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BIOC2301 > Membranes and Cell Signalling Ponnambalam > Flashcards

Membranes and Cell Signalling Ponnambalam Flashcards

1
Q

What are lipids central role?

A

Biological membrane component, also serve as energy stores and many intermolecular signalling events involve lipid molecules

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2
Q

What does phosphoinositide lipid signalling mediate?

A

The effects of a variety of hormones, signalling pathways, membrane protein activity (ion channels), lipid transfer protein activity, sculpting or modulating vesicle fusion and fission in membrane trafficking.

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3
Q

Describe phosphoinositide lipid signalling?

A

Signal transduction via a phosphoinositide pathway generates the second messenger inositoltriphosophate. This triggers calcium ion release or a diacyl glycerol which activates protein kinase C.

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4
Q

What do phosphoinositides bind?

A

Pleckstrin homology domain

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5
Q

How are phosphoinositides localised to different intracellular locations?

A

PI(3)P- endosomes
PI(4)P- Golgi
PI(4,5)P2 and PI(4,5,3)P3- plasma membrane.

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6
Q

What does phospholipase C family regulate?

A

Signal Transduction

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7
Q

How does phospholipase C work?

A

PH domain – binds PI lipids
C2 domain – binds membranes in the presence of calcium ions
SH2 domain – binds phosphotyrosine epitopes
SH3 domain – binds polyproline motifs
RasGEF – acts to promote GTP exchange and activation of Ras proto-oncogene
EF hands – binds calcium ions

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8
Q

What is protein kinase C family linked to?

A

Lipid metabolism.

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9
Q

How do protein kinase C work?

A

C1 domain – binds DAG lipid
C2 domain – binds membranes in the presence of calcium ions
C3 domain – binds ATP
C4 domain – binds substrate for phosphorylation by kinase d

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10
Q

What is the structure of phosphoinositides?

A

Variable head groups, 2x fatty acyl C18-20 chains, glycerol backbone, inositol sugar attached to terminal glycerol carbon

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11
Q

How many types of phosphatidylinositol 3-kinase are there?

A

4: 1A, 1B, 2 and 3.

All have regulatory subunits.

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12
Q

How are the Phosphatidylinositol 3-kinase different?

A

1A are localised to membranes and endosomes
2 are localised to Golgi and secretory pathway
3 are localised to Golgi and endosomes.

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13
Q

What are sphingolipids?

A

Second messengers.

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14
Q

What are sphingolipids biological effects?

A

Regulates cell stress, membrane trafficking, cell survival, apoptosis, phagocytosis and macrophage degradation.

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15
Q

What activate GPCR?

A

Lipid derived compounds: eg. Prostaglandins and leukotrines

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16
Q

What are nuclear activators?

A

Lipid derived compounds eg. Steroid hormones, retinoic acid PPAR family.

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17
Q

How many protein kinases does the human genome encode?

A

~518
90 tyrosine kinases
58 receptor tyrosine kinases in 20 subfamilies
32 cytoplasmic tyrosine kinases

18
Q

What are the roles of tyrosine phosphorylation?

A

Growth factor signalling and oncogenesis, cell adhesion, spreading, migration and shape, cell cycle control and development, gene regulation.

19
Q

What domains do rector tyrosine kinases have?

A

Extracellular, transmembrane, juxtamembrane, tyrosine kinase and c-terminal tail.

20
Q

What do receptor tyrosine kinase domains do?

A

Extracellular for ligand binding, transmembrane membrane anchor, juxtamembrane for negative regulation, tyrosine kinase for catalysis and c-terminal tail for signal regulation.

21
Q

What does RTK activation lead to?

A

Protein recruitment and signalling.
Promotes oligomerisation and autophosphorylation, alter gene expression, cause signalling platform assembly, can lead to Ras and MAPK activation.

22
Q

What are G-proteins?

A

GTP-hydrolyses [On/off] binary switches.

23
Q

What are G-proteins involved in?

A

Cyclic AMP signalling, MAP kinase signalling, PLD signalling, Redox signalling, cytoskeletal remodelling, ion channel modulation.

24
Q

What is a a G-protein complex?

A

Recruited by GPCRs contains a 7 transmembrane GPCR, a heteromeric G-protein and a downstream signalling proteins and enzymes.

25
Q

What is a heteromeric G-protein?

A

Galphabetagamma

26
Q

How does the G-protein complex work?

A

Inactive GPCR bind G.GDP.
The ligand binds triggering GDP exchange for GTP in the Galpha subunit.
Activated G.GTP dissociates to free alpha.GTP and beta gamma.
Alpha.GTP and beta gamma can activate different target proteins.

27
Q

What do complex molecular scaffolds do?

A

Increase signalling efficiency and enhance spatial organisation of signalling.
Do this by increasing the local concentration of signalling proteins and localising them.

28
Q

Name some families of G-proteins?

A

Ras, Ran, Rab, Rho, Sar etc.

29
Q

What are G-proteins similar to?

A

The alpha subunit of GPCRs. Both prenylated and similar size.

30
Q

What are GEFs?

A

Guanine nucleotide exchange factors, they promote activation

31
Q

What are GAPs?

A

GTPase activating proteins, they accelerate hydrolysis and deactivation.

32
Q

What are GDIs?

A

GDP dissociation inhibitors, they slow spontaneous nucleotide exchange.

33
Q

What is Ras?

A

Small, ~200 residue, monomeric G-protein and protoncogene.

34
Q

What does a oncogenic mutation in Ras cause?

A

A permanent GTP-bound on state, which leads to proliferation, death or differentiation.

35
Q

What does Ras link?

A

Cell surface receptors activation to MAPK pathways, also coupled to growth factor and RTK, EGFR and TrKA (nerve factor receptor)

36
Q

What can Ras avtivation lead to?

A

Activation of Raf protein kinases and Rac activation

37
Q

What are Rab GTPases?

A

Ras-like GTPases that regulate membrane trafficking between intracellular compartments by regulating vesicle fusion and docking.

38
Q

What regulates Rab-GTPases?

A

GEFs, GAPs and act in concert with SNAREs

39
Q

What do Rho-like GTPase superfamily regulate?

A

Intracellular signalling, cell shape and migration.

40
Q

What are Rho-like GTPases important in?

A

Pathogenic infection.

41
Q

What are Rho-like GTPases regulated by?

A

Adhesion linked tyrosine kinases: focal adhesion kinases (FAKs) activation stimulates GDP/GTP exchange triggering changes in actin cytoskeleton.

42
Q

What are lipids?

A

The fourth major group of molecules in all cells

BIOC2301 (15 decks)

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