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Biomed 2 > Cell Bio - Intracellular signalling > Flashcards

Cell Bio - Intracellular signalling Flashcards

1
Q

what does FRET show

A

shows that proteins tethered to the lipid membrane interact more

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2
Q

what does FRET (fluorescent resonance energy transfer) dependant on

A

depends on the distance of the flurophores
must be within approx. 10 nm

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3
Q

what drives cell transformation

A

forced membrane localisation of PKB

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4
Q

concerning protein localisation at the membrane what are the phosphobinding motifs and what is the other type of binding motif

A

SH2
PTB
ubiquitin binding motif

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5
Q

what is AKAP interaction domain

A

interaction between a cytosolic and membrane bound protein

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6
Q

concerning lipid interaction motifs, what are the phosphoinositide interacting motifs

A

PH
FYVE
PX
PHD
lysine - arginine (K-R) rich patches

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7
Q

in terms of protein-membrane localisation, what are the mechanisms used to control lipid tether at the membrane

A

myristoylation
prenylation

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8
Q

single lipid tethers are often not stable enough, how is this problem rectified

A

lipid tether is compined with lipid interaction motifs to induce stable localisation

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9
Q

what is fatty acylation

A

mainly consists of the addition of myristic or palmitic fatty acids to a protein

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10
Q

how is myristate bound to the protein

A

bound to the N-terminal glycine residue via an amide bond
irreversible

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11
Q

what is step 1 in myristoylation

A

removal of the N-terminal methionine

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12
Q

step 2 of myristoylation

A

activation of myristic acid via CoA

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13
Q

step 3 of myristoylation

A

coupling of myristic acid to glycine

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14
Q

what is the role of myristoylation in apoptosis

A

1 - caspase mediated cleavage of Bid exposes a glycine
2 - Bid is myristoylated
3 - lipid tether induces insertion into mitochondrial membrane
4 - recruitment of BAK to the mitochondrial membrane
5 - cytochrome-C is released
6 - apoptosis downstream

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15
Q

to what does prenylation occur

A

to proteins containing a CAAX motif on their C-terminus

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16
Q

what is a CAAX motif and what does it generate

A

C - cystine residue, functions as isoprenoid attachment
A - signifies any aliphatic amino acid
X - any of several amino acids
generated a thioether linkage

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17
Q

how is prenylation initiated

A

by the attachment of farnesyl/geranylgeranyl to the cystine residue via farnesyltransferase or garenylgeranyltransferase

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18
Q

how can a prenylated protein be further processed

A

RAS-converting CAAX endopeptidase 1 (RCE1) which removes the -AAX residues

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19
Q

what is the function of isoprenylcysteine carboxylmethyltransferase (ICMT)

A

caps the carboxy group on the now C-terminal isoprenoid-modified cystine residue
using a methyl group

