[BiochemB] Signal Transduction - Dr. Viliran (Bernabe and Dela Rosa).pdf

BIOCHEMISTRY B – SIGNAL TRANSDUCTION | FEU-NRMF | Dela Rosa, Hannah Maree & Bernabe, Maria Katrina

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SIGNAL TRANSDUCTION/INTRODUCTION

It is a way of cell to cell communication SIGNAL TRASDUCTION

from the word “transduce” it is the process of converting extracellular signal to

an intracellular response process of converting one form to another -- one

form of energy to another form of energy Example: Dr. Viliran communicating to us through

speaking and you as the students, how will you accept the signal and how are you going to interpret the signal? Through listening and answering

What is the energy used by Dr. Viliran in speaking? Sound waves

How are the students able to listen? Through the organ of corti. Sound energy is converted to mechanical energy

Signal Transduction is cell signaling or “cell talk”

CELL SIGNALLING How do cells receive and respond to signals from their

surroundings? Prokaryotes(unicellular organism) and unicellular

eukaryotes are largely independent and autonomous

Multicellular organisms need intercellular integration and coordination of cell functions by way of signaling molecules that are secreted or expressed on the cell surface of one cell and bind to receptors expressed by other cells.

If there are signaling molecules, there should be something to accept the signal; and we call these RECEPTORS expressed by other cells.

You learned before the importance of the gene which is being expressed to produce proteins. You produce chemical substances through gene expression, and the secreting molecule will now communicate with another cell through interaction with receptors. These cells will produce a response now converting it into a intracellular response. When it produces protein it will interact with another cell. CELL TO CELL COMMUNICATION

Send Signals as Hormones (“speak”) Type of Compound/Classification

Steroid (derived from cholesterol) Peptide, Protein Amine (derived from amino acids)

NEP, EP Target

Organ, Tissue, Cell (Another Cell or Same Cell)

Receive Signals through Receptors (“hear”)

Protein Glycoprotein

HOW A GENE SPEAKS and EXPRESS ITSELF/GENE EXPRESSION

With Transcription, you produce a heterogenous nuclear RNA, which will undergo further processing (splicing, capping, adenylation) then you have the mature RNA. Then from the nucleus, it goes to the cytoplasm and mRNA acts as a template for translation and you produce the protein.

Inside the cell, we have here the signaling molecule interacting with the receptor usually on the cell membrane. This is the first part of the signal transduction pathways and then binding of the signaling molecule or the first messenger with the receptor will cause conformational change that will lead to activation of proteins functioning as Transcription Factors. Eventually it will stimulate the gene for expression; either synthesis of different transcription factors or synthesis of proteins that we gave the cells response to the first messenger. Transcription factors also help in expression of other genes.

Signal is received by other cell which needs to be amplified and then it will have a greater effect. And then Transduction, this will be converted into a cellular response. The response can also affect the signaling molecule (Negative Feedback).

SIGNAL TRANSDUCTION

Dr. Viliran


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EXAMPLE of AMPLIFICATION in the cAMP SYSTEM

For example here, you have the Messenger-receptor. A very good example of it is GLUCAGON or EPINEPHRINE

interacting with a receptor. Then glucagon or epinephrine will activate the enzyme

ADENYL CYCLASE. And what is the role of adenyl cyclase? It coverts ATP to cyclic

AMP. So there is increased production of cyclic AMP. And take note the ratio, 1 signaling molecule activating 1

enzyme and that enzyme produces 100 cyclic AMP. Therefore, it is amplified.

Then once cAMP increases, it activates now the PROTEIN KINASE. So 1:1

And this activated protein kinase now phosphorylate the main function of phosphorylate enzyme, phosphorylate other enzyme 10x, so 10,000 enzymes and then the phosphorylated enzyme now will act to increase the glucose. (action of increased glucagon and NEP).

Expect that a molecule or glucagon will produce almost a million molecule of glucose.

