Cell to cell communication Flashcards
Categories of chemical signaling (4)
Free diffusion: adjacent or distant
Cell signal to itself
Cell to cell contact
The adjacent cell communication is in
With the interstitial space
Extracellular signaling can (5)
- Coordinate the aggregation of movement of cells
- Initiate control under certain environmental conditions
- alter gene expression
- control metabolic processes between cells
- Contribute to nerve conduction
What metabolic processes can the extracellular signaling control (2)
Synthesis and secretion of proteins
Composition of intracellular and extracellular fluid
Types of signal molecules (4)
Small lipophilic molecules
Small hydrophobic molecules from a.a.
Gases
Physical stimuli (light)
What is a ligand
A signaling molecule
What does reception mean
Molecule to molecule contact
The target cell action depends on (4)
Signals that are present
Receptors that the target cell expresses on surface or IC
Signaling cascades
IC targets
What does ligand do
Bind together
What is a ligand
Molecule that binds to specific molecule called receptor
What is needed in order to detect a signal
The receiving cell must have the right receptor for that signal
What happens when a signaling molecule binds to a receptor
Alters the shape and activity of the receptor causing a change in the cell
T or F
A specific ligand with have a specific receptor that can bind to other ligands
False
Receptors are specific for one ligand
Types of ligands (2)
Those that enter the cell
Those that bind to receptors outside of cell
Properties of ligands(3)
Hydrophobic
Lipophilic
Can pass through membrane and bind to IC receptros in the nucleus or cytoplams
What type of ligand can directly travel across the membrane due to its small size
Nitric oxide (NO)
What is the key role of nitric acid as a ligand
Activate a signaling pathway in the smooth muscle surrounding blood vessels
Can make a muscle relax and blood vessels expand (dilate)
Properties of water soluble ligands (3)
Polar or charged
Cannot pass or cross the PM
Bind to extracellular domains of cell surface receptors staying on the outer surface
Example of water soluble ligand
Peptide protein ligands such as insulin and certain neurotransmitters
Different types of neurotransmitters (4)
Some are peptides
Other small hydrophilic organic molecules
Standard a.a.
Modified or non standard
What peptides are neurotransmitters(2)
Oxytocin
Endorphin
What types of hydrophilic molecules are neurotransmitters
Monoamines such as dopamine
What standard a.a. are neurotransmitters (2)
Glutamate and glycine
Examples of ligand (6)
Steroid hormones Growth factors and hormones Neurotransmitters Nitric oxide Light or photo transduction Pressure or mechanotransducyion
Types of receptors (2)
Internal
Cell surface receptors
Internal receptors are where
IC and in the cytoplasm of the cell
Internal receptors respond to what type of ligand
Hydrophobic ligand that can travel across the PM
Ligand-binding causes
A conformational change that exposes the DNA binding site on protein
What causes the initiation of transcription and gene expression in a cell
When the ligand receptor complex moves into the nucleus and binds into a specific regulatory region of chromosomal DNA
T or F
With the internal receptors after the ligand has binded to the receptor and moved in the nucleus, you need other types of receptors and signals.
