IVC Classes of Cell Surface Receptors

Three Classes of Cell surface Receptors

1. ION-CHANNEL-LINKED RECEPTORS

2. G-PROTEIN-LINKED RECEPTORS

3. ENZYME-LINKED RECEPTORS

which of the three classes of cell surface receptors are Ligand Gated Channels

Ion-Channel Linked Receptors

what kind of transmembrane family of proteins are ion gated channel linked proteins

multipass transmembrane ( has 4 components )

what is the effect of ions or ligands binding to the receptor ( ion channel linked receptors )

changing confirmation of the receptor so that ions can pass though

What is the effect if ions pass through the ion channel linked receptors to he cell

change in electric potential across the membrane

What kind of receptors are nicotinic acetylcholine receptors ( acetylcholine here is a neurotransmitter signal )

ion-channel linked receptors

what does multipass proteins mean

the protein passes through the membrane multiple times to create the transmembrane protein

define the structure of the nicotinic acetylcholine receptors

• has 4 subunits ( a,a,y,s)

• larger domain for extracellular side (6nm)

• smaller domain for cytosolic side (2nm)

• diameter 9nm

Nicotinic acetylcholine receptor and muscle contraction process

1. action potential coming from the presynaptic motor neuron containing acetylcholine → induces opening of voltage gated Ca2+ channels in the motor neuron, releasing Vesicle with acetylcholine

2. acetylcholine binds to Nicotonic acetylcholine receptor to the target cell, allowing the opening of the opening of the gate

3. influx of Na+ produces a localized depolarization of the membrane, leading to opening of more voltage-gated Na+ channels and

   generation of an action potential

4. depolarization reaches T tubules, it is sensed by voltage-gated Ca2+ channels in the

   plasma membrane. This leads to opening of Ca2+ - release channels in the sarcoplasmic reticulum membrane, releasing stored Ca2+ into the cytosol

5. The resulting rise in cytosolic Ca2+ causes

   muscle contraction.

the largest family of cell-surface receptors

G-PROTEIN-LINKED RECEPTORS

what kind of receptors are receptors for epinephrine

G-PROTEIN-LINKED RECEPTORS

what kind of receptors are for serotonin

G-PROTEIN-LINKED RECEPTORS

what kind of receptors are for glucagon

G-PROTEIN-LINKED RECEPTORS

what type of proteins are G-PROTEIN-LINKED RECEPTORS

seven pass transmembrane protein with alternating cytosolic and extracellular loops

what are the purpose of the extracellular and cytosolic portion of the G-PROTEIN-LINKED RECEPTORS

• extracellular portion: binding site for ligand

• cytosolic portion: binds a specific G- protein

what kind of receptors are for most of the neuron’s receptor

G-PROTEIN-LINKED RECEPTORS

What is the structure of G-proteins

composed of subunits a,b,y

How G-protein-linked receptor works

1. ligand binding to receptors

2. change in receptor conformation

3. activation of g protein

4. binding of activated g-protein (specifically Ga subunit )to receptor

5. binding induces a conformational change in Ga, bound GDP dissociates and is replaced by GTP, Ga dissociates from Gby

6. Ga GTP activated binds to active effector

7. generation of a second messenger or change in membrane potential

8. Hormone dissociates from receptor

9. Hydrolysis of GTP to GDP causes Ga to dissociate from the effector and reassociate with Gby

these are GTP-binding proteins that are attached to the cytoplasmic face of the PM that gets activated once there is a change in conformation upon the formation of the ligand-receptor complex

G-proteins

what is the structure of G-proteins

made up of three subunits (trimeric protein)

Gα, Gb + Gγ = Gbγ

This subunit of the G-protein is a GTPase switch protein

Ga

how does the switch of the Ga as a subunit of G-proteins work

OFF when bound to GDP

ON when bound with GTP

This subunit of the G-protein when dissociated with Gα, this newly exposed surface is now free to interact with other signaling proteins, enabling downstream cellular responses.