SIGNAL GENERATING CELLS Epithelial Cells (mostly) Connective Tissue

Leydig cells Granulosa cells

Secretory Cells Neurons Glandular cells

RECEPTORS (located in cell membrane and inside the nucleus)

There are signals that can pass the cell membrane and then they work on the nucleus and directly on the DNA

There are signals mainly water soluble, they cannot pass the membrane, they are only located outside and the membrane receptor

Cell associated recognition molecule Provides high degree of discrimination by the target cells Functional domains/portions:

Recognition Domain Coupling Domain

(with DNA or another protein) Enzyme Domain

kinase cascade Steroid Receptors

Located INSIDE the cell Recognition domain binds hormone Coupling domain binds to

specific DNA region other proteins such as transcription

factors Activates/Represses gene

transcription

Membrane Receptors They are located OUTSIDE of the cell Extracellular recognition domain binds hormone Intramembrane

Channel function Intracellular

Coupling domain Enzymatic domain (signal transduction)

Water soluble, hydrophilic signaling molecules usually interact with these kinds of receptors.

Hydrophobic molecules can directly enter the cell straight to nucleus

FUNCTIONS/IMPORTANCE of SIGNALING MECHANISM

homeostasis or maintenance of physiological conditions growth and development reproduction mood memory energy production, storage and use metabolic control behavior acute response to infection, wounding production & differentiation of cells (e.g. blood cells) … any biological process

SIGNAL TRANSDUCTION

The process of converting extracellular signals into cellular responses.

Extracellular signaling molecules (ligands) - substances synthesized and released by signaling cells and produce a specific response only in target cells that have receptors for the signaling molecules

Another term used for signaling molecule is actually a LIGAND. The concept is ligand interacting with the receptor and you create several signaling molecules. This is what we call the second messengers. And a very popular second messenger is cyclic AMP. The receptor is the recipient.

You have a series of reaction, amplification and eventually that signal outside the cell reaches the DNA. And then you produce a corresponding cellular response

So you have here lipid soluble messenger; since it’s lipid soluble, the receptor is directly in the DNA. It can pass through the cell membrane and the nuclear membrane. And still, you have the response. Again, ligand interacts with receptor. It could be a protein or glycoprotein.

Receptor – a specific protein that specifically binds a

signaling molecule to initiate a response in a target cell Cell responses :

changes in gene expression


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cell morphology cell movements

Six steps in SIGNAL TRANSDUCTION: 1. You have to synthesize the signaling molecule by the cell. 2. Release of the signaling molecule by the signaling cell 3. transport of the signal to the target cell 4. Signal interacting with the target receptor on the other cell 5. Once you have the ligand (signal) and receptor interaction,

there will change in cellular metabolism, function, or development triggered by the receptor-signal complex

6. Removal of the signal because it is not a continuous signal which often terminates the cellular response.

For example, fasting and starvation. Glucagon works on the liver activating Glycogenolysis. When it reaches the correct glucose level, you have to terminate glycogenolysis and gluconeogenesis especially in prolonged starvation.

TYPES of SIGNALING:

ENDOCRINE SIGNALING signaling molecules (hormones) act on target cells

distant from their site of synthesis by cells of endocrine organs

For example, Adrenal Glands. They release cortisol, and then it acts on the liver. The pancreas releases insulin, which acts on different cells such as adipose cell, fat cells, liver.

PARACRINE SIGNALING the signaling molecules (neurotransmitters)

released by a cell only affect target cells in close proximity to it

Example: Acetylcholine AUTOCRINE SIGNALING

cells respond to substances (growth factors) which they themselves release

TWO GENERAL KINDS of CELL RECEPTORS: CELL SURFACE RECEPTORS LIGAND

– hydrophilic signaling molecules INTRACELLULAR RECEPTORS LIGAND

– Small hydrophobic signaling molecules – Remember that your cell membrane is composed of

two layers of lipid. Hydrophobic signaling molecules can pass through it.

Again, we have here the secretory cell producing signaling molecule or ligand interacting with the receptor.

