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BIOC212 > Cell interaction > Flashcards

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
Q

Integrin activation – outside in is regulated by

A

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
Q

Integrin activation – inside out is regulated by

A

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
Q

Integrins affinity for their ligands

A

Integrins have low to moderate affinity for their ligands

28
Q

clustering

A

Ligand binding promotes lateral diffusion and redistribution of integrins to focal complexes

29
Q

soluble fibronectin dimers conformation?

is mediated by ?

A

-soluble fibronectin dimers have a compact conformation mediated by intramolecular interactions

30
Q

Collagens are composed of

A

three polypeptide chains
- a-chains
46 collagen genes - 28 collagen types

31
Q

What do collagens form? how can they exist?

A

triple helix

Exist as homotrimers or heterotrimers

32
Q

structure of collagen alpha chain

A

GLY-X-Y

  • X proline
  • Y often hydroproline
  • G glycine
33
Q

What is at the center of the triple helix?

A

Glycine is every third reside, smallest aa

34
Q

Collagen precursors

A

prepeptides and proalpha chains

35
Q

How do collagen precursors become collagen (2)

A

hydroxylation, glycosylation

36
Q

Glycosylation

A

monosaccharide galactose or disaccharide glycosylgalactose

37
Q

Role of propeptide

A

guide intracellular formation of the triple-stranded collagen molecules

prevent intracellular formation of large collagen fibrils

38
Q

When is the assembly of collagen occur?

A

only after secretion

39
Q

Extracellular procollagen processing

A
  • Only fibrillar collagens
    uses
    Procollagen N-proteinase Procollagen C-proteinase
    and is zinc-dependent
40
Q

Procollagen N-proteinase

A

ADAMTS-2-3-14

41
Q

Procollagen C-proteinase

A

Tolloid Family

42
Q

Both Procollagen C-proteinase and Procollagen N-proteinase are .. binding ..

A

zinc binding metalloproteases

43
Q

removal of the C-propeptide

A

decreases critical concentration for self-assembly

44
Q

Structure of a generic collagen fibril

A
  • 300 nm in length

1000 amino acid residues

45
Q

D period of collagen fibril

A

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
Q

.. molecules form a microfibril in a … fashion

A

5 molecules form a microfibril in a concentric fashion

47
Q

Formation of Fibrillar Collagens is an

A

entropy driven self-assembly process

48
Q

After secretion in ER lumen what happens to prolines and lysines?

A

hydroxylated

49
Q

prolyl hydroxylase have a cofactor of

A

vitamin C

50
Q

prolyl hydroxylase characteristics

A

requires Fe+ and vitamin C
membrane bound
dioxygenase
inactivates the enzyme in absence of substrate

51
Q

Scurvy

what is it? due to ?

A

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
Q

Cross-links in Collagens is due to

A

Lysyl Oxidase

53
Q

Lysyl Oxidase are dependent on

A

copper-dependent

54
Q

Lysyl Oxidase converts

A

some lysines and hydroxylsines to allysines and hydroxyl-allysines

covalent cross-links

55
Q

Prolyl hydroxylase adds .. to … in .. dependent on ..

A

Prolyl hydroxylase - adds hydroxyl group to some prolines. (ER/Golgi) (Vitamin C and Fe2+)

56
Q

Lysyl hydroxylase adds .. to … in .. dependent on ..

A

Lysyl hydroxylase - adds hydroxyl group to some lysines. (ER/Golgi) (Vitamin C and Fe2+)

57
Q

N- and C-Propeptidases cleaves .. to … in .. dependent on ..

A

N- and C-Propeptidases - cleave collagen propeptides outside the cells. (Extracellular) (Zn2+)

58
Q

Lysyl oxidase converts .. to … in .. dependent on ..

A

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
Q

Collagen Defects syndrome

A

Ehlers-Danlos Syndrome

60
Q

Types of Ehlers-Danlos Syndrome

A 
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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