Signal Transduction

7/21/2019 Signal Transduction

http://slidepdf.com/reader/full/signal-transduction-56da351b88fb6 1/17

Signal Transduction

M. M. Hamdi

13-09-20139.00am-10.00am



Outline of This presentation

This lecture gives an idea about:

• What is signal transduction alsoknown as cell signaling

• Basic mechanisms used for cell

signaling

• How do cells transmit signals

• Steps in the process of

extracellular signaling.

• Tools for cell signaling

• Basic Components cell signaling

• elevance of signal transduction

in medical science.

!t the end of this lecture "ou should be

able to:

#$ %xplain hormones and receptors and

its role in extracellular signaling.

&$ 'ist the steps in the process of


($ )iscuss the classification of


*$ )iscuss the overview of extracellular

signals.

Note: Extra reading & thinking helps in

exam and gives you idea on the power of

signal transduction in medical sciences



Introduction

• Human is a multicellular being.

• There are about #+, +++ +++, +++ +++cells -#+trilion cells$ in the bod"for example hepatoc"tes, m"oc"tes, leukoc"tes, BC, WBC and so

on making up &#+*## t"pes of cells in the bod".

10 X of these stacks !



Introduction

• 'iving cells are d"namicperforming various functions

including biochemical

reaction, growth, division, cell

death.

• Therefore those functions are

coordinated at cellular level.



Signal transduction or cell signalingThe basis for this coordination are:

#$ %xtracellular or intercellular cell

signaling, or communication

between cells. This communicationallows single cell to influence

behavior of other cells in a specific

manner.

&$ /ntracellular signal transduction

an intracellular events which affects

intracellular biochemical reactions.



a$ Communication via intercellular messenger .

eg0 /n low level of th"roid hormone

!nterior pituitar" secretes TSH.Through blood flow it was sensed

b" TSH on th"roc"tes

which then secretes Th"roxin.

!nother example0

/n water deprivation-plasma osmolalit" increase$

1osterior pituitar" secretes !)H

Through blood flow it was sensed

b" !)H on kidne" cells which then

decreases water excretion.

transduction



b$ Communication via 2ap 3unction.

eg. ! connection between one cell and another,

eg. 2ap 3unction between smooth muscle cell in 2/Tallows ions movement for electrical activit",

allows movements of metabolites

from one cell to another cells.

!nother example

Cardiac muscle use the similar mechanismto maintain unison contraction.

continuation

c$ Communication via surface protein.

eg. )irect communication between cells

/ntegrin receptor for cell migration

!nother example0

Cell adhesion uses integrin receptor



egarding the basic mechanisms used for intercellular signal transduction in

the diagram above

a$ /ntercellular messenger -T45$b$ 2ap 6unction -T45$

c$ Surface protein -T45$

/n diagram a$ above

State one intercellular messenger 777777777

State the site which the intercellular messenger binds 7777777777 State one effect of the intercellular signal transduction in a$ above 777777777.

Tutorial



"o# do cell transmit signal$• Consider endocrine s"stem where

sensor and effector are apartblood

circulation. But there are situationswhen cells stimulates itself

autocrine. Cells can also stimulate

neighbouring cellsparacrine eg.

during infection

• Consider rapid reflex eg. touching

of hot surface rapid electrical

signal 83ump9 on the m"elin sheath

• Consider information that travels

through neurons visione"esto

brainto effector organs"naptic

signaling



%reparem&'(

)'(

%rotein



These are common steps for cellular signaling:

• Signal -known as first messenger $ ie. s"nthesised4released then transported to target cell.

• -#$;pon receiving a signal -such as growth factor which for growth$, a membrane bound receptor becomes activated.

• -&$This in turn results in changes in cellular metabolism which transmit the signal further downstream. !s to transmit

the signal further downstream the activated receptor passes the signal onto components signal usu. Signaling

proteins which can be activated or deactivated.

• -($This in turn results in changes in cellular metabolism which elicit response re<uired b" the cell such as

proliferation, survival, h"pertroph" and so on.

• 5inall" signal attenuated which then terminates the response

Steps of cellular signaling



Steps of cellular signaling



Tools for *ell Signaling

b$1rotein kinaseattaches phosphate

to signaling proteins

-phosphor"lation$ = activates

c$1rotein phosphatase

removes phosphate from signaling

proteins

-dephosphor"lation$ = deactivates

This is how signalingmolecules are reversibl"

being

activated4deactivated.

Signaling proteins are tools for cell signaling for example:

$eceptor

for detection of incoming signal

21C largest famil" of membrane bound receptor have no c"toplasmic t"rosine kinase domain -use 2protein for activation$

T>s such as %25 re<uires activation have

phosphor"latable region -also known as t"rosine kinase

region$

note that not all receptor are membrane bound eg. !ndrogen receptor

d$egulator" 2T1ase

function as switches and exist in active form to transmit signal0 in inactive formrepress signal further downstream

e$!daptor proteins

mediates signal transmission between signaling proteins



medical sciences

#?.*@ of total

genes

involved in

signal

transduction



• Th"roid hormone• Steroid hormone such as

glucorticoid

• Ax"tocinuterine contraction• Blood glucose b" insulin

aintaining population of health" cells

through apoptosis

%tc.

medical sciences

%xample of a feedback mechanism

H"pothalamopituitar"th"roid axis

/ntercellular signaling involve in homeostasis such as0

aintaining hormone level

through feedback mechanism



/ntracellular signaling protein form modules which makes up

signaling pathwa"s

Signaling pathwa"s:

• egulates various ph"siological functions such as0• /ntracellular Calcium release for muscle

contraction.• 1aracrine signaling b" itric Axide in smooth

muscle• Cell motilit"• Creating new blood vessel eg. otch receptor • Contact inhibition• %tc.

• odulates numbers of ph"siological function such as

phosphor"lation of "osin light chain in smooth

muscle contraction.

• Too man" signaling pathwa"s which its ph"siological

functions are not known.

• 1otential on going researches to characteriDe

signaling pathwa"s to a particular ph"siological

function. !s to understand, manipulate and create

new drug4treatment.

medical sciences



&eferences

• ,rauss .2003/. iochemistr ofsignal transduction and regulation 3rd edition

• olecular *ell iolog 2000/. odishet. al. 4th edition.

• (n cell iolog5 molecular iolog or

iochemistr te6took.

Signal Transduction

Documents