False
No need
What are the cell surface receptors
Membrane anchored (integral) proteins that bind external ligand molecules
What are the cell surface receptors also called
Transmembrane receptors
What do the cell surface receptor do to the PM
Spans it and produce a signal transduction in which EC signal is converted into IC signal
Main components of the cell surface receptors (3)
External ligand binding domain
Hydrophobic membrane spanning region
IC domain inside cell
Autocrine signals are produced by
What does that mean
Signaling cells that can also bind to the ligand that is released
Meaning that signaling cells and target cells can be the same or similar
Autocrine signaling can (2)
Regulate inflammation and pain responses
Signal apoptosis when the cell is infected by a virus
T or F
Abnormal autocrine signaling contributes to uncontrolled growth of cells such as cancer cells
True
Endocrine signaling are
Signals from distant cells originated from endocrine cells
T or F
Endocrine signals can produce faster responses but have a short lasting effect
False
Slower response
Long lasting effect
Ligands released from the endocrine signals are called
Hormones
What are hormones
Signaling molecules that are produced in one part of the cell but affect other body regions
How can hormones travel to target cells
Through the blood stream
What happens to the hormones when they act on target cells
They get diluted and are present in low concentrations
Paracrine signaling examples
Synaptic signaling
What is synaptic signaling (2)
Nerve cells transmit signal
Process named for the synapse, the junction between two nerve cells where signal transmission occurs
Types of cell to cell connections (4)
Tight junctions
Adherence junctions
Desmosomes
Gap junctions
Tight junctions
Seal the adjacent epithelial cells in a narrow band
Where can i find a tight junction
In lung epithelium
Adherence junctions
Provide strong mechanical attachments between adjacent cells
Where can i see adherence junctions
Cardiac muscle
Desmosomes
Hold a cell tightly together by linking IC to the intermediate filament cytoskeleton
Gap junctions
Allow signaling between cells
How do animal cells connect between PM and neighboring cells
Gap junctions
In plants what is the connection between plasma M and other cells
Plasmodesmata
Stages of signaling (3)
Ligand binding
Transduction
Cellular response
What happens in transduction
Amplification and spreading across specific pathway
What happens in cellular response (4)
Gene transcription
Cell proliferation
Differentiation
Cell survival
T or F
Ligands cannot act in 2 or 3 of the cell to cell signaling
False they can
Example of a ligand acting in more than one cell signaling
Epinephrine
Acts as a neurotransmitter and systemic hormone
So paracrine and endocrine signaling
What protein hormone is synthesized as the exoplasmic part of plasma membrane protein that can bind and signal an adjacent cell by direct contact
Epidermal growth factor
T or F
Ligands exhibit versatility just like receptors
FALSE
Ligands show versatility for receptors but the receptor displays high specificity to that ligand
Meaning a ligand can bind to many receptors while the receptor can only bind to a specific ligand
T or F
The response to a chemical signal decreases when EC concentrations of signals increase
False
Increase when EC concentrations increase
The more EC ligands means
The more responses
Maximum cellular response happens when
Saturation is reached due to finite numbers of receptors
T or F
Chemical signals don’t need to compete for a receptor
False
If they have similar structures they will and can compete for the same receptor
Can the same receptor trigger a different response in a ligand
Yes
An example of a receptor that can have different effects on a ligand
Explain
Acetylcholine
Release from a neuron adjacent to a striated muscle will trigger contraction where as if it was adjacent to the heart muscle it will slow down the rate of concentration
Where is acetylcholine found
On surface of striated muscle cells, hear muscles, and pancreatic acinar cells
Effects of acetylcholine in pancreatic acinar cells
Triggers exocytosis of secretory granules that contain digestive enzymes
T or F
Different ligand-receptor complexes can induce the same cellular response in some cell types
True
Example of specific mediated responses from different hormone-ligand complexes
Activation of epinephrine and glucagon receptors in liver cells by binding to their respective ligands induces synthesis of cAMP (2nd messenger)
So effect is identical in liver
T or F
Ligands can be metabolized for other products, is an intermediate in cellular activity and has important enzymatic activity
False
I doesn’t do anything
What is the function of the ligand
Bind to the receptor
Classes of cell surface receptors (4)
G protein coupled receptors
Ion channel receptors
Tyrosine-kinase linked receptors
Receptors with intrinsic enzymatic activity
Examples of G protein CR (3)
Epinephrine
glucagon
Serotonin
Examples of ion channel receptors
Acetylcholine
Example of Tyrosine-kinase linked receptor (2)
Erythropoietin
Interferon
The name of classes of receptors refer to
The mechanism by which the receptors transform EC signals into IC ones
T or F
Cell surface receptors can make changes in the function of the cell without actually going inside the cell
Explain
True
Because they work/ interact with EC and IC signals
Ion channels receptors are also called
Ligand gated ion channel receptors
The conformational changed caused by ligand binding in the receptor (ion channel receptor)allows what type of ions to pass through (5)
Ca K Na Mg H
What ligands work mostly with ion channel receptors (2)
Neurotransmitter such as glutamate
Acetylcholine
Example of receptors with intrinsic enzymatic activity
Explain
Atrial naturetic protein
Binds to its receptor causing a reduction in blood volume
So a decreased in cardiac output and systemic blood pressure occurs
Lipolisis increases and renal sodium decrease
The overall effect is to counter increase in blood pressure and volume caused by the renin angiotensin system