As you can what is being shown here is the specificity of the ligand with the receptor. It cannot bind to cell B and C because the receptor is not appropriate. It only binds to Cell A, with the appropriate specific receptor. It demonstrates the ligand specificity to the receptor.

MEMORIZE!!!!!!! Dr. Viliran said that it will be a part of the Exam CLASSIFICATION of HORMONES based on SOLUBILITY and RECEPTOR LOCATION:

1. SMALL LIPOPHILIC MOLECULES that diffuse across the plasma membrane and interact with intracellular receptors

Steroids(cortisol,progesterone,estradiol,testosterone), thyroxine and retinoic acid

2. WATER-SOLUBLE HORMONES with cell-surface receptor Peptide hormones → insulin, growth factors,

glucagon Small charged molecules → epinephrine,histamine

3. LIPOPHILIC HORMONES WITH CELL SURFACE RECEPTORS → prostaglandins,thromboxane,leukotrienes (inflammatory mediators that usually act on the cell surface even though they are lipophilic)


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CLASSES of CELL SURFACE RECEPTORS:

1. G-protein coupled receptors (GTP-binding) GPCR Serpentine receptors E Example: epinephrine,serotonin, angiotensin,

vasopressin, bradykinin and glucagon receptors 2. Ion channel receptors

Example : Acetylcholine receptor 3. Tyrosine kinase-linked receptors that lack intrinsic

enzyme activity Ex: receptors for cytokines, interferons, and growth

factors 4. Receptors that penetrate the plasma membrane with

intrinsic enzymatic activity Ex: Tyrosine kinases ( PDGF, insulin ,EGF,FGF) Tyrosine phosphatases – CD45, T cells,macrophages Guanylate cyclases – activin, TGF-β receptors

Note: Memorize the examples/receptors and their corresponding receptors

(A) In the presence of the ligands such as Ach, there is change in the conformation of the receptor from a closed position, it will then open up. (B) G-protein linked receptor. GPCR. So this is your G-protein but upon binding of the ligand, this activates the protein. Example: Glucagon. So binding of this ligand glucagon to the receptor activates the G-protein. Once the G-protein is activated, it activates now the enzyme and then the active enzyme will have an effect on sugar. (C) Enzyme-linked Receptor. Insulin and the Growth Factors. So without the ligand, the catalytic domain or the enzyme is inactive. But upon binding of the ligand for example, insulin, this activates the enzyme.

So you have here the gated ion channel. It opens up with the ligand/signal binds to it. This is receptor enzyme activity. The enzyme is activated with the binding of the signal or the ligand.

Serpentine Receptor or G-protein coupled receptor. So binding of the ligand activates the G-protein which then activates the enzyme.

Receptor with no intrinsic enzyme activity. Adhesion Receptor. Steroid Receptor. It is direct. There are signals that can pass

the membrane and then it acts on the DNA.

FOUR FEATURES of SIGNAL-TRANSDUCING SYSTEMS a. Specificity

Particular signals specific to a particular receptor S1 will bind instead of S2

b. Amplification EP, Glucagon and Glucose You amplify the signal

c. Desensitization/Adaptation Negative Feedback inhibition just to control product formation

because if not there will be a lot of response d. Integration

You can have a lot of signals but it can be integrated S1 and S2 can be integrated but there is only one response

SECOND MESSENGERS

Binding of ligands to cell surface receptors leads to a short-lived inc. or dec. in the concentration of Intracellular signaling molecules termed second messengers 3’,5’ cyclic AMP (cAMP) 3’,5’ cyclic GMP (cGMP) 1,2 diacylglycerol (DAG) inositol 1,4,5 triphosphate (IP3) inositol phospholipid- phosphoinositides Calcium

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MAJOR PATHWAYS to GENERATE SECOND MESSENGERS

cAMP Pathway

Binding of ligand with G-protein coupled receptor It then activates the G-protein into a coupled receptor It then activates enzyme adenylate cyclase Then there is production of cAMP

