Intracellular Signalling (session 2) Flashcards

1
Q

What is signal transduction?

A

Transmission of molecular signals from a cell’s exterior to its interior

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2
Q

What are the three superfamilies of cell surface receptor?

A

G protein-coupled (7TM (transmembrane)) receptors
Ligand-gated (receptor operated) ion channels
Receptors with intrinsic enzymatic activity (heterogenous receptor)

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3
Q

What are GPCR agonists?

A

Bind to receptor and activate it, leading to intracellular signal transduction events. Have affinity and efficacy

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4
Q

What are GPCR antagonists?

A

Bind to receptor but do not activate it (block effects of agonists at receptor). Have affinity but no efficacy

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5
Q

What is an example of a GPCR agonist?

A

Salbutamol and analgesia/anaesthesia

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6
Q

What is an example of GPCR antagonist?

A

Cardiovascular and neuroleptics (anti-schizophrenic)

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7
Q

What do different GPCRs respond to?

A

Ions (H+ and Ca2+)
Neurotransmitters (ACh, glutamate)
Peptide and non-peptide hormones (glucagon and adrenaline)
Large glycoproteins (thyroid-stimulating hormone)

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8
Q

What is the common basic structure shared by all GPCRs?

A
Single polypeptide chain (300-1200AAs), also called serpentine
7-TM spanning regions
Extracellular N terminal
Intracellular C terminal
Varying size of N and C
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9
Q

How do GPCRs cause change in cellular activity?

A

~Activated GPCR must interact with G protein
~GPCR-G protein (guanine nucleotide exchange factor (GEF)) interaction activates G protein by causing GTP to exchange for GDP on G protein alpha subunit-GTP replaces GDP because high conc of GTP in cells
~alpha-beta/gamma complex dissociates and each interact with effector proteins
~GTPase hydrolyses GTP back to GDP and alpha-GTP an beta/gamma subunits reform

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10
Q

What are the subunits that G proteins are made of?

A

Alpha
Beta
Gamma

(Structurally trimeric but functionally dimeric so alpha and beta/gamma)

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11
Q

Name effectors that are also enzymes

A

Adenylyl cyclase
Phospholipase C
PI3K
cGMP phosphodiesterase

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12
Q

Name effectors that are ion channels

A

Voltage-operated Ca2+ channels (VOCCs)

G protein-regulated inwardly-rectifying K+ channels (GIRKs)

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13
Q

Which reaction does adenylyl cyclase catalyse?

A

ATP -> cyclic AMP

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14
Q

Which reaction does phospholipase C catalyse?

A

PIP2 -> IP3 + DAG (diacyl glycerol)

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15
Q

Define inotropy

A

Force with which heart contracts

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16
Q

What is positive inotropy?

A

Blood-borne adrenaline and sympathetically released noradrenaline interact with ventricular beta1-adrenoceptors to increase force of contraction

17
Q

In the CNS and PNS, what modulates neurotransmitter release?

A

Presynaptic GPCRs

18
Q

Why does the “receptor -> G protein -> effector” reaction happen on the plasma membrane?

A

It concentrates all the components on the same domain.

19
Q

Which Gs coupled receptors stimulate adenylyl cyclase? (3)

A

Beta-adrenoceptors
D1 dopamine receptors
H2 histamine receptors

20
Q

Which Gi coupled receptors inhibit adenylyl cyclase?

A

Alpha2-adrenoceptors
D2 dopamine receptors
Mu opioid receptors

21
Q

What do the R and C subunits of cAMP do?

A

R=regulates the C subunit

C=catalytic subunit, phosphorylates target proteins in the cell

22
Q

What effect does IP3R activation have on cytoplasmic [Ca2+]?

A

Increases [Ca2+] by 5-10 fold (from 1 x 10-7 M) within a few seconds of agonist addition

23
Q

Which Gq coupled receptors stimulate phospholipase C?

A

Alpha1-adrenoceptors
M1 muscarinic receptors
H1 histamine receptors