GBy

This is termed to be the relay molecule as it couples its receptor to enzymes or ion channels

G-protein

True or false: G-proteins are specific for a specific receptor and for a specific set of downstream target / effector proteins

TRue

what are the two general pathways G-proteins induces

1. cAMP path way - stimulating pathway ( Gs protein )

2. ca2+ pathway - inhibitory pathway (Gi protein )

this is the stimulatory G protein

Gs

This is the inhibitory G protein

Gi

how does the stimulatory pathway or the cAMP pathway get induced

1. Stimulatory signal or Hormone: Epinephrine Glucagon ACTH

2. binds to receptor for stimulatory hormone

3. stimulatory G-protein complex binds to receptor

4. Ga binds to Adenylyl cyclase (Effector protein )

5. produces cAMP

how does the inhibitory pathway or the cAMP pathway get induced

1. Inhibitory signal or Hormone: PGE1 Adenosine

2. binds to receptor for inhibitory hormone

3. inhibitory G-protein complex binds to receptor

4. Ga binds to Adenylyl cyclase (Effector protein )

5. ion channels gets regulated since there is no production of cAMP

different types of Ga subunit and their different effects

Gia - ion channels inhibition cAMP, phospholipases

Gsa - increase cAMP

Gqa - increases DAG IP3

G12,13 a - Activates Rho

what do you call the GBy subunits specifically

Ion channels P13k, Phospholipases Adenylylacylases Receptor kinases

how does the amplification by epinephrine go about

1. Epinephrine (1:3)

2. Adenylyl cyclase (1:10)

3. cAMP (2:1)

4. Protein Kinase A (1:5)

5. Activated Enzyme (1:5)

6. Product

true or false: When an egg is fertilized by a sperm embryonic development is initiated and entry of other sperms is prevented

True

what do you call the inhibitory pathway for cAMP that induces the elevation of cytosolic Ca2+

IP3/DAG Pathway

what is the effector enzyme for cAMP pathway and Ca2+ pathway

1. Adenylyl cyclase E

2. Phospholipase C

meaning of PIP2

phosphoinositol biphosphate

IP3 meaning

Inositol triphosphate

meaning of DAG

Diacyglycerol

process of IP3/DAG Pathway

1. Izumo (sperm signal) triggers Juno (egg) egg receptor which activates a tyrosine kinase pathway

2. activation of Phospholipase C which will act on pip2

3. IP3 and DAG are produced from PIP2, IP3 is recognized by IP3 receptor on the nucleosome, opeing the IP3 gated Ca2+ channel

4. Triggers the release of Ca2+ and cam → CAMK

5. Ca2+ binds to protein kinase C

6. PKC binds with DAG and phosphorylation of PKC occurs

7. IP3 Gated ca2+ channels directly binds to store operated TRP ca2+ channel to release ca2+ into the extracellular side

zinc spark

please study this video link

this class of cell surface receptors are a single pass transmembrane proteins

Enzyme linked receptors

Two functions of enzyme linked receptors

1. function directly as enzymes

2. directly associated with enzymes as they activate

2 major groups of ELRs

1. Receptors lacking intrinsic catalytic activity but directly associated with cytosolic tyrosine kinases or histidine kinases

2. receptors with intrinsic enzymatic activity

What is the effect of ligand binding to receptors when it comes to ELRs with receptors with intrinsic enzymatic activity

1. dimerization of receptor monomer

2. activation of the enzyme activity of the receptor in its cytosolic domain

3. some can undergo autophosphorylation

what kind of receptors that can undergo autophosphorylation as receptors with intrinsic enzymatic activity

receptors for Insulin, EGF and TGF (B)

What type of receptors are receptors for tyrosine kinase

ELR (Receptors with intrinsic enzymatic activity)

What type of receptors are receptors for tyrosine phosphatases

ELR (Receptors with intrinsic enzymatic activity)

what type of receptors are receptors for serine/ threonine kinases

ELR (Receptors with intrinsic enzymatic activity)

what type of receptors are for receptor for guanylyl cyclase

how does the tyrosine kinase receptor go about

1. tyrosine kinase receptor proteins inactive monomers are undimerized and contains tyrosine

2. activation of the tyrosine kinase receptor occurs in the presence of ATP, signal molecule and activated proteins, forming a dimer

3. cellular response

what is the effect of ligand binding to receptors in ELRS, specifically Receptors lacking intrinsic catalytic activity but directly associated with cytosolic tyrosine kinases or histidine kinases.

binding of ligand dimerizes and activates the receptor which interacts with certain cytosolic protein kinases

what are the examples of the receptors for ELRS, specifically Receptors lacking intrinsic catalytic activity but directly associated with cytosolic tyrosine kinases or histidine kinases.

receptors for cytokines, interferon and erythropoietin

how does the interferon receptors go about

1. Binding of a-Interferon ( the signal ) crosslinks adjacent receptors, Jaks also cross phosphorylate each other on tyrosines

2. activated jaks phosphorylate receptors on tyrosines

3. after STATs dock on specific phosphotyrosines on the receptor, the Jaks phosphorylates them

4. STATs dissociate from receptor and dimerize via their SH2 DOMAIN

5. STATs migrate to nucleus, bind to DNA and other gene regulatory proteins

study fucking ethyropoietin receptor

okay

study cytokine receptors

okay