Calcium Pathway Ligand-receptor interaction, GPCR because you have the G-

protein. Activation of the enzyme causing the release of Calcium Mainly it is phospholipase enzyme that is activated Release of Calcium Calcium interacts with protein Calmodulin

You have here cAMP production will cause phosphorylation of enzyme phosphorylase kinase. Once phosphorlated, it activates glycogen phosphorylase. Glycogen is then integrated to glucose. OTHER INTRACELLULAR SIGNALING PROTEINS in SIGNAL TRANSDUCTION:

1. GTPase Switch Proteins – GTP-binding proteins that act as molecular switches in signal transduction pathways

“ON” when bound to GTP “OFF” when bound to GDP Two classes of GTPase switch proteins:

a. Trimeric G protein – coupled directly to activated

receptors – BIGGER

b. Monomeric Ras and Ras-like proteins

– linked indirectly via other proteins (other protein in between)

– SMALLER 2. PROTEIN KINASES

carry out the process of phosphorylation opposed by the activity of protein phosphatases

3. ADAPTER PROTEINS no catalytic activity contain domains as docking sites for other protein

MAJOR INTRACELLULAR SIGNALING MECHANISMS

(A) Signaling by Phosphorylation. So you have the ligand. SIGNAL IN, So its ADP to a diphosphate. So it is phosphorylation, switching the signal into on position. (B) Signaling by GTP-Binding Protein. Signal again the ligand, if it is bound with GDP, OFF. Phosphorylation, so you have one phosphate here, it is now bound with GTP. ON. SIGNAL OUT.

So you have here, GPP, GPCR. Take note that the G-protein is not yet bound with your receptor. It is still inactive but upon binding of the ligand, when the G-protein will be activated, it will now interact with the receptor. Upon binding of the receptor with the G-protein, it becomes active, activating the enzyme. G PROTEINS (guanine nucleotide-binding proteins)

G protein-coupled receptors are transmembrane receptors. Signal molecules bind to a domain located outside the cell

G proteins regulate metabolic enzymes, ion channels, transporters, and other parts of the cell machinery, controlling transcription, motility, contractility, and secretion, which in turn regulate systemic functions such as embryonic development, learning and memory, and homeostasis


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SIGNALING via G-PROTEIN-COUPLED RECEPTORS (GPCR)

G-Proteins – GTP-binding proteins Trimeric proteins ( α β γ ) Coupled directly to activated receptors GTPases – convert GTP to GDP + Pi ACTIVE- when GTP is bound (ON) INACTIVE – when GDP is bound (OFF) ACTS AS MOLECULAR SWITCH

G-PROTEIN-COUPLED RECEPTOR/SERPENTINE

On the outside, you have here the domain or the signal interacting with the ligand. CELL’S RESPONSE

The receptor, the G-protein and ligand. Activation then activates the enzyme and the enzyme will cause these effects.

Once adenylyl cyclase is activated, ATP is converted to cAMP. cAMP now converts protein kinase. When it is phosphorylated, protein kinase becomes active phosphorylating other proteins and create cell response.

So you have here the α subunit and the β subunit and γ subunit. Which subunit has the binding site for GDP and the GTP?

It’s the α subunit This is where GTP binds when it is OFF and GDP when it is ON.

Binding of the ligand, then conformational change of receptor, exposing bing site for G-protein. Then GDP dissociates allowing GTP to bind and


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this causes the subunit to dissociate from the GS complex. The α subunit will dissociate then it will bind and activate the enzyme adenylate cyclase.

When the enzyme is active, cAMP is produced. And then it will go back to the original position, GTP is placed because the receptor has GTPase enzymatic activity. GTPase acts on GTP, converting it back to GDP.

Activate events altering concentrations of intracellular mediators (SECOND MESSENGERS)

Common second messengers: cyclic AMP (cAMP) Ca++

CYCLIC AMP (cAMP)

Second messenger produced from hydrolysis of pyrophosphate from ATP

Synthesized by Adenylyl Cyclase Degraded by cAMP phosphodiesterase by acting on

phosphodiester bond and cutting the phosphate to form 5’AMP.

