Neurobiology Cell Signaling

Front 1

Four receptor mechanisms

Back 1

Ion channel
Receptor enzyme
G proteins
Transcription factor

Front 2

Ion channel general workings

Back 2

The binding of the ligand (message molecule) to an extracellular domain of the receptor opens the channel domain of the receptor and ions flow into (or out of) the cell.

Front 3

Receptor enzyme general workings

Back 3

The ligand binding to an extracellular domain of the receptor induces activation of an intracellular catalytic domain

Front 4

G proteins general workings

Back 4

The ligand activates the receptor to interact with a G protein which in turn activates membrane bound enzymes or ion channels (somewhat alike to enzymes or ion channels, but with an intermediate step)

Front 5

transcription factor general workings

Back 5

When activated by the ligand (which in this case goes into the cell), binds to promoter regions of genes and induces gene transcription

Front 6

Hydrophilicity/phobicity of four receptor mechanisms

Back 6

Ion channel, receptor enzyme and G proteins are hydrophilic; the (first) messenger binds outside the cell and never enters.

Transcription factor features hydrophobic (first) messengers which enter the cell.

Front 7

Ion channel structure

Back 7

Membrane proteins

4 or 5 subunits in a ring, forming a pore

Front 8

Ion channel opening mechanisms
(subunits, ion pecificity)

Back 8

binding of a ligand (5 subunits, not very ion specific)

membrane potential (4 subunits, specific to one ion type)

(More subunits -> larger pore -> less specific)

Front 9

Ion flow direction

Back 9

Depends on concentration of the ion and on the charge

Front 10

Resting potential magnitude
K, Na, Ca, Cl

Back 10

-50 to -70 mV (negative charges are pulled towards the inside)

K and Na travel with the electrical gradient

Ca and Cl travel against the electrical gradient, with the chemical gradient (hyperpolarization)

Front 11

Na+/K+-ATPase

Back 11

Creates resting potential by pumping 3 Na OUT and 2 K IN, consuming ATP

Front 12

Nicotinic receptor
(subunits, binding)

Back 12

ion channel receptor reacting to neurotransmitter acetylcholine

Five subunits
- 2 alpha which each bind acetylcholine
- 3 comparable beta/gamma/delta subunits, they were all derived originally from the same gene, expressions (and so also properties) vary depending on the cell

Front 13

Classical vs recombinant sequencing

Back 13

Classical needs a lot of purification, each time losing protein, whereas recombinant multiplies the sequence during several steps, giving enough signal to sequence membrane receptors (which have low concentration).

Front 14

Recombinant protein multiplication

Back 14

mRNA for the protein transcribed to cDNA and implanted in bacteria to multiply it

Front 15

Hydropathy profile

Back 15

Every amino acid in protein given a hydrophobicity rating; hydrophobic sequences may be membrane spanning area's (especially if ~25 acids)

Front 16

Protein across membrane
(length, structure)

Back 16

About 25 hydrophobic amino acids are needed because crossing happens in an alpha-helix

Front 17

Determining N-terminal of membrane receptors

Back 17

N-terminal is always extracellular

Front 18

GABA
function, prevalence

Back 18

Most important inhibitory neurotransmitter in the brain
(45% of brain)

Front 19

GABA
synthesis

Back 19

Synthesised (1 step) from glutamate (which is itself a neurotransmitter)

Front 20

GABA types

Back 20

GABAa: ion (Cl) channel
GABAb: G-protein coupled receptor

Front 21

GABA + glutamate

Back 21

Both neurotransmitters, both very prominent in the CNS (70% total!)

GABA is inhibitory

Front 22

neurotransmitter: is it ion channels or G protein receptors

Back 22

without exception, neurotransmitters which possess ion channel receptors also possess G-protein coupled receptors

Front 23

ionotropic vs metabotropic timing

Back 23

ionotropic / ion channels: fast and short lasting (just reverse membrane potential)

metabotropic / G coupled: slow and long lasting (kinases are activated)

Front 24

GABAa structure

Back 24

two alpha, two beta, one gamma subunit

binding in beta subunits

Front 25

Ion filter

Back 25

Charge within ion channel pore allows only anions or cations to go through

Front 26

GABAa ligands

Back 26

GABAa has many ligands with different binding sites and affinities. Some (benzodiazepine) may only enhance the effect of others

Front 27

benzodiazepine

Back 27

Reduce anxiety

Interact with GABAa. No effect alone, but makes GABA effect stronger and longer (potentiation)

Front 28

potentiation

Back 28

One signalling molecule making another more potent (by interacting with the receptor)

Front 29

GABAa
genetics

Back 29

There are different genetic versions of each of the subunits. It looks like there are several (~10) different GABAa receptors active in the CNS. Functionality is also effected, e.g. sensetivity to benzodiazepine

Front 30

Glutamate
synthesis

Back 30

Glutamic acid (neutral form of glutamate) is a standard amino acid (non-essential)

There are very many subtypes

Front 31

Glutamate
function

Back 31

long-term potentiation and is important for learning and memory

Front 32

NMDA vs non-NMDA

Back 32

Glutamate receptors

NMDA: Ca2+; N-methyl-D-aspartate is agonist

Non-NMDA: Na+

Front 33

agonist

Back 33

increases the signal transduction activity of a cell when bound to a receptor on that cell