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Cell Bio 2382B > Cell Signalling > Flashcards

Cell Signalling Flashcards

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Biology 101 flashcards
1
Q

Signal Transduction

A
  • conversion of one signal into another

- uses growth factors, cytokines, hormones

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2
Q

Elements of Cell Signalling

A

1) Signal or Signalling Molecules – ligand
2) Receptors – cell-surface or intracellular
3) Intracellular Signalling and Effector Proteins
4) Secondary Messengers – amplify signal

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3
Q

Nuclear-Receptor Superfamily

A
  • intracellular receptor = interact w/ hydrophobic proteins
  • estrogen, progesterone, glucocorticoid, thyroxine, retinoic acid receptors
  • all receptors have –> ligand and DNA binding domain and variable region
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4
Q

Gene Activation by Nuclear Receptor

A

no glucocorticoid –> inhibitor (Hsp90) bind to ligand binding domain

glucocorticoid –> inhibitor released from LBD

  • glucocorticoid receptor moves into nucleus
  • bind to promoter elements in DNA
  • activation domain brings TF’s
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5
Q

Forms of Intracellular Signalling

A

Endocrine Signalling
- tissue produce ligand + hormone secretion DISTANT

Paracrine Signalling
- cell produce ligand + acts on ADJACENT cell

Autocrine Signalling
- cell produce ligand + it’s receptor = self-stimulate

Signalling by PM
- cell produce TM protein + interact with adjacent cell receptor

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6
Q

Signalling by Cell-Surface Receptors

A

1) synthesis + release of signalling molecule
2) bind to specific receptor = conformation change
3) intracellular signal-transduction pathways
4) short term cellular responses
- cell metabolism/function/movement
5) long term cellular responses
- gene expression/development
5) terminate cellular responses (feedback)

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7
Q

Dissociation Constant

A
  • measure of affinity of a receptor and ligand
  • ligand concentration to bind 50% cell receptor
  • lower Kd = lower ligand concentration = high affinity

Kd= [R][L]/[RL]

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8
Q

Functional Expression Assay

A

Identify cDNA encoding cell surface receptors

  • culture cells do not express receptor for ligand X
  • transfect w/ cDNA library + screen cellular phenotype
  • identify added cDNA by PCR ==> sequencing
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9
Q

Regulation of Protein Activity

A

Kinase
- activated by signalling –> add phosphate = ACTIVE
Phosphatase
- activated by signalling –> lose phosphate = INACTIVE

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10
Q

G-Protein Coupled Receptor System

A
  • a receptor has 7 membrane-spanning domain
  • a coupled trimeric G protein
  • a membrane-bound effector protein
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11
Q

G-Protein Complex

A

Trimeric G Protein

  • Gα – lipid anchored at cytoplasmic face (GDP/GTP)
  • Gγ – lipid anchored at cytoplasmic face
  • Gβ – linked to Gγ
  • transmit signal from G-protein coupled receptor to effector proteins
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12
Q

G-Protein Coupled Receptor Pathway

A

1) ligand bind to GPCR
2) recruit Gα subunit + trimeric complex
3) conformational change – dissociate GDP
4) bind GTP to Gα
5) conformational change – dissociate receptor + Gβγ
6) Gα binds + activate effector protein
7) GTP hydrolysis = Gα dissociate from effector and bind to Gβγ

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13
Q

FRET and Trimeric Complex

A

Inactive Receptor + Trimeric Complex
- excite CFP (Gα) release wavelength excite YFP (Gβγ)

ADD LIGAND…

Active Receptor + Gβγ + Gα

  • excite CFP (Gα) release wavelength = cyan
  • no interaction
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14
Q

Effector Proteins

A

Adenylyl cyclase –> 2nd messenger = cAMP

Phospholipase C –> 2nd messenger = IP3 or DAG

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15
Q

Activation of Muscarinic Acetylcholine Receptor

A
  • acetylcholine bind to its receptor
  • opening of K+ channel and cell polarization
  • Gβγ subunit activates effector protein (K+ channel)
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16
Q