CARBOHYDRATE METABOLISM REGULATION by cAMP

cAMP activates glycogen phosphorylase (glygenolysis) cAMP inhibits glycogen synthase (Glycogenesis) Insulin inhibits cAMP Glucagon and Epinephrine activates cAMP cAMP increases glucose Insulin promotes glycogenesis

Glucagon bound to receptor, production on cAMP, phosphorylation of protein kinase, then phosphorylating glycogen phosphorylase, then glucose is produced. No glucagon, activate glycogen synthase, promoting glycogenesis. But the ligand here is glucagon. It is more on the release of glucose from glycogen.

We can see here, the communication. The different signals and production of cAMP, take note that cAMP-dependent protein kinase once it is activated by cAMP, there are a lot of effects. You can even stimulate protein synthesis, calcium transport and DNA synthesis. Glycogen breakdown and lipid breakdown. Microtubule secretion. PHOSPHOINOSITIDES

Second messengers derived from phosphorylation of inositol by PI kinase

1. Phosphatidyl inositol (PI) 2. PI 4-phosphate (PIP) 3. PI 4,5-Biphosphate (PIP2) 4. Inositol 1,4,5-triphosphate (PIP3)

Phospholipid Structure

Sugar Alcohol (glycerol) R1 - Saturated FA R2 – Unsaturated FA Phosphate X – Alcohol (e.g. Choline, Inositol, etc)

It was mentioned earlier that once you have the ligand-receptor interaction, you activate an enzyme. In the cAMP pathway, what is the enzyme acticated? Adenyl cyclase. In the PHOSPHOINOSIDTIDES PATHWAY, the enzyme activated is phospholipase C. And this enzyme, remember in lipid metabolism, what are the types of phospholipase?

Phospholipase A1, A2, C, B (each one has its own bond to cleave)

So where does phospholipase C work? Generating inositol IP3 and di acylglycerol

TWO BRANCHES of INOSITOL PHOSPHOLIPID PATHWAY

Activated Phospholipase C-ß cleaves PIP2 to generate IP3 and DAG(diacylglycerol)

IP3 releases Ca++ from ER


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DAG together with bound Ca++ activates C-Kinase C → Kinase phosphorylates cell proteins

Phosphoinositol (IP3)

Once activated, it will cause release of Calcium from Endoplasmic Reticulum

1,2-Diacylglycerol (DAG) It will bind to Calcium to activate C-Kinase enzyme

Remember phosphatidyl inositol phospholipid, it has glycerol, with carbon, 2 Fatty acids, diacylglycerol with the phosphate and the alcohol group which is inositol.

The glycerol with the fatty acid and the phosphate here and the inositol. Phospholipase C acts on this part and you produce a diacylglycerol (DAG), and you remove the phosphate and inositol group. So you have DAG and the inositol phosphate. Phosphorylate it further and it becomes inositol triphosphate. So these are your second messengers. IP3 (Inositol Phosphate) and DAG (diacylglycerol). And you have the same receptor; G-protein coupled receptor → TRIMERIC G. but instead of adenyl cyclase, you activate enzyme phospholipase C. So what is the effect of the second messenger?

DAG inactivate C kinase enzyme Inositol phosphate causes the release of Calcium from ER Ca is also considered a second messenger

Above shows release of Calcium from ER to cytoplasm. So once it is released into cytoplasm, being a second messenger, it relays the message. Ca now interacts with calmodulin. Calmodulin needs Ca to be functional. Ca binds with calmodulin, then you have the Active Ca-calmodulin complex and it activates now Calmodulin-dependent protein kinase. So you will see the response there; phosphorylation of other proteins. You have the signal here outside then a cascade of reactions; production of second messenger IP3 which will release Ca, then Ca binds with calmodulin. Activated calmodulin now phosphorylates other proteins. SIGNALING by RECEPTORS TYROSINE KINASES (RTK) and RAS (smaller GTPase protein)

