cell communication

1. Presented By-Arun Kumar Patel
M.Sc (Zoology) 4th semester
Allahabad University.
Communication between cells and
their environment

2. Introduction
 Cells interacts with extracellular material to form
special defined tissue.
 These interactions are crucial to the formation of
epithelial tissue and connective tissue ,which are
essential for various cellular activities.
 Cell need to be able to communicate with other
cell and respond to environmental change.
 Cell communication is important for various
cellular activities in multicellular organism.
 Unicellular organism also do cell communication
by secreting signal molecule by quorum sensing.

3. Overview of cell organisation into
tissue
 Cell adhesion molecules(CAMs)
 CAMs are adhesion protein of plasma membrane.
 CAMs are receptors composed of 3 domains .
i. Intracellular part interacts with cytoskelton
ii. Transmembrane imbedded in membrane
iii. Extracellular part interacts with other CAMs
 CAMs are mainly four types
1. Cadherins
2. Integrins
3. Selectins
4. Immunoglobulin(Ig) superfamily
 Extracellular matrix(ECMs)
 ECMs can be structural and fibrous proteins .glycoproteins found in
extacellular part of tissue.
 Main ECMs are –Collagen ,Elastin ,glucosaminoglycans,laminin and
fibronectins.

4. CAMs(continew)
CAMs
Ca+ Cell interaction
Depende
nt
Independen
t
 Cadherins
 Integrins

Selectins
o Ig
superfamil
y
Homophilic Heterophi
lic
Cadherins
Ig superfamily
 Selectins
Integrins
Ig superfamily

5.  Cadherins
 Cadherins are large family of glycoprotein.
 Have single transmembrane portion.
 Present in all multicellular and in some unicellular
organism.
 Extracellular part have 5 repeating domains.
 Tramsmit signal from ECM to cytoplasn.
 Cytosolic part associated with Catenin family of
cytosolic protein.
 E cadherins present on epithelial cell.
 N cadherins present on nerve,muscle&lens.
 P cadherins found on placenta & epidermis.

6.  Selectins
 Single transmembrane protein with conserved
Lectins domain that binds to the specific
oligosaccheride present on glycoprotein and
glycolipid of another cell surface.
 Selectins are cell-surface corbohydrate binding
proteins Lectins.
 Ca+ dependent .
 Large extracellular segment.
 Heterotypic binding.
 L –Selectins are found on suface of
leucocytes(WBC),E-selectins on Endothelial cells.

7.  Integrins
 Family of membrane proteins,Ca+ dependent.
 Heterotypic binding with non-covalent.
 Link Actin cytoskelton with various external structure.
 Cytoplasmic domain has Vinculin &alpha Actinin
adopter proteins that help to interacts integrins with
actin cytoskelton,extracellular domains binds with
Collagen fibers.
 Talin-here talin protein seprates both alpha and beta
subunit so integrins activate.
 RGD sequence-generally integrins recognise the
RGD sequence present on adhesive proteins
ligands.Ex-Fibronectins and Vitronectins.It also
recognise non-RGD sequence adhesive proteins
ligands,Ex-collagen ,laminin ,ICAM-1.

8. ICAMs
 Heterophilic and homophilic both type of binding.
 Ca+ independent.
 Cheif endothelial cell proteins that recognised by
WBC integrins are called ICAMs(intacellular cell
adhesion molecules) and VCAMs(vascular cell
adhesion molecules).
 Found antibody character,involved in immune
function.
 In human mutation in L1 gene babies birth with
Hydrocephalous disease characterised by water
in brain.

9. Extracellular Matrix(ECM)
• Tissue are made up of cells .they also contains a
remarkable complex intricate network of
macromolecules consisting ECMs.
• ECMs composition proteins +polysaccheride
• ECMs functions as provide support and anchorage for
shape of the cell.
• Basal lamila-thin layer of specialized ECM that lies
beneath all epithelial cells.
• ECM are divided –
o Glycosaminoglycans(GAGs)-charged polyccharides.
o Collagen and Elastins-fibrous proteins.
o Non collagen glycoprotein(Large class)-aspargine
linked polysaccherides.

10. GAGs
 GAGs are unbranched polysaccheride chains
composed of repeating unit of disaccheride.
 Repeating disaccheride is always an amino sugar
,which is in most of the cases sulfated.
 They are most anionic molecule produced by
animals and highly negatively charged.
 Hyaluronan is a simplest of GAGs,not attached
with protein(not a proteoglycans).
 The other GAGs attached with protein part and
known as proteoglycans such as sulphated
proteoglycans ,Chondrin sulphte ,heparin
sulphate and Keratin sulphate.

11. Collagen[fibrous protein]
 Most abundant fibrous protein found in
multicellular animal in connective tissue.
 Triple helical structure with three alpha chains
wrapped around one another in rope like
structure.
 Rich in proleine and glycine amino acid.
 Have glycine-x-y
repeates.(x=proleine,y=hydroxyproleine or
hydroxyglycine)
 Vitamin c( ascarbate) as a cofactor required for
hydroxylation of collagen .
 Dificiency of cofactor cause a disease in humans
name as Scurvy.

12. Elastin[fibrous protein]
 Responsible for elasticity and streching to
prevent tissue from tearing.
 Found(required )in skin ,blood vessels and lungs .
 Elastin fibres atleast 5 times more extensible than
a rubber bands.
 Most (main) component of elastin fiber is elastin
protein (highly hydrophobic)
 Rich in prolein and glycine amino acids similar to
collagen.

13. Laminin [glycoprotein]
 Adhesive protein
 Heterotrimeric matrix glycoprotein.
 Atleast 16 laminin isoform found in vertebrate.
 Laminin all three chain (alpha ,beta,gamma) are
covalently linked by several disulphide bonds.
 Basement membrane(basal lamila) hald the
laminin glycoprotein.

14. Fibronectin[glycoprotein]
 Fibronectin is a multiple domain glycoprotein
found in ECM.
 Important for cell-matrix interaction.
 20 isoform are generated of fibronectin by
alternating splicing of RNA transcript produced
from a single gene.
 For binding of integrins fibronectins have found
RGD sequence (motif).
 Fibronectin is adimer ,two very large subunits
joined by disulphide bonds at their c terminal
ends .
 Another ECM named Vibronectin binds to