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MBOD Week 15 > Functions Of Secreted Glycoproteins > Flashcards

Functions Of Secreted Glycoproteins Flashcards

1
Q

T or F: most extracellular Proteins are Glycoproteins

A

True

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2
Q

What are N-linked sugars attached to?

A

Asparagine (N)

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3
Q

What are O-linked sugars attached to?

A

Serine, Threonine, Hydroxylysine

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4
Q

T or F: Cells that are present in the wrong places in the body will likely die

A

True, e.g. liver cells can’t live in the skin

  • This is due to lack of the appropriate receptors on the liver cell to get the stuff it needs from the environment
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5
Q

How does ebola initiate interactions with endothelial cells?

  • Why not other cells?
  • How does proliferation continue?
A
  1. Finds a coat glycoprotein on endothelial Cells
  2. Cell becomes infected and dies (Hemorrage)
  3. Soluble Glycoprotein blocks early general assault and inflammation (blocks neutrophils)
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6
Q

What is the difference between a glycoprotein and a proteoglycan?

**Note: that proteoglycans are just a subset of glycoprotein

A

Glycoprotein:
low amount of Carbs attached

Proteoglycan:
More sugar and GLYCOSAMINOGLYCAN chains (GAGs) are attached

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7
Q

What is a glycosaminoglycan (GAG)?

A
  • Repeated polysaccharide with alternating amino sugars and acidic sugars
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8
Q

What is one important exception to the fact that all glycoproteins are extracellular and most extracellular proteins are glycosylated?

A

Albumin - abundant Serum Transport Protein

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9
Q

What are lectins?

A

Carbodydrate binding proteins for:

  • cell attachment
  • immune response
  • lung surfactant
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10
Q

What glycoprotein is involved in copper binding and transport?

A

Ceruloplasmin

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11
Q

What is N-acetyl-glucosamine?

A

Glucose Ring Derivatized at the 2-position

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12
Q

T or F: Sialic acid is aka as N-Acetylneuraminate (NANA)

A

True

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13
Q

What is glycosylation?

A
  • The process of transferring an oligosaccharide to a protein
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14
Q 
******************************
N-linked Glycosylation:
- Where does it occur?
- When does it happen
- How does it happen?
A

Where:
- Starts in Rough ER and is finished in the Golgi

When:
- AS the Polypeptide is being synthesized

How:
- Preassembled oligosaccharide is transferred to the appropriate Asparagine

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15
Q

What sequence gives consensus for N-linked glycosylation?

A

Asn-X-Ser/Thr

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16
Q

T or F: from yeast to man, the preassembled oligosaccharide is always the same

A

True

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17
Q

Dolichol:

  • What is it?
  • Bond Type?
  • Predominant Sugar?
A
  • Dolichol is a carrier of the universal pre-assembled oligosaccharide
  • Linked to the Oligosaccharide via a diphosphate bond
  • Mannose and Glucose are Predominant in this molecule
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18
Q

When can a preassembled oligosaccharide be transferred from Dolichol to another protein?
- Bonds Broken and Formed?

A
  • Transferred to Asn-X-Ser/Thr

- Disulfate bond to Dolichol is broken, and N-glycosyl bond is formed

19
Q

Where does Dolichol transfer the oligosaccharide to proteins, where is Dolichol located?

A
  • Dolichol present in RER membrane transfers Oligosaccharide to and Asn In the RER LUMEN
20
Q

If all N-glycolsylated proteins start off with the same oligosaccharide attached how do they differentiate?
- where does this occur

A

Remove:

  • Glucoses
  • Mannoses

Add:

  • Galactose
  • Sialic Acid
  • Fructose

**Occurs as the protein passes from the ER to the Golgi

21
Q

T or F: O-linked glycosylation occurs one sugar at a time

A

True

22
Q

What adds glycosyl groups in O-linked glycosylation?

- substrate for these enzymes?

A
  • Glycosyl Transferases Used

- Sugar Nucleotide (e.g. UDP-Gal) are used

23
Q

What is the job of fibronectin?

A
  • Binds Both Cells and Extracellular Matrix Molecules (e.g. Collagen)
24
Q

What does the structure of fibronectin consist of?

A
  • Dimer (2 similar subunits)

- Joined by Disulfide Bond at C-terminal

25
Q

How many many Fibronectin Genes are there?

- How many isoforms

A

1 Gene

3 Isoforms

**Alternate splicing allows for this

26
Q

What modules are in Fibronectin?

- Function

A
  • Globular Polypeptides that are like beads on a string
  • Each “Bead” has a different function

Module Functions:

  1. Cell (Integrin) Binding
  2. Collagen Binding
  3. Heparan Sulfate Binding
  4. Fibrin Binding
27
Q

What is Laminin?

A
  • Similar to Fibronectin (binds different things together) - formed in basal lamina

(glycoprotein)

28
Q

What is aggrecan?

A
  • Glycoprotein that forms a shock absorbing aggregate
29
Q

What are 3 main functions of glycoproteins?

A
  1. Comprise Recognition Signals
  2. Intracellular Trafficking
  3. Building Protein-Protein Interactions for CT scaffolding
30
Q

What happens if glycoproteins loose too many of their glycosylations?

A
  • They loose their water solubility and fallout of solution

- PROTEASES then degrade these

31
Q

T or F: glycosylation protects glycoproteins from degradation

A

True

32
Q

What happens if 2 of the 10 sialic acids are removed from the glycosylated portion of ceruloplasmin?

A

Half Life Deceases by 700x

33
Q

What is Beta-glycan?

A

Transmembrane glycoprotein:

- Hormone Receptor for transforming growth factor-beta

34
Q

Integrins:

  • What do they do?
  • How do they do it?
A

What they do:
Transmembrane Glycoproteins that mediate Cell-matrix binding

How:
- Binding ECM protein to allow cells to grip a given surface

35
Q

T or F: most cells must be anchored to ECM by integrin to be viable

A

True, keeping the cell bound to ECM keeps it in contact with cell survival signals

36
Q

What is a cadherin?

A

Ca2+ dependent Adhesion Molecule

37
Q

If you chop up liver and retina cells and mix them what will happen an why?

A
  • Retina Cells will aggregate with each other and Liver cells will aggregate with other liver cells
  • This happens because of specific Cell-Cell interactions that only occur between cells of the same type
38
Q

What role do glycoproteins play in fertilization of an egg by sperm?

A
  1. Capacitation - sperm alters is membrane glycoprotein and gal-transferase recognizes egg
  2. Zona Pellucida (glycoproteins) act as a sperm receptor
39
Q

What role do glycoproteins play in the extravasation of white cells?

A
  1. Selectins present on endothelial cells and bring white cells to a rolling stop
  2. Integrins then grab onto the cell tighter and it is pulled through the endothelium (extravasation)

**Leads to an inflammatory Response

40
Q

Why would you want to inhibit selectin that is used in extravasation?

A
  • Extravasation leads to inflammation
  • After a heart attack inflammation is bad and can cause additional damage

**No selectin, then no extravasation

41
Q

What is needed to target a protein to a Lysosome?

A
  • Glycoprotein with a PHOSPHOMANNOSE
42
Q

What happens if PHOSPHOMANNOSE can’t be added to a protein?

A
  • It will not get targeted to lysosome
  • This can cause accumulation of macromolecules in Lysosome
    (e. g I-Cell disease and ß-glucuronidase)
43
Q

T or F: sugars in glycoproteins are covalently attached

A

True

MBOD Week 15 (7 decks)

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