signal transduction 4 Flashcards by Sumit Puri

DAG and PIP3

plasma membrane second messenger

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camp cgmp

h20 soluble second messneger

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ion second messenger

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ips

water soluble second messneger

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arachnidoic acid

PM associated second messneger

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tf Ca can be made and destroyed

F cant

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Ca2+ ——- in the particular compartment of the cell is the signal detected by the next member in the signaling cascade.

Ca2+ concentration in the particular compartment of the cell is the signal detected by the next member in the signaling cascade.

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tf cell quiet

When Ca2+ concentration increases (10-6 M or greater

When cytoplasmic Ca2+ concentration is low (10-7 M)

When Ca2+ concentration increases (10-6 M or greater), sensor molecules detect the rise and activate specific responses.

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Cell activation depends on a —— between calcium—- and calcium- — mechanisms.

Cell activation depends on a balance between calcium-OFF and calcium-ON mechanisms.

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2 ways Ca off mechanism remove Ca

pumping it from the cell

or back into internal stores

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Na+ /Ca2+ exchanger (NCX)

or antiporter Ca2+ -ATPase (PMCA)

Plasma membrane proteins that are calcium pumps

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 Sarco/endoplasmic reticulum Ca2+-ATPase (SERCA)

Intracellular calcium pumps

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Low affinity

High transport rate

Na+ / Ca2+ Exchanger (NCX)

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High affinity Low transport rate

Ca2+-ATPase (PMCA)

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SERCA

Ca in with ATP breakage

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TF CA binding proteins only exist in the SER

F in SER and cytoplasm(buffer action)

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Calcium-ON mechanisms add Ca2+ to the cytoplasm from ——- sources and —– stores

Calcium-ON mechanisms add Ca2+ to the cytoplasm from extracellular sources and internal stores

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(favored by large electrochemical gradient).

Calcium on mechanism that add Ca to cytoplasm

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Ligand-gated ion channel receptors

cation selective

let Ca into cytoplasm

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Voltage-gated channels

(action-potential responsive)

let Ca into cytoplasm

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universal Intracellular calcium channels

1,4,5-Inositol trisphosphate receptors (IP3R)

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skeletal and cardiac muscle Intracellular calcium channels

Ryanodine receptors (RyR)

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AP or

voltage gated Ca channel

allow Ca into cell

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Ryanodine Receptor (RyR)

and 1,4,5-Inositol Trisphosphate Receptor (IP3R)

both need to be triggered by Ca to release Ca from their compartments

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Various ------ -binding proteins act as molecular ----- for detecting increased cellular concentration of ----- .

Various calcium-binding proteins act as molecular sensors for detecting increased cellular concentration of Ca2+ .

Activated sensors stimulate a variety of ----- proteins that regulate specific cellular functions.

Activated sensors stimulate a variety of downstream proteins that regulate specific cellular functions.

found in all cells where it mediates many regulatory pathways.

Calmodulin (CaM)

restricted to skeletal and cardiac muscle where it regulates contraction by controlling actin-myosin interaction

TnC

Two major Ca2+ sensors are

Two major Ca2+ sensors are tropinin C and calmodulin.

loops bind Ca

in Calmoduline and middle alpha helix stretches

tf Ca2+/CaM-Dependent Protein Kinase is not at all active when it doesnt have Ca 2+ CaM attached to it.

F it is 80% active although inh portion of it is free and open

Ca2+/CaM-Dependent Protein Kinase (CaM-Kinase II)

totally inactive when phospatase strips off PO4 from it3

bind inh domain of Ca2+/CaM-Dependent Protein Kinase (CaM-Kinase II)

Ca 2+/CaM

activation of Ca2+/CaM-Dependent Protein Kinase (CaM-Kinase II)

prompts autophos and Ca2+/CaM-Dependent Protein Kinase (CaM-Kinase II) is fully active

Tf 1st Ca is release then CaM is released from Ca2+/CaM-Dependent Protein Kinase when it is fully active

T renders it partially active

adenylate cyclase

converts ATP to cAMP

AC occurs at

G-protein-coupled receptor act. by

Camp

cat domain of AC

b/n helix 6 and 7

TF both N and C terminal of AC exist intercellularly

has 12 total alpha helix( transmembrane)

when ligand binds GPCR

G protein binds it

bind of g protein to GPCR

triggers GTP exchange on alpha subunit and it subsequently binds AC (PM)

Camp

binds reg. subunit of pka and dissociates catalytic subunit from regulatory

catalytis subunit of pKa

phos CREB and alters gene expression

gpcr1;gpcr2

g protein stim; g protein inh +camp;- camp

Cholera toxin

has enzymatic activity that int with NAD in cyt.

Ox Nad when triggered by Cholera toxin will

transfer adp ribose on Arg on Gs subunit of G protein(cant longer use ATPase activity)

transfer of ADP ribose to ARg on Gs

inc camp by promoting irreversible binding of alpha subunit to AC(cant use Gtpase activity)

cholera

prolonged opening of Cl channels and inc. Pka activity

tf in cholera there is minimum loss of Na and water in intestines

F excessive

pertusssis toxin

transfer ADP ribose to Cys on alpha subunit of Gi Gi cant bing AC and cant inh

inc Pka and camp exist in

cholera and pertussis

High insulin; low glucose (seizures) High histamine; low pressure (shock)

Pertussis

TF hormone levels not affected in pertussis

F affected

termination of camp

pde converts it to 5' amp

converts GTP to cGMP

bind ssoluble GC on a heme

binds to membrane ass GC

ANF

cGMP act

PKG

cGMP term to

5 gmp by cGMP Phosphodiesterase

Pi PE PC

polar head group of phosphpholipid

PIP2

Major Substrate for Producing Second Messengers

Phosphoinositide-4-Kinase

convert PI to PIP

PIP converted to PIP2 by

Phosphoinositide-5-Kinase

Activator of Ca2+ release from endoplasmic reticulum

IP3

phospholipase C

breaks PIP2 into DAG and IP3

DAG

Membrane bound

Activator of protein kinase C (PKC)

DAG

phsopholipase D

breaks PC into phosphatidic acid and choline (1st step of DAG generation)

PAP

break phosphatidic acid ito DAG and PO4 | (2nd step)

IP3 act

ip3sensitive channels to let out Ca Ca bind protein kinase C which binds DAG (membrane) which phos substrates

Precursor for production of eicosanoids

Arachidonic acid (AA) –

phosphlipase A2

breaks PIP2 into AA(membrane bound) and

only has PO4 on 1 position

PIP

PO4 on 4 position

PIP2

po4 on 1,4,5 position

PIP3

Activator of kinases recruited to membrane

PI 3 kinase

puts po4 on 3 position converts PIP2 to PIP3

tf phosphatase can convert PIP3 to PIP2 to PIP1 to PI

exist in cytoplasm

camp cgmp ip3

membrane

DAG AA PIP3

tf IP3 and PIP3 use PIP2 as a source

AA and DAG

use PC and PE as a source

uses PI PIP PIP2 as sources

tf dag can use PIP2 as source

ATP;GTP as source

camp; cgmp

Forms eicosanoids

Activates PKB, PDK1

PIP3

act. pkg;pkc

cGMP;DAG

act pka

camp

release Ca from ER

IP3

effector AC ; GC

camp; cgmp

Pla2 is effector enzyme for

pi 3k effector enzyme for

PIP3

PLC is effector nzyme for

IP3 and DAG

PLD/PAP effector enzyme fore

DAG

GC effector enzyme for

cGMP