Cell Communication

1. Cell Communication

2. How would you handle the following: • You would like to tell your friend across the room about a party that is happening tonight, but you don’t want to disrupt your teacher or let anyone else in class know about it. • How could you get this message to them before class is over? This would be considered short/local distance, specific communication EX: pass a note with your friend’s name on it

3. A teacher wants to remind everyone in the class that they have a test on Friday. • What would be the most efficient way to contact every student? This would be considered short/local distance, broadcast communication EX: write a reminder on the board

4. You are a college counselor at a high school and you need to give an application to all the seniors who are applying for early admission. • How can you notify each of these people? This would be considered long distance, specific communication EX: make an announcement during an assembly, asking all the seniors applying for early admission to stay after for a quick meeting.

5. You are on the yearbook committee and would like to organize a fundraising car wash event. • How could you get the word out to the community, so that there is a good turnout? This would be considered long distance, broadcast communication EX: put an advertisement in the local paper

6. What are some ways that organisms use specific communication (long distance and short distance)? sounds colors pheromones

7. How might cells communicate?

8. Evolution of Cell Signaling • Began in ancient prokaryotes & single celled eukaryotes. • Critical in the microbial world: • Bacteria will secrete chemicals signals to share information about nutrient availability. • Starving cells secrete a chemical that will stimulate neighboring cells to aggregate. The cells form thick-walled spores allowing the cells to survive until the environment improves.

9. Quorum Sensing: How bacteria communicate Quorum sensing: allows bacterial populations to coordinate their behaviors so they can carry out activities that are only productive when performed by a given number of cells in synchrony. Watch Bonnie Bassler-TEDTALK

10. Plasma membranes Plasmodesmata between plant cells Gap junctions between animal cells Figure 11.3 (a) Cell junctions. Both animals and plants have cell junctions that allow molecules to pass readily between adjacent cells without crossing plasma membranes. • Animal and plant cells • Have cell junctions that directly connect the cytoplasm of adjacent cells

11. (b) Cell-cell recognition. Two cells in an animal may communicate by interaction between molecules protruding from their surfaces. • In local signaling, animal cells • May communicate via direct contact • EX: immune system & embryonic development

12. Cell to Cell Communication- (no distance; passing a note) Immune system I got the message, now I know the shape of the invader & will pass this on

13. Cell to Cell Communication (no distance; passing a note)

14. Cell to Cell Communication (short distance…on the board message) Neurons Local regulator = neurotransmitters

15. Exchange of mating factors. Each cell type secretes a mating factor that binds to receptors on the other cell type. factor 3 1 2 Receptor a  factor Yeast cell, mating type a Yeast cell, mating type Mating. Binding of the factors to     receptors induces changes      in the cells that     lead to their     fusion.  a New a/ cell. The nucleus of the fused cell includes all the genes from the a and a cells. a/ Figure 11.2 • Yeast cells • Identify their mates by cell signaling

16. Local signaling Target cell Electrical signal along nerve cell triggers release of neurotransmitter Neurotransmitter diffuses acrosssynapse Secretory vesicle Local regulator diffuses through extracellular fluid Target cell is stimulated (b) Synaptic signaling. A nerve cell releases neurotransmitter molecules into a synapse, stimulating the target cell. (a) Paracrine signaling. A secreting cell acts on nearby target cells by discharging molecules of a local regulator (a growth factor, for example) into the extracellular fluid. • In other cases, animal cells • Communicate using local regulators Neurotransmitters Growth factors

17. Cell to Cell Communication (long distance; hit a lot of cells…advertisement in local paper) Message gets sent to a lot of different cells. Some will act on it and some won’t. The ones that do act may not all act in the same way.

18. Long-distance signaling Blood vessel Endocrine cell Hormone travels in bloodstream to target cells Target cell (c) Hormonal signaling. Specialized endocrine cells secrete hormones into body fluids, often the blood. Hormones may reach virtually all body cells. • In long-distance signaling • Both plants and animals use hormones Hormonal signaling AKA: endocrine signaling

19. Plant hormones • Sometimes travel through vessels but more often travel through the air as gas (ethylene).

20. What are theses types of signals? Are they short/local or long distance? Are they specific or general? Paracrine signaling Synaptic signaling Hormonal signaling Short/local & general Short/local and specific Long distance and general or specific

21. The Stages of Cell Signaling: A Preview • Earl W. Sutherland • Established that epinephrine causes glycogen breakdown without passing through the membrane. • Discovered how the hormone epinephrine acts on cells • Sutherland suggested that cells receiving signals went through three processes • Reception • Transduction • Response

22. Reception- target cells detection of a signaling molecule (ligand) that binds to a receptor protein, causing it to change shape Transduction-several steps where each molecule brings about a change in the next molecule Response occurs with the last molecule in the transduction pathway & triggers the cell’s response.

23. Transduction Pathway Project • RECEPTION: • G-Proteins • Tyrosine-kinase • Ion Channels • Intracellular • TRANSDUCTION: • Protein phosphorylation • Calcium Ions • Cyclic AMP • RESPONSE • Cytoplasmic & Nuclear • Fine tuning

24. Are the binding sites for the initial signal and is responsible for transmitting the signaling into or throughout the cell. -can be intracellular or extracellular -change shape when a ligand attaches Receptors EX: G-protein Like a light switch: in the “on” position, a connection is made with the energy source; in the “off” position, there is no driving energy.

