Lecture 5 & 6: Communication Flashcards by Glenn Shatford

What are the 3 mechanisms for local signaling?

1) Gap junction dependent communication
2) Contact dependent signals
3) Paracrine and autocrine

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Gap junctions are

channels that connect adjacent cells

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Where are gap junctions common

Heart, Smooth muscles and some neurons

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What proteins (and what structure) form the bridge between the cytoplasm of each cell

Connexin, quaternary structure

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Where does the cytoplasmic bridge come from

each cell will supply a connexon to the formation of a gap junction

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Hydrophobic or Hydrophilic channels forms within gap junctions

Hydrophilic

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What types of solutes are able to move freely from the cytoplasm of one cell to another

small solutes

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What is Contact-Dependent Signalling

A molecule (ligand) in the Extracellular matrix of one cell binds to a receptor in the membrane of the adjacent cell, or a component of the ECF surrounding the cell

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Contact- Dependent signalling is important to

the immune system, axon guidance and development

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Define local communication

A signaling molecule is secreted from a cell and binds to ligands either on the same cell (autocrine) or to other cells near by (paracrine)

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Paracrine causes what two things

smooth muscles to dilate

increases blood flow to binded area

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What are the three types of Long distance communication

1) Hormones
2) Neurotransmitters
3) Neurohormones

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What is the difference between endocrine and exocrine

Endocrine = substances secreted in to blood
Exocrine = substances secreted into a duct

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how does hormone communication work

Hormones are secreted by endocrine glands into the blood and then find a target cell with receptor cells

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Does every cell have a target for endocrine hormones

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Define neurotransmitters

Are released from a neuron into extracellular space, travels very small distances and binds to receptors on the next target cell

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Do Neurotransmitters or Endocrine system move faster

Neurotransmitters move much quicker

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Define neurohormones

basically a mix of both neurotransmitters and endocrine hormones. they are chemicals released by neurons into extracellular space that then travel into the blood in search of receptor-bearing target cells

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Except for gap junction signalling, Cell-to-cell signalling requires

1) Signal (Ligand)
2) Receptor
3) Way to transduce the message

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What does signal transduction pathway refer too

Converts one form of signal to another to another

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All cells have _____ pathways

some

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Why are pathways important

Can amplify the signals

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Define intracellular receptors

Are ligands usually lipophilic (Hydrophobic)
Able to diffuse through cell membranes and bind to receptors in the nucleus or cytosol
Often alter gene expression, slow but long- lasting
Ex; Cortisol, steroids

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Define Cell Membrane (EXTRACELLULAR) receptors

embedded in plasma membrane
ligands are lipophobic (hydrophilic)
bind to extracellular domains of receptors causing an activation of an intracellular signal transduction pathway
Ex; Epinephrine

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Intracellular signal receptors typically work with what

gene expression

What are the four main Cell membrane receptors?

1) Integrin Receptors 2) G-Protein-coupled Receptors 3) Receptor-enzyme (catalytic receptor) 4) Integrin receptor (catalytic receptor)

Define Integrin Receptors and what it is used for

Binding of the extracellular ligand leads to changes in the arrangement of the cytoskeleton or alters enzyme activity Cell movement, growth, wound healing

Define receptor Ion channels

Receptor is a transmembrane channel

What are the 3 things receptor (ion) channels are typically called?

1) Ligand-gated ion channels 2) Neurotransmitter-gated ion channels 3) Ionotropic receptors

In Receptor ion channels, the ligand is typically a what

neurotransmitter

Binding of neurotransmitters triggers the opening of what channel

receptor ion

What channels allow Ca++ into a cell

Receptor ion channels

Ca++ is an important _________ signal

intracellular

ionotropic receptors have to do with what

the movement of ions

Define receptor enzymes

Ligands binds to receptors and an intracellular enzyme is activated amplifying the signal significantly

Describe an In depth Example of receptor enzyme: Insulin Signaling

1) INsulin is released from the pancreas when blood sugar concentration is above set-point 2) The insulin binds to tyrosine kinase receptors and induces dimerization of receptors 3) Cytoplasmic tails of the receptor will then auto phosphorylate and transfer phosphate groups from ATP to tail of receptor 4) Phosphorylated receptor tails activate a kinase located in cytoplasm which then phosphorylates other substrates needed 5) End result is the addition of GLUT transported into plasma membrane which returns concentration to normal