Regulation of Adenylyl Cyclase

A

Stimulatory Hormones (epinephrine, glucagon)

  • binds to receptor –> stimulatory G protein complex
  • activate adenylyl cyclase = form cAMP

Inhibitory Hormones (PGE1 and adenosine)

  • binds to receptor –> inhibitory G protein complex
  • inhibit adenylyl cyclase = no cAMP
17
Q

Cholera Toxin

A

Inappropriate activation of adenylyl cyclase

  • toxin enters via ganglioside receptor in small intestine
  • toxin maintain in active state
  • mass activation of adenylyl cyclase
  • mass increase in cAMP
  • hyperactive CFTR ion channel
  • Cl- pumped out AND Na+ and H2O follows = diarrhea
18
Q

Pertussis Toxin

A

Whooping Cough

  • toxin enter ciliated epithelial cells in lungs
  • toxin inhibits inhibitor
  • mass activation of adenylyl cyclase
  • mass increase in cAMP
  • hyperactive CFTR ion channel
  • Cl- pumped out AND Na+ and H2O follows = mucous
19
Q

Intracellular Second Messengers

A

cAMP – activates protein kinase A
cGMP – activates protein kinase G
DAG – activates protein kinase C
IP3 – opens Ca2+ channels in ER

20
Q

Protein Kinase A (PKA) Activation

A

cAMP binds to regulatory subunits

  • binding 1st cAMP to CNB-B lowers Kd for binding of 2nd cAMP to CNB-A
  • catalytic domain separates after binding
21
Q

Regulation of Glycogen Metabolism

- high cAMP levels = active protein kinase A

A

Activating phosphorylation
- active glycogen enzymes = glycogen –> glucose

Inhibitory Phosphorylation

  • inhibit glycogen synthesis = NO glucose –> glycogen
  • inhibit phosphoprotein phosphatase
  • — activate inhibitor = inactive (phosphorylated)
22
Q

Regulation of Glycogen Metabolism

- low cAMP levels = active protein kinase A

A

Inhibitory Phosphorylation
- inactive glycogen enzymes = NO glycogen –> glucose

Activating Phosphorylation
- active glycogen synthesis

23
Q

Activation of Gene Transcription by G-Protein Coupled Receptor

A
  • genes regulated by protein kinase A have specific nucleotide sequence = cAMP response element (CRE)
  • activation of CRE-binding protein’s TFs by phosphorylation
24
Q

CRE-Binding Protein Signalling Pathway

A
  • G-protein activation –> adenylyl cyclase activated
  • increase cAMP levels –> activate protein kinase A
  • catalytic subunits of PKA translocate to nucleus
  • phosphorylate + activate CRE-binding TF
  • associates with co-activator CBP/P300
  • bind to CRE = activate transcription
25
Q

Phospholipase C

A
  • effector protein

- cleaves PIP2 into DAG and IP3

26
Q

IP3/DAG Pathway

A
  • GPCR + trimeric complex dissociate
  • Gα bind Phospholipase C –> cleaves PIP2 = DAG + IP3
  • IP3 bind to Ca2+ channel at ER = release Ca2+
  • Ca2+ binds to protein kinase C
  • protein kinase C binds DAG
27
Q

Vasodilation

A
  • acetylcholine –> acetylcholine GPCR
  • phospholipase C –> IP3 –> Ca2+ and binds calmodulin
  • NO synthase –> NO (diffuse to smooth muscle)
  • NO receptor converts GTP to cGMP
  • cGMP binds protein kinase G
  • relax muscle cell
28
Q

Viagra

A
  • phosphodiesterase inhibitor
  • inhibits the PDE that hydrolyzes cGMP to GMP
  • more cGMP for PKG = relax muscle for blood to fill

Cell Bio 2382B (12 decks)

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