25. Gate closed Signalmolecule(ligand) Ions Ligand-gated ion channel receptor Plasma Membrane Gate open Cellularresponse Gate close • A ligand-gated Ion channel receptors Like automatic double doors through which large crowds can flow or not flow, depending on if the doors are open or closed.

26. Disrupting the Communication Dopamine is a chemical in your brain that affects your emotions, movements and your sensations of pleasure and pain. Drugs, such as amphetamines and cocaine, cause buildup of dopamine, which leads to drug-induced psychosis or schizophrenia.

27. Other Type of Intracellular Receptors • Intracellular receptors • Are cytoplasmic or nuclear proteins • Signal molecules that are small or hydrophobic • And can readily cross the plasma membrane use these receptors Like undercover cops hidden in a crowd

28. Signal-binding sitea Signalmolecule Signal molecule Helix in the Membrane Tyr Tyr Tyr Tyr Tyrosines Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr Receptor tyrosinekinase proteins(inactive monomers) Dimer CYTOPLASM Activatedrelay proteins Cellularresponse 1 Tyr Tyr Tyr Tyr Tyr Tyr P P Tyr P Tyr Tyr Tyr Tyr P Tyr Tyr Tyr P P P Tyr Tyr Tyr Tyr Tyr P Tyr Tyr Tyr Cellularresponse 2 P P P Tyr Tyr P 6 ATP 6 ADP Activated tyrosine- kinase regions (unphosphorylated dimer) Fully activated receptor tyrosine-kinase (phosphorylated dimer) Inactiverelay proteins Figure 11.7 • Receptor tyrosine kinases (insulin uses these) Can trigger more than 1 signal transduction pathway -coordinates many aspects of cell growth & reproduction -abnormal tyrosine receptors (function w/o signal molecules) may contribute to some cancers. Kinase is an enzyme that catalyzes the transfer of phosphate groups Like a friend who brings together 2 people who otherwise don’t hang out (unless it’s with this friend); the 3 have a greater time whenever they are together.

29. Signal molecule A relay molecule activates protein kinase 1. Receptor Activated relay molecule 4 1 3 5 2 Inactive protein kinase 1 Active protein kinase 1 transfers a phosphate from ATP to an inactive molecule of protein kinase 2, thus activating this second kinase. Active protein kinase 1 Active protein kinase 2 then catalyzes the phos- phorylation (and activation) of protein kinase 3. Inactive protein kinase 2 ATP Phosphorylation cascade P Active protein kinase 2 ADP PP P i Enzymes called protein phosphatases (PP) catalyze the removal of the phosphate groups from the proteins, making them inactive and available for reuse. Inactive protein kinase 3 Finally, active protein kinase 3 phosphorylates a protein (pink) that brings about the cell’s response to the signal. ATP P ADP Active protein kinase 3 PP P i Inactive protein ATP P ADP Active protein Cellular response PP P  i SIGNAL TRANSDUCTION PATHWAYS • A phosphorylation cascade Like flipping the switch of a mechanical toy which goes full speed when it is turned on and is completely still when turned off.

30. Transduction Changing the chemical message outside the cell to a message inside the cell. Inactive until g-protein attaches Converts ATP into cAMP Has regulatory factors and catalytic factors cAMP attaches & breaks regulatory factors away & catalytic factors become energized with the help of ATP (phosphorylation) Response Activate phosphorylase to breakdown glycogen into glucose in muscle cells & sometimes in liver cells.

31. How long does it last? • The cAMP boost does not last without another surge of epinephrine. • If there is no epinephrine another enzyme, phosphodiesterase, converts cAMP to AMP. Like the trigger on a water gun, each time the trigger is pulled the reaction is immediate and temporary; cAMP is produced each time there is a cell signal stimulant (such as epinephrine) but the cAMP does not stay present long.

32. Microbes causing disease: Cholera: Vibrio cholerae Bacteria colonize the lining of the small intestine & produce a toxin Toxin is a protein that modifies a G-protein so it remains stuck in active mode, stimulating the adenylyl cyclase. Water flows out by osmosis High amounts of cAMP causes intenstinal cells to secrete large amounts of salts into intestines The G-protein regulates salt & water secretion Causing profuse diarrhea & eventually death if untreated Adenylyl cyclase is continuously making cAMP

33. Calcium Ions • Many signal molecules in animals induce responses by increasing the cytosolic concentration of the calcium ions (Ca2+). • Calcium is used as a second messenger • Even more often than cAMP Like drinking caffeinated drinks, if you sip the caffeinated drink over a long period all day, it will not cause a stimulant response, but if you increase the level of caffeine in the body quickly, it causes activity to increase.

34. Cellular Responses can be either short-term or long-term • Short-term: • Changes in cell shape • EX: lymphocyte pursuit of a bacterium • Movement of vesicles to the membrane • EX: glucose transport • Long-term: • Activation of transcription • EX: cause cell to start dividing, to secrete a signal for other local cells, to initiate apoptosis

35. The response of a particular cell to a signal depends on its particular collection of receptor proteins, relay proteins, and proteins needed to carry out the response. • Two cells that respond differently to the same signal differ in one or more of the proteins that handle and respond to the signal.

36. “Programmed cell death”= Apoptosis

37. Maintaining blood glucose levels. WHAT INSULIN DOES… Feedback inhibition (negative)

38. If you wanted to design a drug to maintain low blood sugar what are some approaches? • Design a compound • That blocks epinephrine receptor activation • That inhibits cAMP production in liver cells • To block G-protein activity in liver cells • That inhibits phosphorylase activity.

39. It’s time for Interactive Lessons In Biology http://ats.doit.wisc.edu/biology/lessons.htm