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20
Q

what is Kras4B targeted to and how

A

targeted to PM
via interactions with its polybasic region with phosphoinositides

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21
Q

how often is Ras mutated in human tumours and where

A

16%
mutation in codon 12,13 and 61

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22
Q

why do H and N Ras undergo prenylation and palmitoylation

A

to target them stably to the membrane

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23
Q

how does Kras get targeted stably to the membrane

A

only undergoes prenylation
uses PRB for stable association to the membrane

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24
Q

what is progeria syndrome such as Hutchinson-Gilford (HGPS) caused by

A

abnormal processing of the CAAX protein
prelamin A

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25
what can be used to treat HGPS
Ftase inhibitors
26
effects of adrenergic activation
Increase strength and heart rate Increased blood flow to muscle Increased systemic and cellular energy supply Increased skeletal muscle force decreased gut motility decreased peripheral blood flow
27
what releases norepinephrine
sympathetic nervous system post-ganglionic fibres
28
where do alpha-adrenoceptors occupy
smooth muscle cells
29
where do beta-adrenoceptors occupy
adipose tissue skeletal muscle liver cardiac cells
30
role of cAMP in the activation of phosphorylase
adrenaline induced secondary messenger that leads to the activation of phosphorylase
31
what is the function of the N-terminus and c1 and c2 regions of adenyl-cyclase
important for regulation by Galpha-GTP Complex signalling in mammalian cells
32
which forms of adenylate cyclase are activated by calmodium/Ca2+ and inhibited by Ca2+
activated: - III - V - VIII inhibited: - I - VI
33
what does the GPCR-ligand stimulate
conversion of GDP to GDP at the Gα subunit
34
what do the GTP conversion stimulate
dissociation of Gα from the beta/gamma subunits
35
what stimulates adenylate cyclase
a dissociated Gα subunit
36
what does intrinsic or stimulated GTPase activity cause
return of Gα to resting state and association with beta/gamma subunits
37
structure of protein kinase A (PKA)
consists of 2 regulatory subunits - inactive form (R2-C2) 2 catalytic subunits - active form - (C2)
38
what is allosteric activation
when cAMP activates PKA by dissociating the R subunits from the R2-C2 complex
39
what does the R-subunit of PKA contain
pseudosubstrate-sequence
40
what does cAMP dependant PKA target and what does it lead to
phosphorylase kinase leads to glycogenolysis
41
what precisely causes the conformational change of phosphorylase kinase
phosphorylation of serine 14
42
how are receptors desensitised to switch of GPCR and cAMP signalling
GPCR N-terminal is phosphorylated by beta-adrenergic receptor kinase
43
what do phosphorylated GPCR N-terminal tails recruit and what do they do
beta-arrestin attenuates heterotrimeric G-protein activation induces receptor internalisation
44
how is Gα deactivation achieved
intrinsic or GAP stimulated GTPase activity
45
what does GTP hydrolysis cause
stops activation of downstream targets causes re-association of Gα with beta/gamma subunits
46
how is cAMP deactivation achieved
activation of phosphodiesterase (PDE) hydrolysis of cAMP to generate AMP
47
what do PKA phosphorylates signal to in terms of fatty acids
hormone sensitive lipase (HSL) perilipin
48
what is the function of HSL
leads to translocation to lipid droplet and its activation
49
function of perilipin and what inhibits it
acts as a barrier to lipid hydrolysis phosphorylation
50
how does beta-adrenergic signalling stimulate increased heart rate and force step 1
the Ca1.2 channel increases Ca2+ influx in response to depolarisation
51
how does beta-adrenergic signalling stimulate increased heart rate and force step 2
the ryanodine receptor (RYR) stimulated increased calcium induced calcium released from the sarcoplasmic reticulum increased heart force
52
function of phospholambam and what does it lead to
prevents it from inhibiting SERCA mediated Ca2+ uptake enables faster relaxation for next contraction faster HR
53
what is a-kinase anchoring protein (AKAP)
contribute to spatial and selective restriction PKA signalling
54
what does cholera toxin switch on
Gs-coupled proteins
55
what switches off Gi-coupled protiens
pertussis toxin
56
what adrenergic receptors does adrenaline act on for lipolysis
β3/α2 receptors in adipose
57
what does Gαq activate
phospholipase C (PLC) to regulate downstream smooth muscle cell contraction
58
Structure of phosphatidylinositol(4,5)bisphosphate (PtdIns(4,5)P2)
Favoured chair structure has 5 equatorial OH and 1 axial oh. Consider a turtle with its head as the axial OH then the glycerol is connected to the right flipper which is position 1.