G-Protein coupled Receptors (GPCRs) are

ligand binds to receptor and an intracellular enzyme is activated, could also trigger opening of ion channel

All GPCRs work to produce what

secondary messengers inside the cell

What are 3 important classic secondary messengers

cAMP cGMP Inositol triphosphate (IP3) Diacuglyceride (DAG)

What are 3 novel secondary messengers

a) Calcium b) Lipids c) Gases

What are secondary messengers also called

metabotropic receptors

GPCR consist of ___ transmembrane domains and ____ subunits

7; 3

When G-protein is active it is bound to _____

GTP

When G-protein is inactive its bound to ____

GDP

Describe the steps of GPCR Adenylyl Cyclase Signal Transduction and Amplification

1) Signal molecule binds to GPCR, which activates G protein 2) G protein turns on adenylyl cyclase (amplifier enzyme) 3) Adenylyl cyclase converts ATP to cyclic AMP (cAMP) 4) cAMP activates protein kinase A 5) Kinase A phosphorylates other proteins leading to a cellular response `

``` ABBREVIATIONS: What does the following stand for: PL-C DAG PK-C IP3 ER ```

``` PL-C = phospholipase C DAG = Diacylglyerol PK-C = Protein Kinase C IP3 = Inositol Trisphosphate ER = Endoplasmic Reticulum ```

Describe the steps in GPCR - Phospholipas3e C signal Transduction

1) Signal molecule binds to GPCR which activates a G protein 2) G protein activates phospholipase C (PL-C) which is an amplifier enzyme 3) PLC converts membrane phospholipids into DAG which remains in the membrane and IP3 which diffuses into the cytoplasm 4) DAG activates PKC, which phosphorylates proteins 5) IP3 causes releases of Ca2+ from organelles, creating a CA2+ signal

what 4 things do calcium binds to and what results from this

1) Binds to calmodulin = activation of other proteins 2) Binds to motor proteins and allows action 3) Binds to synaptic proteins to trigger exocytosis 4) Binds to ion channels to modulate their gating

What is now being recognized as secondary messengers?

Soluble gasses

NO is synthesized by what, and has a half-life of

NO-synthase, 2-30 seconds

What does NO activate

Guanylyl cyclase, Production of cGMP leads to relaxation of smooth muscle

Describe the Arachidonic Acid Cascade

1) G-protein activates Phospholipase A2 (PLA2) 2) PLA2 degrades phospholipids into arachidonic Acid (an eicosanoid) 3) Arachidonic acid metabolites and diffuse out of the cell and act as a ligand for GPCR cell membranes and adjacent cells

What does the hormone epinephrine (Adrenaline) cause some blood vessels to constrict and others to dilate

Receptor isoforms

When Epinephrine binds a-receptors it causes blood vessels to ____ where as if it binds to b2-Receptor it causes blood vessels to ________?

Constrict; dilate

True or False; A receptor can not be promiscuous

False

Phosphorylation can cause receptors to have a _____ affinity for ligands

lower

Receptor numbers can be upregulated or downregulated by what 3 things

Development Homeostatic challenges Disease states

The mechanism of opioid tolerance is the result of ____ being desensitized due to continuous exposure to an _____

Receptors; Agonist

Are G-proteins anchored by cytoskeleton? Why or why mot

No because cytoskeletons only exists in the cytoplasm

What does cAMP activate

PKA

What Kinase is linked with cAMP pathway, PKA or PKC

Adenylyl cyclase

Define Afferent in regards to Control pathways

back to the source

What are the two kinds of feedback loops?

Negative and Positive

Define the 3 key things that negative feedback does

1) Keeps system near a set point 2) Response acts to negate the stimulus 3) Response can Restore homeostasis, but cannot prevent the initial perturbation

Define the 3 key things that positive feedback does

1) Brings a system further from a set point 2) Response acts to reinforce the stimulus 3) Requires an outside factor to shut off

Give an example of both positive and negative feedback

Negative feedback = cruise control | Positive feedback = giving birth

Why is arachidonic acid involved in both intracellular and intercellular pathways.

It can diffuse out of the cell and have a paracrine affect on neighboring cells but can also produce an autocrine response due to being a secondary messenger

What is feedforward control?

When a small stimulus sets off a chain of events aimed at preventing a perturbation

Is positive feedback non homeostatic

no, it is

Lecture 5 & 6: Communication Flashcards

(69 cards)