G Protein-Coupled Receptor - ap
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Transcript G Protein-Coupled Receptor - ap
Cell Communication
Chapter 11 - Abridged
Cell-to-Cell Communication
Critical for multicellular organisms
Trillions of cells must communicate in order to
coordinate their activities
Recent research indicates: cancer results from
corrupted communication
Unimportant for the AP Exam
Crucial for understanding the breakthroughs in cancer
and genetics that are occurring almost monthly now
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Recent Nobel Prizes in Medicine
2001 – Hartwell, Hunt, &
Nurse – cyclin pathways and
cell cycle regulation (yeast)
2002 – Brenner, Sulston,
Horvitz – used C. elegans to
elucidate the mechanism of
apoptosis
2006 – Fire & Mello - used
C.elegans to discover the
pathway of RNA interference
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Simon Sez…
Signaling is a lot like the game “Simon Says…”
The signal is received: the game players hear: “Simon
says take a step forward”
The signal is transduced: players must decide whether
to step forward or not
The signal elicits a response: players step forward if the
command was preceded by “Simon says”
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3 Stages of Signaling
Thesis: external signals are received & converted to
responses within the cell
1. Reception
Signaling molecule binds to receptor protein = Shape Change
2. Transduction
Cascades of molecular interactions relay signals from
receptor proteins to target molecules in the cell
3. Response
Regulation of transcription or cytoplasmic activities
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1st form of signaling
Yeast (fungi) mating
Process:
1.Release mating factor
2.Receive complementary
factor
3.????
4.Response: grow toward
opp. Type
5.Nuclei fuse = genetic
recombination
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Overview of Cell Signaling
Slide 7 of 23
View Animation
11_06 SignalingOverview_A.swf
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Reception
Reception involves getting the signal to the correct
receiver
Only certain cells have the correct receptor = only
certain cells can receive the signal
Signaling molecule usually called ligand
receptor-ligand binding causes a conformational change
in the receptor molecule (remember induced fit?)
Conformational change = Activation of the receptor
molecule
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2 Types of Signal Receptors
1. Plasma Membrane Receptors
Hydrophilic or water-soluble ligands or signal molecules
G Protein-Coupled Receptors (GPCR)
Receptor Tyrosine Kinase (RTK)
Ion Channel Receptors
2. Intracellular Receptors
Hydrophobic or Nonpolar ligands
Carry out transduction by themselves
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View Animation
11_13SignalTransduction_A.swf
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G Protein-Coupled Receptor
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Receptor Tyrosine Kinase (RTK)
Amplification
Kinase = enzyme
for transfer of
phosphate group
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Ligand-Gated Ion Channel
Membrane receptor with a region
that acts as a “gate” when the receptor
changes shape.
When the signal molecule binds,
gate opens or closes
Important in the nervous system
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Intracellular
Receptor
Hydrophobic signal molecules
Testosterone
Most intracellular receptor
signals do the entire transduction
on their own
Testosterone behaving as a
transcription factor
-- controls which genes (DNA)
are transcribed into mRNA
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Transduction
Multistep Pathway
Transduction = shape change
Signal amplification
Signal Transduction Pathways often
involve a phosphorylation cascade
Molecule is phosphorylated = activated
Phosphate removed = deactivation
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Protein Kinases (PK)
-- enzymes that transfer
phosphate groups
Protein Phosphatases (PP)
-- enzymes that remove
phosphate groups
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Second Messengers
1st messenger = receptor
Only GPCR & RTK have 2nd messengers
Other important component of transduction pathways
Most components are enzymes or proteins
Small & polar
Calcium Ions & Cyclic AMP
Initiate a phosphorylation cascade
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Response
Response may occur in the cytoplasm or nucleus
2 Types of typical response:
1. Enzyme activity is regulated (turned on or off)
2. Synthesis of enzymes is regulated (promoted or inhibited)
Transcription Factors – control which genes are
transcribed (DNA RNA)
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Transcription
Factors
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GF = Growth
factor
RTK = Receptor
Tyrosine Kinase
Ras = G Protein
Associated with
tumor growth
Rho = G protein
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RTK = Receptor
Tyrosine Kinase
GPCR – G-protein
coupled receptor
PDK1 = Protein
dehydrogenase
kinase
Akt = Protein kinase
-- Involved in apoptosis
Apoptosis =
Programmed cell death
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Day 1 Complete
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