LIGANDS → soluble or membrane-bound protein hormones NDGF, PDGF, FGF,EGF, insulin (hydrophilic) Binding stimulates the receptor’s intrinsic protein kinase

activity Functions:

cell proliferation, differentiation, cell survival and metabolism

RECEPTOR TYROSINE KINASE (RTK)

RAS – the GTPase monomeric protein that transduce signals from RTK

ACTIVE/ON – when bound to GTP INACTIVE/OFF – when bound to GDP Not directly linked to receptor RTK

KEY LINKS of RAS to RTK

GRB2 – adapter protein for receptor SH2 domain- binds to phosphotyrosine residue in

activated receptor SH3 domains - bind to and activate Sos


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Sos – functions as GEF(guanine nucleotide exchange protein) converts GDP-Ras to GTP-Ras

CYCLING of RAS between ACTIVE and INACTIVE FORMS

1. Guanine Nucleotide Exchange Factor (GEF) facilitates dissociation of Ras from GDP

2. GTP binds while GEF dissociates yielding active Ras*GTP 3. Hydrolysis of bound GTP to regenerate inactive Ras*GDP

GEF = Guanine nucleotide Exchange factor GAP = GTPase activating protein

So you have here the GEF and the GAP. GEF promotes the activation of Ras. GAP is needed for inactivation of Ras. ACTIVATION of RAS following BINDING of LIGAND to RTK

1. Binding of ligand causes dimerization and autophosphorylation of tyrosine residues

2. Binding GRB2 and Sos couples receptor to inactive Ras 3. SOS promotes dissociation of GDP from Ras 4. GTP binds and SOS dissociates from active Ras

GRB2 = growth factor receptor binding protein 2 SOS = son of sevenless

MAP KINASES

Mitogen activated protein (MAP) kinases are serine/threonine-specific protein kinases that respond to extracellular stimuli

mitogens, osmotic stress, heat shock proinflammatory cytokines

regulate various cellular activities, such as gene expression, mitosis, differentiation,

proliferation, and cell survival/apoptosis


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SIGNALING by MAP KINASE PATHWAY

1. MAP KINASE – serine/threonine kinase 2. Translocates or enters into nucleus to phosphorylate

proteins involved in transcription It is because Ras is still in the cytoplasm For this signaling pathway you need to

stimulate gene expression in nucleus 3. Activation of MAP kinase is induced by activated Ras 4. Other proteins involved:

Raf – serine/threonine kinase MEK- a dual-specificity protein kinase

MEK = “MAP kinase kinase and ERK kinase”

CASCADE of PROTEIN KINASES

1. Activated Ras binds to N-terminal of Raf 2. Raf binds to and phosphorylates MEK 3. MEK phosphorylates and activates MAP kinase 4. MAP kinase phosphorylates nuclear transcription factors

mediating cellular responses then translation (produce protein)

SIGNALING from PLASMA MEMBRANE to NUCLEUS

CRE ( cAmp-response element) cis-acting DNA sequence in genes regulated by cAMP

CREB (CRE-binding protein) a transcription factor to which CRE binds

CBP/300 a co-activator allowing CREB to stimulate

transcription CREB links cAMP to TRANSCRIPTION

1. cAMP activates cAmp-dependent protein kinase (cAPK) 2. cAPK translocates to nucleus and phosphorylates CREB

Similar to MAP Kinase 3. CREB interacts with CBP/300 4. CREB-CBP/300 complex binds to and activates transcription of

target genes

MAP KINASES REGULATE TRANSCRIPTION

MAP kinase is activated via RTK-Ras pathway Translocates to the nucleus and phosphorylates

activators and repressors of transcription


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NF-kB NF-κB (nuclear factor kappa-light-chain-enhancer of

activated B cells) is a protein complex that controls the transcription of DNA

Why is it called NF-Kappa beta? The B cells are included. Kapag nabasa ang B cells, mainly, signalling

pathways are involved in the immune system. The B cell. The antibodies.

Eventually you will end up with the transmission of DNA, mainly that pertains to the production of antibodies because antibodies are proteins.

