Social cells Flashcards
cell to cell communication
how do cells interact with each other?
by releasing extracellular molecules influencing the behaviour of their neighbour or more distant cells
signalling molecule?
the ligand
what does cell growth, differentiation metabolism and death depend on?
on cell to cell communication
ligands?
the signalling molecules released by the cell to communicate
receptors?
the receiving molecules capable of translating the extracellular signal into an intracellular modification
examples of short distance communication?
contact-dependent (juxtacrine)
autocrine signalling
paracrine signalling
examples of long distance communication?
synaptic and endocrine signalling
juxta?
near
auto?
self
para?
beside
endo?
within (the body)
contact-dependent communication example?
immune response
autocrine signalling example?
proteins, RNAa etc
paracrine signalling example?
proteins RNAs etc,
examples of synaptic communication?
neurotransmitters
examples of endocrine signalling communication:
hormones
krine?
secrete (or separate)
describe endocrine signalling:
hormones - slow diffusion in the bloodstream - days to have an effect
describe synaptic signalling:
neurotransmitters, 100m/sec for the electrical impulse
millisec for the release/uptake of neurotransmitters
describe paracrine signalling:
local mediator, proteins RNAs sugars, gases, lipids
local mediator controls speed of message delivery
What distance is endocrine signalling?
long distance
what are some diseases associated with hormonal deficiency?
diabetes
osteoporosis
reproduction and infertility
growth retardation
ligands in paracrine signalling
produced in low levels and quite tightly controlled
antagonist and inhibitors?
two ways to interfere with signalling
antagonist
blocking receptors
inhibition
stopping signal from getting out
what is the distance with paracrine signalling?
short distance cell-to-cell communication - the exact distance is not quantified
What are disease associated with defects in paracrine signalling?
inflammation and allergies
structure of histamine?
amino acid derivative
source of histamines?
mast cells
actions of histamines?
vasodilation
contracts airways
local mediators messengers?
histamines, thromboxane, leukotrienes
structure of thromboxane?
lipid derivative
structure of leukotrienes?
lipid derivatives
source of thromboxane?
blood platelets
source of leukotrienes?
inflammatory cells
actions of thromboxane?
vasconstriction
causes platelet aggregation
actions of leukotrienes?
constrict airways
attract inflammatory cells
make blood vessels leaky
what are the 3 forms of juxtacrine/contact dependent signalling?
membrane proteins on each cell interact
membrane proteins interact with part of an extracellular matrix
junctions link cells allowing small molecules to pass between
describe how membrane proteins on each cell interact:
antigen presenting cells trigeering differentiation of types of T cell into Th or Tc
describe how membrane proteins interact with part of an extracellular matrix:
integrins and RTKs allowing interaction with ECM to regulate processes such as cell division
describe how junctions link cells allowing small molecules to pass between?
gap junctions allowing contraction of cardiac cells or propagating electrical synapses
slide 15
what is synaptic signalling?
it is technically short distance but allows rapid long distance signalling
what do the vast majority of signalling molecules bind to?
receptors
what does the ligand-receptor interaction promote?
promotes a conformational change in the receptor
where are most of the receptors situated?
on the plasma membrane but some can be intracellular
what can some messengers do?
they can also bind ion channels or cause the synthesis of a second messenger
what does the cell need to do in order to pass on the message?
the cell needs to express the right receptors for the messenger to pass on the message (competent cell)
different cells contain different…?
different pools of receptors or different concentration of receptors
19,20
what are ligands?
hormones
meaning of lipophilic?
tending to combine with or dissolve in lipids or fats
what tends to be lipophilic?
the hormones in the endocrine signalling
explain how endocrine signalling is very specific?
only cells/organs presenting appropriate receptors will be influenced
what can start a paracrine signalling?
a vast range of different ligands: growth factors, gases and inflammatory mediators
describe the concentration of the ligands in paracrine signalling:
it is usually low and can be controlled in several ways
how can the concentration of ligands be controlled in paracrine signalling?
enzymes
ECM
antagonists
inhibitors
what is autocrine signalling?
the cell signalling to itself
what ligands promote autocrine signalling?
cytokines
growth factors
hormones
what can autocrine signalling do?
it can decrease or promote the signalling initiated by the cell itself (negative or positive feedback effect)
how is autocrine signalling used - in context?
it is one way cancer cells can promote their own survival and division
what is juxtacrine signalling also known as?
contact dependent signalling
what is juxtacrine signalling?
signalling directly between two cells via direct contact
describe what the distance is of synaptic signalling?
it is technically short distance but it does allow rapid long distance signalling
what does synaptic signalling do?
coordinate the behaviour of cells far apart from each other
what does synaptic signalling do to electrical impulses?
they are transformed into chemical signals
what does synaptic signalling occur between?
it is very specific, between neurons, between sensor and neuron or between neuron and effector cell
what do the vast majority of signalling molecules bind to?
receptors
what can some messengers bind to?
ion channels or they can cause synthesis of a second messenger
what is a competent cell?
a cell that needs to express the right receptor for the messenger to pass on the message
one messenger can activate…
different isoforms of the same receptor, inducing different biological effects
one receptor can bind…
different ligands and with different affinity, again mediating different biological effects
signal amplification?
there can be an amplification of the signal within the cell and cross-talk between different signalling cascades
what are the four main types of receptors?
ion channel coupled receptors
G-protein coupled receptors
Enzyme coupled receptors
Nuclear receptors
what type of receptor is ion-channel coupled receptors?
ionotropic receptors
what is different about the four main receptors?
they have different molecular structures ans they work at different speeds and/or for different lengths of times
nuclear receptors are…
intracellular
what do G-proteins coupled receptors carry out?
metabotropic transmission
what is the main type of enzyme coupled receptors?
tyrosine kinase
gap junctions?
like plasmodesmata in plant cells
they are connections between two close cells that allow ion/other small molecules to pass - so they don’t have to pass across the cell membrane
what signalling is local?
paracrine signalling
and synaptic signalling