Enzyme linked receptors lack
Lack intrinsic catalytic activity but ligand binding stimulates formation of a dimeric receptor
What happens to the dimeric receptor formed by the ligand bonding in enzyme linked receptors
Interacts and activates cytosolic protein-tyrosine kinases
When the ligand binds, it activates a signal transduction cascade, what is the first thing released from this
G protein coupled receptors
The activation of an enzyme by a G protein generates what
A specific 2nd messenger or modulates ion channel, changing the membrane potential
Which type of receptor is the largest family of cell surface receptors
G protein coupled receptors
Speed of effect diverging effects (4)
Opening another channel via internal binding site Increase or decrease transcription Protein modification (phosphorylation included) Other downstream effects
GPCR regulate (4)
Hormone secretion in the pancreas/gluconeogenesis: glucagon
Platelet mediated blood clotting: thrombin
Blood pressure regulation: angiotensin II, epinephrine
Mood: serotonin
Examples of GPCR (4)
EPINEPHRINE
ANGIOTENSIN II
SEROTONIN
GLUCAGON
Structure of GPCR (4)
Seven hydrophobic transmembrane segments
EC amino terminus
IC carboxyl terminus TM receptor
Coupled inactive G protein bound to trimetic subunit (alpha, beta, gamma)
There are importance differences between receptor categories in part due to
Speed of effect
Duration of effect
When we talk about speed of effect, what happens when the ligand binds to an ion channel receptor
It opens the channel, so there is an immediate flow of ions inducing excitatory postsynaptic or inhibitory postsynaptic potentials
When we talk about speed of effect, what happens when the ligand binds to the protein/enzyme linked receptor
Then a cascade of secondary messengers system occurs
When we refer to the duration of the effect, what happens when the ligand binds to the ion channel receptor
They’re usually very quick in response
When we refer to the duration of effect, what happens when the ligand binds to the protein enzyme linked receptor
Depending on the receptors they’re usually delayed
Rapid responses in the organisms are mediated by (2)
Peptide hormones
Catecholamines such as epinephrine, norepinephrine, dopamine
How long does the peptide hormone persist in blood before being degraded by blood and tissue proteases
Sec or mins
Catecholamines are rapidly inactivated by
Different enzymes or taken by specific cells
Signaling molecules and their receptors (5)
Steroid hormones and the steroid receptor superfamily
Nitric oxide and carbon monoxide
Neurotransmitters
Peptides hormones, neuropeptides and growth factors
Eicosanoids
Examples of steroid receptors (4)
Steroid hormones
Vitamin D
Retinoic acid
Thyroid hormone
Steroid hormones are
Small hydrophobic molecules that diffuse across the PM of target cells
Bins to IC receptors
Steroid hormones function as
Transcription factors to direclty regulate gene expression in response of ligand binding
Neurotransmitters are (2)
Small hydrophilic molecules
Carry signals between neurons or between neurons and target cells
Neurotransmitters bind to
Ligand gated Ion channels
Which one is the widest variety of signaling molecules in animals (3)
Peptide hormones
Neuropeptides
Growth factors
Eicosanoids are
Class of lipids that function in paracrine and autocrine signaling
Examples of receptors bind to enzymatic activity include (3)
Protein-tyrosine phosphatases
Protein-serine/threonine kinases
Guanylyl cyclases
Tyrosine kinase ligand receptors are
Receptor for most growth factor
Signal transduction cascades (3)
IC signaling pathways
Amplify message
Produce multiple IC signals for every one receptor that is bound
Example of signaling cascade form an enzyme linked receptor
MAPK pathway
T or F
MAPK communicate by adding phosphate groups to a neighboring cell protein which acts an on or off switch
True
Which receptor is a transmembrane molecule that can open or close a channel that allows cations to travel in and out the cell
Inotropic receptors
When to ionotropic receptors open up
When the ligand binds to the receptor
Domains of ionotropic receptors (4)
Extracellular amino terminal domain (ATD)
EC ligand binding domain (LBD)
Four transmembrane domains (CTD)
IC carboxyl terminal domain
Example of ionotropic receptor
Ionotropic glutamate receptor
Ionotropic glutamate receptos allow the passage of
Na
K
Ca sometimes
In response to glutamate binding
T or F
Ionotropic glutamate receptor regulate the majority of excitatory neurotransmission within the cell
True
T or F
All ionotropic receptors produce excitatory postsynaptic current at the same speed and duration
False
At different speed and duration
IGRs (ionotropic glutamate receptors) are found where
On the pre and postsynaptic cell membranes primarily between the CNS
IGRs are divided into subfamilies according to affinities (3)
AMPA
NMDA
Kainate
NMDA have an internal site for
Mg
NMDA receptors are permeable to what molecule
Ca
T or F
Metabotropic receptos have channels
False
Metabotropic link to a small chemical called
G protein
What happens when the metabotropic receptor activates the g protein
G protein activates 2nd messengers
What is the function of the 2nd messenger
Go and activate other particles
Example of metabotropic receptos
Glutamate
T or F
Ionotropic ligands are degraded slower than metabotropic
False
Its faster so channel closes fast
What type of second messenger is Involved in visual reception in vertebral eye
cGMP
Which are the 2nd messengers(6)
cAMP cGMP Phospholipids Ca IP3 DAG
Metabolic functions controlled by hormone induced second messengers include (3)
Uptake and utilization of glucose
Storage and mobilization of fat
Secretion of cellular products
T or F
Removal or degradation of a ligand or second messenger or inactivation pf the ligand or receptor does not cause any effect in the cellular response since these actions are a part of the signaling transduction
False
It terminates the cellular response to an EC signal
The epinephrine receptor is coupled to _______ _____ via a ______ _________ that stimulates enzymatic activity.