NF-κB is found in almost all animal cell types and is involved in cellular responses to stimuli such as stress, cytokines, free radicals, ultraviolet irradiation, oxidized LDL, and bacterial or viral antigens

NF-κB plays a key role in regulating the immune response to infection (kappa light chains are critical components of immunoglobulins)

Incorrect regulation of NF-κB has been linked to cancer, inflammatory and autoimmune diseases, septic shock, viral infection, and improper immune development

NF-kB TRANSCRIPTION FACTOR

A heterodimer Magkapartner. Hetero means they are different because one sub-unit is 90 kilo Dalton and the other one is 65 kilodalton (p50 and p65)

In resting cells, found in cytoplasm bound to an inhibitor I-kß So it is not located in the nucleus immediately. And it is being held and bound to an inhibitor known as INHIBITOR KAPPA BETA. Bale parang may nakahawak sa kaniya kaya nasa cytoplasm lang siya. At ang humahawak sa kanya ay si inhibitor kappa beta.

In response to an extracellular signal, this inhibitor kappa beta is phosphorylated and degraded. When the inhibitor kappa beta gets inhibited,

NF kappa beta will now be relased because it is no longer held in place by inhibitor kappa beta. So once released from the inhibition of this I-kB, NF kappa beta translocates into the nucleus, binds to DNA and regulates transcription. This is a controlled pathway.

But if you have the signal, it will cause phosphorylation of the inhibitor kappa beta which will result to degradation of inhibitor kappa beta release and transfer of NF kappa beta into the nucleus.

NF-kß translocates to nucleus and binds to DNA and regulates transcription

Given that this is a signal, what is a possible signal for NF kappa beta?

There are infection (bacterial/viral), free radicals, reactive oxygen species, or mitogens.

Eto muna, originally in the cytoplasm. This is the heterodimer NF kappa beta being held by inhibitor kappa beta. So kung meron ka ng signal, this inhibitor kappa beta will be phosphorylated and the process is known as UBIQUITINATION. It is one way of degrading protein. If this inhibitor kappa beta is now degraded, NF kappa beta will be free and it will now translocate, going inside the nucleus that will cause expression of the genes. So there will be transcription and eventually translation. So if sa immune system yan, there will be production of antibodies whose action is targeted to this infection. You increase the immune response against that signal because there is infection.

P50 p65 NF kappa beta, inhibitor kappa beta, stress, bacterial, viral incfections, cytokines, phosphorylation of the inhibitor kappa beta. So una, maactivate muna ang inhibitor kappa beta kinase. If the kinase is activated, IPB will be phosphorylated. If it is phosphorylated, it will be degraded; and the p50 & p65 will now translocate here causing gene expression.

There is activation of you kappa beta kinase, phosphorylation, degradation, NF kappa beta becomes free then it enters the nucleus; and then expression. You have now the production of proteins.


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So if it is Immunoglobulin G, yun ang naproduce mo, immunoglobulin G directed against infection.

GLUCOCORTICOIDS

For the treatment of inflammatory and immune diseases Inhibition of NF-Kappa beta by glucocorticoids

/Mechanisms: 1. Glucocorticoids increase IкB mRNA, which leads to

an increase IкB protein and more efficient sequestration of NF- кB in the cytoplasm

So if you have numerous inhibitor kappa beta NF-kB is sequestered in the cytoplasm. So you cannot produce the antibodies. If that is autoimmune, you decrease the production of antibodies, destroyed on your own tissue.

2. The glucocorticoid receptor competes with NF- кB for binding with coactivators

So inside the nucleus, there is the presence of DNA, co-activator and NF kappa beta. Glucocorticoids displaces NF kappa beta. So if there is no NF-kB, no gene expression.

3. The glucocorticoid receptor directly binds to the p65 subunit of NF- кB and inhibits its activation

Remember that you have the p50 and the p65. So pwedeng mag-attach ang steroids (glucocorticoids) sa NF-kB, inhibiting its activation.

