POGIL: Cell Communication

Cell Communication CHAPTER 11

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

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?

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

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

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

Reception

Transduction

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

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

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

G-Protein-Coupled Receptor

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)

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 _______________

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.

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.

Receptor Tyrosine Kinase

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

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

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

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

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 ________________

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

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

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

An Example of Cell Communication http://learn.genetics.utah.edu/content/begin/cells/cellcom/

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

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

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

Viagra inhibits cGMP breakdown

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 (________________, ________________)

Apoptosis of a human white blood cell Figure 11.19 Apoptosis of human white blood cells Left: Normal WBC Right: WBC undergoing apoptosis – shrinking and forming lobes (“blebs”)

Effect of apoptosis during paw development in the mouse Figure 11.21 Effect of apoptosis during paw development in the mouse