What does this do to cAMP
Adenylyl cyclase
G protein
Increase the concentration of cAMP IC
How does cAMP signals the breakdown of glycogen
So cAMPs effects are mediated by PKA which is a tetramer with 2 catalytic parts and 2 regulators.
cAMP will bind to the regulator site of PKA breaking the catalytic parts off.
This catalytic parts are active. And from this phosphorylates kinase are activated.
Phosphorylase kinase phosphorylates and activates glycogen phosphorylase which is then broken down into glycogen and glucose-1-phosphate
What is GEF
Guanine nucleotide exchange receptor
What does GEF do
Exchange GDT to GTP bound to the alpha subunit in the G protein
The exchange of GDT to GTP triggers what in the G protein
The dissociation of alpha subunit from the beta-gamma subunits and the receptor as a whole
G alpha s does what
Stimulation of cAMP
Is a cAMP dependant pathway
Which one is the cAMP dependent pathway
Gas
What is the cAMP dependent pathway used for
As transduction pathway for some hormones
What hormones use the cAMP dependent pathway (8)
ACTH TSH LH PTH Calcitonin Glucagon hCH Epinephrine
ACTH
Stimulates synthesis and release of cortisol
TSH
Stimulates and release of T4 (thyroid glands)
LH
Stimulates follicular development in women
Spermatogenesis in men
PTH
Increases Ca levels in blood
Calcitonin
Decrease Ca levels in blood
Glucagon
Stimulates glycogen breakdown in the liver
hCG
Promotes cellular differentiation, apoptosis
Epinephrine
Released by adrenalmedula during fasting state
Stimulates glycogenesis and actions of glucagon
G alpha i does what
Inhibit cAMP
What molecule uses Gai
Insulin
G alpha q/11
Stimulates phospholipase c which cleaves PIP2 into IP3 and DAG
What is the inositol dependent pathway
G aq/11
The inositol dependent pathway serves for what hormones (5)
ADH TRH TSH Angiotensin II GnRH
ADH
Vassopresin, induces synthesis and release of glucocorticoids
ADH induces
Vasoconstriction
TRH
Induces synthesis and release of TSH
Angiotensin II
Aldoterstosterone synthesis and release
GnRH
Synthesis and release of FSH and LH
G alpha 12/13
Involved with the Rho family
Involved with the remodeling of cells and regulation of cell migration
G alpha t is known as
Transducon
Transducin is found where
In rod and cone photoreceptors of eye
Transducin activates what
Which does what
Phosphodiesterase to break down cGMP
In protein kinases what is the common sites of phosphorylation (3)
Serine
Threonine
Tyrosine
Where are places where the protein kinases can be found besides in the receptor
In the cytosol or associated with PM
What type of kinases do animals have (2)
Those directed toward tyrosine
Those directed to serine or threonine
In protein synthesis PKA activates what
CREB which binds to cAMP response element
What happens to the protein when CREB binds to the cAMP response elements
It alters the transcription and the synthesis of the protein
Activated PKC are translocated to the PM by
RACK proteins
T or F
PKC HAVE A SHORT TERM ACTIVATION
FALSE
IS LONG TERM ACTIVATION
RTK is
Receptor tyrosine kinase
What happens if a growth hormone binds to the EC domain of a RTK
Triggers dimerization
Dimerization of RTK leads to (2)
Rapid activation of the proteins cytoplasmic kinase domains
The activated receptors then becomes autophorphorylated into specific IC tyrosine residues
T or F
Each molecules of epinephrine activates only a single receptor which can activate many G proteins
True
In animal cells, increase of cAMP activates transcription of specific target cells that contain a regulatory sequence called
CRE
cAMP RESPONSE ELEMEMNT
PKA can phosphorylate the transcription factor called
CREB
What mediates cAMP actions
PKA
How does cAMP stops signaling