JAK-STAT SIGNALLING PATHWAY JAK – Janus Kinase STAT – Signal transducer and activators of Transcription The JAK-STAT pathway plays a critical role in the

signalling of a wide array of cytokines and growth factors leading to proliferation, growth, hematopoiesis,immune response

JAKs, which have tyrosine kinase activity, bind to some cell surface cytokine receptors, similar to RTK

The binding of the ligand to the receptor triggers activation of JAKs.

With increased kinase activity, they phosphorylate tyrosine residues on the receptor and create sites for interaction with proteins that contain phosphotyrosine-binding SH2 domains

STATs possessing SH2 domains capable of binding these phosphotyrosine residues are recruited to the receptors, and are themselves tyrosine-phosphorylated by JAKs

So saka palang sila mag-aattach upon binding of the ligand. So the same. Phosphorylation by JAK.

These phosphotyrosines then act as binding sites for SH2 domains of other STATs, mediating their dimerization

Different STATs form hetero- or homodimers Activated STAT dimers accumulate in the cell nucleus and

activate transcription of their target genes

So again: Ligand phosphorylating your JAK. Then recruitment of STAT. Phosphorylation also of the STAT. Dimerization of the STAT. And translocation to the nucleus. So 3 na ang magtratranslocate sa nucleus.

1. MAP 2. CATK 3. STAT dimer 4. Even the NF kB is entering the nucleus.

What is the receptor for insulin? RTK, RAS

CAMP SYSTEM

Phsophodiesterase increases the level of cAMP. If we will enter the cell, there are several reactions occurring. If you have the cAMP activating the kinase, kinase enzyme

works on the different pathways not only gene expression. Binding of ligand G protein activation enzyme activation (adenylyl cyclase) production of cAMP from ATP phosphorylation of protein kinase the active protein kinase phosphorylates your glycogen phosphorylase GLYCOGENOLYSIS in addition, you already have your glucose. Activation of glycogen phosphorylase and inhibition of

glycogen synthase. So this is GLYCOGENESIS.


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Protein Kinase A will phosphorylate CREB. When CREB is phosphorylated, it binds with co-activator CDP300 and it interacts with cAMP response element (cis active DNA element).

CREB is the binding protein for CRE element. And then of course, expression, production of RNA,

transcription and translation PHOSPHATIDYL INOSITOL PATHWAY

Same. What is the receptor? G-protein What kind of G-protein? Trimeric G-protein Binding of the ligand. Once the G protein is activcated, it activates what enzyme?

Phospholipase C beta. It acts on phosphotidyl inositol, producing diacylglycerol plus

inositol triphosphate. What is the effect of Inositol Triphosphate? Release of

calcium from the endoplasmic reticulum And what is the effect of calcium? Another second

messenger. This is your second messenger, it binds with Calmodulin. And then once activated, calmodulin has other effects.

How about diacylglycerol? It activates the protein C kinase enzyme, phosphorylating also other proteins.

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Again, what is signal transduction? Converting a signal into a cellular response. So this is your trimeric G-protein

RTK RAS pathway Receptor Tyrosine Kinase So you have the ligand. An example is growth factor. You have the intermediate protein because the monomer

GTPase is not directly bound with the receptor.

Unlike in this one, the trimeric G protein is directly bound with the receptor.

But in the RTK RAS, there are adaptor proteins, the SOS and GRTP .

So once RAS is activated, RAP, MEK and activation of MAP, and

translocation of MAP kinase, phosphorylation of CREB and then activating gene transciption.

So pag tiningnan niyo yung cell, marami pang pathways. Eto lang yung mga namention natin

G protein RTK Jak stat NF Kappa pathway (kasi pwede natin maintegrate

ang signals)

“Having a rough day? Place your hand over your Heart

Feel that? That’s called PURPOSE.

You’re alive for a reason. DON’T GIVE UP.”

“The Lord will fight for you; you need only to be still.”

Exodus 14:14

GOD BLESS YOU, FUTURE MD

[BiochemB] Signal Transduction - Dr. Viliran (Bernabe and Dela Rosa).pdf

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