1. POGIL: Cell Communication

2. Cell Communication
CHAPTER 11

3. Do bacteria communicate?
Bonnie Bassler on How Bacteria “Talk”

4. Video Questions:
Why are scientists studying how bacteria (and not just human cells) communicate?
What is quorum sensing?
Describe how Vibrio fischeri use quorum sensing in squid.
According to Bonnie Bassler (Princeton University), what are scientists hoping to use as the next class of antibiotics?

5. Cell Signaling Animal cells communicate by:
_________________________ (gap junctions)
Secreting ______ regulators (growth factors, _____________________)
Long distance (___________)

6. Local/short distance; neurotransmitters move across a __________
_________________; hormones travel through bloodstream

7. 3 Stages of Cell Signaling:
____________________: Detection of a signal molecule (__________) coming from outside the cell
__________________: Convert signal to a form that can bring about a cellular response (often involves amplification)
__________________: Cellular response to the signal molecule

8. Reception

9. Transduction

10. Response If in the _________, the response activates genes
If in _____________, activates enzymes/proteins

11. 1. Reception
Binding between signal molecule (___________) + ________ is highly specific.
Types of Receptors:
Plasma membrane receptor
Bind _________________ ligands
____________receptors (cytoplasm, nucleus)
____________________ or small ligands
Eg. ______________ or ________________ (NO)
Ligand binds to receptor protein  protein changes ___________  initiates transduction signal

12. Plasma Membrane Receptors
G-Protein Coupled Receptor (GPCR)
Tyrosine Kinase
Ligand-Gated Ion Channels
Very widespread in animals/humans
_______________ that act as ____________________
Region on receptor ________ _________ and acts like a “_________” when signal molecule binds
Work with the help of a ____________________– binds to ______ (energy molecule similar to ATP)
Transfers ___ group from ATP to the amino acid _____________
Gates may _____ or ______to regulate flow of specific ions
(__________________)
___transmembrane segments in membrane
Activate _______________ cellular responses at once
Important in ________________ system
G protein + GTP activates _________  cell response
Abnormal RTKs are associated with many _______________
Some gated ion channels are controlled by ______________ signals instead of ligands. These are ________________-gated ion channels

13. G-Protein-Coupled Receptor

14. G-Protein-Coupled Receptor
G protein is a molecular ______.
Inactive/off when _____ is bound
Active/on when _____ is bound
G proteins work together with a receptor (GPCR)
G proteins work together with an enzyme (or other protein)

15. G-Protein-Coupled Receptor
_____________ molecule (ligand) binds to cytoplasm side of GPCR
Receptor is _________ and changes shape.
Cytoplasm side of the receptor then binds ________________ ____________, causing GTP to displace _______
This activates the _______________

16. G-Protein-Coupled Receptor
Activated G protein leaves the receptor and moves down the membrane to an __________________
Signaling molecule can __________many times
Activated enzyme changes ________ and triggers next step in cell response.

17. G-Protein-Coupled Receptor
Changes in G protein and enzyme are ______________.
G protein also acts a _____________ enzyme (hyrdolyzes bound GTP to GDP)
Everything resets and G protein can be used again.

18. Receptor Tyrosine Kinase

19. Receptor Tyrosine Kinase
Signal molecules (ligands) binds to both __________
Monomers come together and form a ___________ (=dimerization)

20. Receptor Tyrosine Kinase
Each tyrosine kinase adds a ____________ from _____ to the ______________ on the tails

21. Receptor Tyrosine Kinase
_______ proteins inside the cell bind to specific phosphorylated tyrosine, undergoes a shape change, and then triggers a _______________ pathway leading to a ______________________________.

22. Ligand-Gated Ion Channel
_________ binds to receptor (closed)  shape change  gate ________
The gate _________ when the ligand _______________
______ flow into the cell through open gate; activates cell in some way

23. 2. Transduction
Cascades of molecular interactions relay signals from __________ to _____________ molecules
Usually involve _________________________: enzymes that phosphorylate (transfer a ______________ group from _____ to a __________) and activate proteins at next level (turn signal ___)
Protein phosphatases: ______________ that remove ____________ groups and _________________ protein kinases (can turn signal _____)
Phosphorylation cascade: helps to ______________ and _____________ signal to allow a greater cellular ________________

25. Second Messengers
small, _________________ molecules/ions that can relay signal inside cell
Eg. cyclic AMP (__________), calcium ions (Ca2+), inositol triphosphate (IP3)
Once activated, initiate a ________________ cascade

26. cAMP cAMP = ______________________________
GPCR  adenylyl cyclase (convert ATP  cAMP)  activate protein kinase A

27. 3. Response
Regulate _____________ synthesis by turning on/off genes in ____________ (gene expression)
Regulate activity of ___________ (including enzymes) in ____________

28. An Example of Cell Communication

29. Signal Transduction Pathway Problems/Defects:
Examples:
Diabetes
Cholera
Autoimmune disease
Cancer
Neurotoxins, poisons, pesticides
Drugs (anesthetics, antihistamines, blood pressure meds)

30. Cholera
Toxin modifies G-protein involved in regulating salt & water secretion
G protein stuck in active form  intestinal cells secrete salts, water
Infected person develops profuse diarrhea and could die from loss of water and salts
Disease acquired by drinking contaminated water (w/human feces)
Bacteria (Vibrio cholerae) colonizes lining of small intestine and produces toxin

31. Viagra Used as treatment for erectile dysfunction
Inhibits hydrolysis of cGMP  GMP
Prolongs signal to relax smooth muscle in artery walls; increase blood flow to penis

32. Viagra inhibits cGMP breakdown

33. Apoptosis = _______________
Cell is dismantled and digested
Triggered by signals that activate ___________ of “suicide” proteins (caspase)
Why?
___________ neighboring cells from damage
Animal _________________ & maintenance
May be involved in some diseases (________________, ________________)

34. Apoptosis of a human white blood cell
Figure Apoptosis of human white blood cells
Left: Normal WBC
Right: WBC undergoing apoptosis – shrinking and forming lobes (“blebs”)

35. Effect of apoptosis during paw development in the mouse
Figure Effect of apoptosis during paw development in the mouse