celltocellcommunication-101021235148-phpapp01

7/30/2019 celltocellcommunication-101021235148-phpapp01

1/29

Cell to Cell Communication


2/29

2

Cell to Cell Communication

Communication between cells requires:

ligand: the signaling molecule

receptor protein: the molecule to which the

receptor binds-may be on the plasma membrane or

within the cell


3/29

3


4/29

4

Cell Communication

There are five basic mechanisms for cellular

communication:

1. Direct contact

2. Paracrine and Autocrine signaling

3. Endocrine signaling

4. Synaptic signaling


5/29

5


6/29

6

Cell Communication

When a ligand binds to a receptor protein,

the cell has a response.

signal transduction: the events within the

cell that occur in response to a signal

Different cell types can respond differently to

the same signal.


7/29

7

Cell Communication

A cells response to a signal often involves

activating or inactivating proteins.

Phosphorylation is a common way to

change the activity of a protein.

protein kinase an enzyme that adds a

phosphate to a protein

phosphatase an enzyme that removes a

phosphate from a protein


8/29

Three Stages of Signal Transduction

1. Reception of extracellular signal by cell

2. Transduction of signal from outside of cell

to inside of celloften multi-stepped

Note not necessarily transduction of ligand

3. CellularResponse

Response is inititiated and/or occurs

entirely within receiving cell


9/29

Three Stages of Signal Transduction


10/29

T

hreeS

tages 2a. Transduction

2b. Transduction

2c. Transduction

2d. Transduction

1. Reception

3. Response

Responses usually involve increasing or decreasing some Proteins Function


11/29

T

hreeS

tages

2a. Transduction

2b. Transduction

1. Reception

3. Response


12/29

12

Receptor Types

Receptors can be defined by their location.

intracellular receptor located within thecell

cell surface receptorormembranereceptor located on the plasma

membrane to bind a ligand outside the cell


13/29

13

Receptor Types

There are 3 subclasses of membranereceptors:

1. channel linked receptors ion channel

that opens in response to a ligand2. enzymatic receptors receptor is an

enzyme that is activated by the ligand

3. G protein-coupled receptor a G-protein (bound to GTP) assists intransmitting the signal


14/29

14


15/29

15


16/29

16

Intracellular Receptors

steroid hormones

-have a nonpolar, lipid-soluble structure

-can cross the plasma membrane to asteroid receptor

-usually affect regulation of gene expression

An inhibitor blocks the receptor from binding

to DNA until the hormone is present.


17/29

17

Intracellular Receptors

A steroid receptor has 3 functional domains:

1. hormone-binding domain2. DNA binding domain

3. domain that interacts with coactivators to

affect gene expression


18/29

18


19/29

19

Receptor Kinases

Receptor tyrosine kinases

-membrane receptor

-when bound by a ligand, the receptor isactivated by dimerization and

autophosphorylation

-activated receptor adds a phosphate totyrosine on a response protein

-an example is the insulin receptor


20/29

20


21/29

21


22/29

22

Receptor Kinases

kinase cascade a series of protein

kinases that phosphorylate each other in

succession

-amplifies the signal because a few signal

molecules can elicit a large cell response

mitogen-activated protein (MAP) kinases

are activated by kinase cascades


23/29

23

G-Protein Coupled Receptors

G-protein protein bound to GTP

G-protein-coupled receptor (GPCRs)

receptors bound to G proteins

-G-protein is a switch turned on by the

receptor

-G-protein then activates an effector protein

(usually an enzyme)


24/29

24


25/29

25

G-Protein Coupled Receptors

Once activated, the effector proteinproduces a second messenger.

-second messenger generates the cellular

response to the original signalFor example one common effector protein

is adenylyl cyclase which produces

cAMP as a second messenger.Other second messengers: inositol

phosphates, calcium ions (Ca2+)


26/29

26


27/29

27

Cell-to-Cell Interactions

Cells can identify each other by cell surface

markers.

-glycolipids are commonly used as tissue-

specific markers

-major histocompatibility complex (MHC)

proteins are used by cells to distinguish

self from non-self


28/29

28

Cell-to-Cell Interactions

Cells within a tissue are connected to each

other by cell junctions

1. tight junctions create sheets of cells

2. anchoring junctions connect the

cytoskeletons of adjacent cells

3. communicating junctions permit small

molecules to pass between cells

- gap junctions


29/29

29

celltocellcommunication-101021235148-phpapp01

Documents

Transcript of celltocellcommunication-101021235148-phpapp01