Cell signalling - created from Mind Map

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Extracellular signal molecules

Distance

Gap Junctions

Different cells can respond differently to the same signal

Types of receptors

Second Messengers

Response time

Feed back

Hydrophobic molecules

Hydropholic molecules

Intracellular receptors

Pass across membrane

Cell-surface receptors

Ligand

Short

Long

Contact dependent

Local mediators on neihbouring cells

Paracrine

Autocrine

Synaptic

Endocrine

Narrow water-filled channels

Direct communication bypassing plasma membrane barrier

Two-way communication

Homogenise intracellular conditions

Spread effects of extracellular signals through small molecules

Ca2+

Cyclic AMP

Due to different intracellular machinery

eg. acetylcholine

responds to specific combinations of signals

interprets

integrates

Decreases action potential in heart muscle

stimulates contraction in skeletal muscle

Intracellular receptors

Cell surface receptors

Nuclear receptors

Bind small hydrophobic molecules

ligand-modulated gene regulatory proteins

Steroid hormones

alter ability of receptor to control transcription of gene

Activates or inhibits bind DNA & transcription

Retinoids

Vitamin D

Ion-channel-coupled receptors

G-protein-coupled receptors

Enzyme-coupled receptors

Act as signal transducers

aka transmitter-gated

ionotropic receptors

Rapid signalling

mediated by transmitters

multipass transmembrane protein

open or close channel

GPCR

Senses outside cell, activate intracellular pathways

Indirectly regulates another membrane-bound target protein

G-protein mediates interaction between an activated receptor and the target protein

Multipass transmembrane proteins

Largest family of cell-surface receptors

Same signal molecule can activate many GPCRs

Half of all known drugs work through them or the pathways they activate

Some regulate the production of cAMP

Enzyme

Ion channel

trimeric GTP-binding protein

Relays signals from GPCR

7 TM domains

function directly asn enzyme

associate with enzymes that they acticate

single-pass TM proteins

Protein kinases or associate with protein kinases

6 principal classes

Ligand binding site on outside

Activating site inside

Receptor tyrosine kinases

Phosphorylates tyrosines on themselves and on some intracellular signalling proteins

TTKs

~60 genes encode human RTKs

Ligand binding causes RTK to dimerise, bring two kinase domains close together

Cross phosphorylate each other on multiple tyrosines

GTPase Ras mediates signalling

Ras superfamily consists of monomeric GTPases

intracellular signalling molecules

Initiators of intracellular signal transduction cascades

Bind to & alter intracellular signalling proteins or effector proteins

Intracellular signalling proteins

Molecular switrches

From inactive to active onformation when receiving a signal

Two classes

Depend on gain or loss phosphate

signaling by phosphorylation

Signaling by GTP binding

protein kinase

Protein phosphatase

GTP binding

GTP hydrolysis

Quickest synaptic

Quick movement, secretion, metabolism

Slow change ene expression

Positive

Negative

Output stimulates its own production

Steep or all-or-non response

Can persist after signal drops

Output inhibits its own production

Limit level of response

Short delay, brief abrupt response

Long delay, oscillations