59
what does α-1 adrenoceptors act as
act as GEF for Gαq leads to PLC activation and Ptdlns4,5P2 hydrolysis leads to contraction and vasoconstriction
60
how is PLCβ1/3 activated
PLCβ1 - activated by Gαq PLCβ3 - activated by β and gamma subunits
61
how is PLCγ1 activated
Tyrosine phosphorylated receptor interacts with SH2 domain of PLCγ1. PLCγ1 is then tyrosine phosphorylated and activated
62
GPCR activate PLC mediated hydrolysis of PtdIns(4,5)P2 to produce what
to generate two new second messengers Diacylglycerol (DAG) and Ins(1,4,5)P3
63
features of lns(1,4,5)P3
water-soluble molecule and diffuses across the cytoplasm to the IP3 receptor which is found on the membrane of the endoplasmic reticulum
64
features of lns(1,4,5)P3-receptor
ligand-gated ion channel that allows the influx of calcium cations upon activation 3 isoforms exist
65
structure of lns(1,4,5)P3-receptor
made of a tetramer: - N-terminal Ins(1,4,5)P3binding domain - Coupling domain - Transmembrane domain - Gatekeeper domain
66
how is Ins(1,4,5)P3-Receptor activated
IP3 binds to the binding domain on the cytosolic face leads to conformational changes channel is opened calcium influx
67
what downstream target is activated in response to increase in diacylglycerol (DAG)
Protein Kinase C (PKC)
68
what relieves psuedosubstrate inhibition
DAG and Ca2+ at the membrane induce conformational changes
69
what is PKC regulated by and what is its function
receptor for activated C-kinase (RACK) regulates downstream phosphorylation
70
what is EPAC (exchange protein directly activated by cAMP)
EPAC is a guanine nucleotide exchange factor (GEF) that binds cAMP which induces a conformational change to activate its GEF activity
71
which has a higher lower affinity for cAMP PKA or EPAC and what does it mean
EPAC only activated at high concentrations
72
what is RAP
a small molecular weight G-protein acts as a molecular switch to regulate cytoskeletal dynamics, cell adhesion and secretion
73
what family does the insulin receptor belong to
tyrosine kinase receptor superfamily
74
what does ligand induced dimerisation of tyrosine receptor induce
cross phosphorylation increased kinase activity further receptor tail phosphorylation
75
purpose of the activation-loop phosphorylation
stabilises the active conformation of the insulin receptor tyrosine kinase (IRK)
76
what is P85 and what does it lead to
a regulatory subunit of PI3K contains an SH2 domain when bound to the receptor PI3K becomes active generates PIP3
77
what does the SH2 domain of P85 also recruit
PLCγ to the phosphorylated receptor activates PLCγ generates DAG and IP3
78
function of the SH2 domain of Grb2
mediates recruitment and subsequent activation of the RAS/MAPK pathway
79
what does tyrosine phosphorylation lead to
receptor ubiquination and internalisation
80
how is ubiquitin coupled to tyrosine phosphorylation
via the SH2 domain of casitas B-lineage lymphoma (Cbl protein)
81
what is the agonist lipid secondary messenger
Ptdlns(3,4,5)P
82
what is PTEN and what does it do
a tumour suppressant removes the 3 phosphate from Ptdlns3,4,5P3
83
what is SHIP1/2
a 5-phosphatase removes the 5 phosphate from Ptdlns3,4,5P3
84
what does SHIP generate
Ptdlns3,4P2 has messenger functions
85
interaction of Class 1A p110 catalytic domain with p85 regulatory domain causes what
suppression of p110 subunit activity prevents proteolytic degradation of p110 enables recruitment of holoenzyme to activated RTK receptor
86
what enables the coupling of tyrosine kinase receptor to class 1A PI3K
the SH2 domain of p85 interaction with specific tyrosine phosphorylated receptor peptide
87
what drives the synthesis of PIP3
SH2 mediated activation of PI3-kinase
88
function of GRB2
is an adapter protein DH2 domain binds to specific tyrosine phosphorylated residues on an RTK
89
what does GRB2 recruit and how
recruits the SOS protein via interaction with its SH3 domain with the proline-rich domain on the SOS protein
90
what is SOS and what enhances it
guanine nucleotide exchange factor for RAS activity is enhanced by interaction with the PH domain of Ptdlns4,5P2
91
what leads to conformational changes in RAS and what does it allow
GTP exchange enables reader interaction
92
what does the binary switch action of RAS cause (in terms of regulation)
converts GTP binding into the regulation of protein phosphorylation driven by the RAF/MAP kinase pathway
93
in terms of activation, what does the binary switch action of RAS cause
converts GTP binding into the activation of PI3K and PtdIns(3,4,5)P3 signalling
94
what does deregulation of RAS signalling lead to
cell proliferation and tumours
95
what specific mutations lead to RAS GTP accumulation
Gln61 Gly12

Biomed 2 (18 decks)

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