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Cell interaction Flashcards

1
Q

Fuction of selectins

Weak adhesion and rolling vs strong adhesion and emigration

A

Weak adhesion and rolling
- selectin-dependent
strong adhesion and emigration
- integrin dependent

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2
Q

Inflammation site

A

Endothelial cells express selectins,

oligosaccharides are located on lymphocytes

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3
Q

N-CAM

A

Neural cell adhesion molecules

fine tuning of interactions during development and regeneration

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4
Q

I-CAM

A

Intercellular adhesion molecules (I-CAM)

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5
Q

V-CAM

A

Vascular cell adhesion molecules (V-CAM)

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6
Q

Are cadherins and ig-like CAMs frequently expressed

A

yes coexpression often

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7
Q

integrins in procaryotes, plants or fungi

A

no

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8
Q

Caenorhabditis elegans integrins

A

two alpha subunits and one

beta subunit => form two integrins

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9
Q

vertebrates integrins

A

18 a subunits

and 8 b subunits

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10
Q

Integrins participate in (3)

A
  • Cell-matrix adhesion
  • Cell-cell adhesion
  • Cell aggregation
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11
Q

Most integrins: connected via

A

intracellular anchor proteins to

actin (except: a6b4)

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12
Q

Integrin-Binding Sequences (on ECM proteins)

A

Involves frequently either D (Asp, aspartic acid) or E (Glu, glutamic acid) residue

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13
Q

RGD sequences

A

Arginine-Glycine-Aspartic acid

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14
Q

Collagen receptors

A

recognize ECM molecules

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15
Q

Leukocyte-specific receptors

A

recognize IG superfamily counter receptors

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16
Q

Integrin ligands often contain

… sites for receptor binding

A

accessory or ‘synergy

sites

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17
Q

Disintegrins can come from what animal

A

Large group of snake (viper) venom proteins containing a number of cysteine residues and RGD sequence

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18
Q

Disintegrins are rich with

A

RGB

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19
Q

What do Disintegrins do?

A

block the function of some integrins protein

Competitive inhibitor for integrin-fibrinin interactions and block blood coagulation

inhibitors of angionesis (blood vessel formation)

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20
Q

αIIbβ3 integrin mediates

A

blood platelet aggregation via binding to fibrinogen

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21
Q

integrin activation occurs via

A

exposure to Col IV or Thrombin (outside blood vessels)

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22
Q

Some integrins (α/β dimers) are

where are they

A

not constitutively active

– they are often on
the cell surface in inactive, non-ligand binding state

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23
Q

Activation can occur via (2)

A

extracellular ligand binding- outside-in” activation

Activation can occur from within the cell via the integrin cytoplasmic tail

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24
Q

Integrin activation is important for

A 
cell aggregation (adhesion of circulating cells [platelets] to   soluble matrix)
  cell-cell adhesion (leukocytes and inflammation)
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25
Integrin activation – outside in is regulated by
extracellular ligand: binding to the bent inactive conformation (weak interaction) conformational change: straightening of alpha and beta chains ligand will bind stronger conformational change: separation of the cytoplasmic domains
26
Integrin activation – inside out is regulated by
seperation of the cytoplasmic domains is accompanied by conformational changes in them, allowing binding of the cytoplasmic proteins and signalling separation of the cytoplasmic domains through talin and other activators would activated the head for ligand binding
27
Integrins affinity for their ligands
Integrins have low to moderate affinity for their ligands
28
clustering
Ligand binding promotes lateral diffusion and redistribution of integrins to focal complexes
29
soluble fibronectin dimers conformation? | is mediated by ?
-soluble fibronectin dimers have a compact conformation mediated by intramolecular interactions
30
Collagens are composed of
three polypeptide chains - a-chains 46 collagen genes - 28 collagen types
31
What do collagens form? how can they exist?
triple helix | Exist as homotrimers or heterotrimers
32
structure of collagen alpha chain
GLY-X-Y - X proline - Y often hydroproline - G glycine
33
What is at the center of the triple helix?
Glycine is every third reside, smallest aa
34
Collagen precursors
prepeptides and proalpha chains
35
How do collagen precursors become collagen (2)
hydroxylation, glycosylation
36
Glycosylation
monosaccharide galactose or disaccharide glycosylgalactose
37
Role of propeptide
guide intracellular formation of the triple-stranded collagen molecules prevent intracellular formation of large collagen fibrils
38
When is the assembly of collagen occur?
only after secretion
39
Extracellular procollagen processing
- Only fibrillar collagens uses Procollagen N-proteinase Procollagen C-proteinase and is zinc-dependent
40
Procollagen N-proteinase
ADAMTS-2-3-14
41
Procollagen C-proteinase
Tolloid Family
42
Both Procollagen C-proteinase and Procollagen N-proteinase are .. binding ..
zinc binding metalloproteases
43
removal of the C-propeptide
decreases critical concentration for self-assembly
44
Structure of a generic collagen fibril
- 300 nm in length | 1000 amino acid residues
45
D period of collagen fibril
length of stagger between adjacent molecules - D-periodic collagen fibril on the bottom with characteristic alternating light/dark pattern representing the gap and overlap fibril.
46
.. molecules form a microfibril in a ... fashion
5 molecules form a microfibril in a concentric fashion
47
Formation of Fibrillar Collagens is an
entropy driven self-assembly process
48
After secretion in ER lumen what happens to prolines and lysines?
hydroxylated
49
prolyl hydroxylase have a cofactor of
vitamin C
50
prolyl hydroxylase characteristics
requires Fe+ and vitamin C membrane bound dioxygenase inactivates the enzyme in absence of substrate
51
Scurvy | what is it? due to ?
defective collagen production rupturting of blood vessels defective wound healing bleeding gums Due to lack of Vitamin C (ascorbic acid) – a cofactor for prolyl and lysyl hydroxylase
52
Cross-links in Collagens is due to
Lysyl Oxidase
53
Lysyl Oxidase are dependent on
copper-dependent
54
Lysyl Oxidase converts
some lysines and hydroxylsines to allysines and hydroxyl-allysines covalent cross-links
55
Prolyl hydroxylase adds .. to ... in .. dependent on ..
Prolyl hydroxylase - adds hydroxyl group to some prolines. (ER/Golgi) (Vitamin C and Fe2+)
56
Lysyl hydroxylase adds .. to ... in .. dependent on ..
Lysyl hydroxylase - adds hydroxyl group to some lysines. (ER/Golgi) (Vitamin C and Fe2+)
57
N- and C-Propeptidases cleaves .. to ... in .. dependent on ..
N- and C-Propeptidases - cleave collagen propeptides outside the cells. (Extracellular) (Zn2+)
58
Lysyl oxidase converts .. to ... in .. dependent on ..
Lysyl oxidase - converts some lysines and hydroxylysines to allysines and hydroxy-allysines. These reactive aldehydes react with free (hydroxy)lysines to form covalent cross-links. (Extracellular) (Cu2+)
59
Collagen Defects syndrome
Ehlers-Danlos Syndrome
60
Types of Ehlers-Danlos Syndrome
``` Classical type (Collagen type V defect, a1 chain) ``` ``` Hypermobility type (tenascin XB defect) (collagen fibrillogenesis) ``` ``` Vascular type (Collagen type III) ``` ``` Kyphoscoliosis type (Lysyl hydroxylase-1 deficiency) ``` ``` Arthrochalasia type (Collagen type I) ``` Dermatosparaxis type (ADAMTS-2 defect)

BIOC212 (7 decks)

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