BSC-2010 Lecture Notes - Lecture 9: G Protein–Coupled Receptor, Paracrine Signalling, Cell Membrane

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20 Oct 2016
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CH11
Cells can signal to each other an interpret the signals they receive from other
cells and the environment
Cells in a multicellular organism communicate via signaling molecules
In local signaling, animal cells may communicate by direct contact
In many other cases, animal cells communicate using secreted messenger
molecules that travel only short distances
This type of local signaling in animals is called paracrine signaling
Synaptic signaling occurs in the animal nervous system when a
neurotransmitter is released in response to an electric signal
In long distance signaling, plants and animals use chemicals called hormones
Earl W. Sutherland discovered how the hormone epinephrine acts on cells
Sutherland suggested that cells receiving signals went through three
processes
o Reception
o Transduction
o Response
Most water soluble signal molecules bind to specific on receptor proteins
that span the plasma membrane
Three main membrane receptors
o G protein coupled receptors - are the largest family of cell-surface
receptors
o Receptor tyrosine kinases - are membrane receptors that attach
phosphates to tyrosines
o Ion channel receptors - acts as a gate when the receptor changes
shape
Intracellular receptor proteins are found in the cytoplasm or nucleus of
target cells
Phosphorylation and dephosphorylation of proteins is a widespread cellular
mechanism for regulating protein activity
Protein phosphatases rapidly remove the phosphates from proteins, a
process called dephosphorylation
Second messengers are small, nonprotein, water-soluble molecules or ions
that spread throughout a cell by diffusion
Cyclic AMP (cAMP) is one of the most widely used second messengers
Adenylyl cyclase, an enzyme in the plasma membrane, converts ATP to
cAMP in response to an extracellular signal
Calcium ions (Ca2+) act as a second messenger in many pathways
Scaffolding proteins are large relay proteins to which other relay proteins
are attached
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