Degradation by phosphodiesterase
T or F
Many of the odorant receptors in sensory neurons in the nose are G proteins CR that stimulate adenylyl cyclase leading to an increase in EC cAMP
False is in IC
What messenger relaxes smooth muscles
cGMP
Relaxation of vascular smooth muscles lead to
Vasodilation and increase of blood flow
IP3 causes the release of
Ca
Hydrolysis of PIP2 yields
DAG
IP3
In electrically excitable cells of nerve and muscles, levels of cytosolic Ca are increased by opening of (2)
Voltage gated ca channels in pm
Ryanodine receptors in ER and SR
Phorbol ester promote
Growth of tumos in animals
Acetylcholine is degraded by
Cholinesterase in miliseconds
What are decoy receptors
Cell surface receptors that bind the ligand but do not convey the signal onward in the pathway
What happens if the ligand cannot be degraded or sequestrated
Then the target cell may be desensitized
How does desensitization occur(3)
Inactivation of receptor (blocking its interaction with downstream signaling components)
Sequestering the receptor into endocytic vesicles
Degrading the receptors in lysosomes
Activated GPCRs can be desensitized when
When they are phosphorylated by different protein kinases
The phosphorylated GPCRs then bind to
Arrestin
Can arrestin mediate endocytosis receptors?
Yes
Homeostasis of Ca levels in the cytoplasm is maintained by (3)
Calcium-permeable channels
Transporters
ATPases
Ca is required by a lot of proteins which in turn regulate (3)
Asexual and sexual development
Circadian clock
Protein folding
What is the most common signaling pathway that increases cytoplasmic calcium concentration
Phospholipase C pathway
PLC is activated by
Cell receptors including G proteins and tyrosine kinase receptors
How is PLC activated (4)
PLC hydrolyzes PIP2 to form IP3 and DAG
DAG recruits PKC attaching it to the plasma membrane
IP3 diffuses to the ER and binds to an IP3 receptor which serves as a Ca channel and releases Ca
Ca binds to PKC activating it
Depletion of calcium from the ER will lead to Ca entry from outside the cell. This occurs by activation of
Store operated channels
SOCs
CRAC refers to
The inflowing Ca current that results after stored calcium reserves have been released
CRAC means
Calcium restored activated Ca current
CRAC protein 1 is a calcium selective ion channel that is encoded by
Orai 1
In excitable cells, Ca is essential for regulating processes such as (5)
Exocytosis Gene regulation Cell growth and proliferation Enzyme control Apoptosis
Ca as a second messenger functions for (6)
Muscle contraction Cellular motility Fertilization Cell growth or proliferation Neurogenesis Learning and memory
High levels of Ca in the cytoplasm can cause
Apoptosis in the cell
Example of a Ca binding protein
Calmodulin
Calmodulin is activated by
Ca when the concentration of cytosolic Ca increases
Example of Ca/Calmodulin dependent protein
Myosin light chain kinase
A transcription factor phosphorylated by CaM is
CREB
T or F
LDL receptors are recycled through endocytosis
True
Receptor mediated endocytosis in cell signaling
Implicated in transducing signals from the cell periphery to the nucleus
Arresting binding to the receptos is involved in
Receptor desensitization
Where are IC receptors found
In the cytoplasm of cell
Ic receptors respond to
Hydrophobic ligands that are able to travel across the PM
The IC ligand receptor complex move into the
Nucleus and binds to the chromosomal DNA
T or F
For the IC ligand receptors you need several receptor signals for the transcription of the gene in nucleus
False
No more is needed
IC receptors are also known as
Nuclear hormone receptors
Which are the nuclear hormone receptors (4)
Steroid hormone
Thyroid hormone
Retinoid
Vitamin D
