chapter 11 cell communication dr. joseph silver. this chapter deals with - how cells receive...
TRANSCRIPT
Chapter 11
Cell Communication
Dr. Joseph Silver
this chapter deals with- how cells receive messages
- what changes take place in the cell - and what changes take place in the
nucleus
The goal is to understand3 processes
1. reception (you pick up a message)2. transduction (cell response to message)
3. response (what work the message tells the cell to do)
how one cell signals another cell is defined by the distance from the
signal source to the receptor
5 types are described
-direct contact (fig. 11.4)-paracrine (fig. 11.5a)-endocrine (fig. 11.5c)-synaptic (fig. 11.5b)
-autocrine (stimulates same cell)
the key to everything thatgoes on in a cell is phosphorylation
ordephosphorylation
see fig. 11.8 , 11.10, and 11.12
start or stopinhibit or activateturn on or turn off
all happens byadding or removing
a phosphate functional group(see page 219)
receptors are definedby their location- on a membrane- in a membrane
- trans membrane (through)- cytoplasmic
there are three types ofmembrane receptors- channel receptors-enzyme receptors
-G protein-coupled receptors
some receptors such as steroid hormone receptors
are not in the membranebecause the message can pass right through
the membraneso
activation (transduction) takes place in the cytoplasm
there are three very importantkinases in cells
RTK, RSK, RTyK(receptor threonine kinase – serine kinase –
tyrosine kinase)these kinases add or remove phosphate
from molecules and influence most reactions taking place
in every cell
see fig 11.15 to see- message to receptor linkage
- autophosphorylation- activation of protein by phosphorylation
then
Go to fig 11.16 to see- activation of 2nd and 3rd messengers
- activation of enzyme- result of work stimulated by enzyme
activity
look at fig 11.16 to seeamplification of events
another word for multiplication
in some cases instead of a 1 to 1 relationship
there isa 1 to 2, then 2 to 4, then greater
amplification as more and more reactions or systems
are amplified or inhibited
We have previously studiedhomeodomain proteins (found in all
organisms)membrane lipid domains (found in all cell
membranes)and
multienzyme complexes (increases efficiency)now they are giving in fig 11.18
another name for a multienzyme complexscaffold proteins
which holds in placea number of kinase close to each other
for increased efficiency
Now look at fig 11.9 & 11.10 to see the process
from ligand binding to receptorto
response by cell
there are many kinds of 2nd and 3rd etc. messengers
Cyclic AMPinositol phosphates
calciumand more
apoptosis
programmed cell death
damaged, infected, wrong code,
signal for apoptosiscan come from inside or outside the cell
Ced genes (cell death genes) present as inactivebut when activated
produce a cascade of proteasesknown as
caspases and nucleaseswhich force cell death