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