNA expression in adipose tissue, breast and bone marrow
79
What is LGALS16
Highest RNA expression in normal placenta retina and brain tissues
80
What is the hypothesis of cell culture models to study tissue specefic galectins
Increased when cells become more specalized and decreased in cancer might act as tumor supressers and used different cell lines
81
What is the N1 phenotype
Showed increased activity of LGALS12 gene and behaved in a way that fights tumors and promtoes inflammation
82
What is the N2 phenotype
Showed decreased activity of LGALS12 and behavied in a way that supports tumor growth and reduces inflammation
83
What happend with LGALS16
When cells were treated with 8-BR-cAMP that promtoes the cells to mature into trophoblast like cells LGALS216 activity increased significantly CGB confrimed this
84
What is the role of LGALS16 in trophoblastic differentiation of JEG-3 cells?
Using CRISPR/Cas9 to knock out (KO) the LGALS16 gene in JEG-3 cells, researchers showed that these KO cells had: Lower response to 8-Br-cAMP, as seen in reduced CGB expression (both gene and protein levels). No changes in growth rate when treated with 8-Br-cAMP, unlike control cells. Conclusion: LGALS16 is essential for trophoblastic differentiation of JEG-3 cells.

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