Intracellular Signalling Flashcards Preview

Cell Biology And Signaling > Intracellular Signalling > Flashcards

Flashcards in Intracellular Signalling Deck (28)
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1

Definition of endocrine

Signal produced by cells in 1 body part, travels in blood to target cells elsewhere

2

Definition of autocrine

Signal acts on same cell that produces it

3

Definition of paracrine

Signal produced by cell, acts on cells close by

4

Definition of contact dependent

Signal is integral part of 1 cell, interacts directly with another cell

5

Definition of neuronal

Electrical signal transmitted down cell, message passed to another via synapse

6

Definition of G proteins

Guanine nucleotide binding proteins act as molecular switches inside cells. Involved in transmitting signals

7

Function of cellular responses

Change metabolic activités
Secrete and release
Changes in gene expression
Sensory perception

8

Factors that act as extracellular signals

Amino acids + derivatives
Steroids
Prostaglandins (eicosanoids)
Proteins and peptides
Gases

9

How cells signal to each other

Endocrine
Autocrine
Paracrine
Contact dependent
Neuronal

10

Characteristics of receptors/signals

Receptor must be expressed in order to respond to signal
High selectivity and affinity
Signal can bind to different receptor types
Signal eventually turned off

11

Location of receptors

Cell surface
Intracellular receptors

12

What happens with a receptor on the cell surface

Hydrophilic hormone
Binding triggers internal response without hormone entering

13

What happens with an intracellular receptor

Hydrophobic hormone
Binds to internal receptor, triggers internal response
Crosses plasma membrane

14

Types of signalling

Binding of signal to receptor by
Depolarization of signal to receptor due to ion flow
Direct transcription factor activation
Generation of 2ndary message in cell
Direct activation of enzymatic kinase cascade

15

What happens in depolarization of membrane due to ion flow?

Ach (signal) binds to nicotinic acetylcholine receptor
Ion channel opes to allow Na+, K+, Ca2+ in

16

What do steroid hormones have?

Hormone binding domains
DNA binding domain
Interacting with other transcription factors domain

17

What happens in direct activation of transcription factors

Binding of steroid induces conformational change, allows DNA binding, activation of target gene transcription
DNA binding domain is sequence specific
Transcription factors = ligand dependent

18

What is the secondary messenger model

Signal binds to transmembrane receptor (1st messenger)
Triggers other molecules in the cell, (acts as 2nd messenger)

19

Structure of guanine nucleotide binding proteins

Inactive state, aby
Dissociates into a by when GDP binds
Free active a subunit activates effector enzymes

20

Location of the G protein coupled receptor

Transmembrane a helix with 7 proteins

21

GPCR signalling to effector enzymes

Signal binds to receptor
G protein (GDP bound) associates w receptor
GTP/GDP exchange on G protein (GTP bound)
G proteins dissociate into a (GTP bound) and by subunits
a (GTP bound activates effector enzyme
Effector produces 2nd messenger
GTP hydrolyses to GDP, G proteins complex reassociates, end of signal

22

Structure of cAMP dependent protein kinase A (PKA)

Tetrameric enzyme, 2 regulatory, 2 catalytic subunits (r2c2)
When cAMP binds to both r, activates c subunits

23

How does CREB affect gene transcription?

PKA phosphorylates cAMP response element binding protein (CREB)
CREB binds to specific sequences in target genes, transcription stimulated
Gene expression can change if change is long term (starvation)

24

GPCR and IP3/DAG signalling

Signal molecule activates GPCR
Activated G protein a subunit activates phospholipase C
Activated phospholipase C cleaves IP3 from DAG
IP3 activates Ca2+ channel
DAG + Ca2+ activates PKC

25

Direct activation of enzymatic kinase cascade

Binding of EGF => dimerisation of intracellular domains => autophosphorylation of tyrosines

Tyr <= SH2 <= GRB2 <= SOS

Ras is broken down from GDP => GTP and triggers MAPKKK cascade

26

Ras

Monomeric G protein
GTP-Ras triggers kinase cascade
Has no 2ndary messenger
GDP-Ras => GTP-Ras

27

What is the Ras-MAP-kinase pathway

Mitogen activated protein kinase kinase kinase (MAPKKK) activates MAPKK
Activates MAPK
Activates transcription factor

28

GPCR and cAMP pathway

Molecule binds to extracellular binding GCPR site
Dissociated GTPa unit activates adenylyl cyclase
AC converts ATP => cAMP
cAMP activates PKA
PKA can activate CREB which affects transcription