3. CELL - CELL INTERACTION
• Varying degree of interaction found in body
• 2 types:- Stable ( in tissue)
Transient ( in immune response)
IMPORTANCE
• Bidirectional transfer of information between exterior and interior
of cell
• Development and functioning of multicellular organism
• In tissue formation
5. Types
4 types of cell adhesion molecules
1) Selectin
2)Cadherins
3)Ig like cell adhesion molecules
4)Integrin
6.
7. Selectin
• Family of integral membrane glycoprotein
• Which bind with particular arrangement of sugar which project
from surface of other cell
• Calcium dependent adhesion
STRUCTURE
• Small cytoplasmic domain
• Membrane spanning domain
• Large extracellular domain ,in which outer most domain act as
lectin
9. Role
• Attachment of mammalian embryos to the wall of uterus
during implantation
• Selectin mediate transient interaction between circulating
leukocytes and vessels wall at site of inflammation and
clotting
10. Cadherin
• Large family of glycoprotein
• Calcium dependent adhesion
• It transmit signal from extracellular membrane to cytoplasm
• Homophilic interaction
Types
• 30 types of cadherins are known
1. E= epithelial
2. P= placental
3. N=neural
4. R= retinal
Brain express largest number of cadherins
11. Structure
• Integral membrane glycoprotein which made up from 720-750
amino acids
• Large extracellular segment which have 5 or 6 domain which have
same size and structure
• Single transmembrane domain
• Small cytosolic domain which attached with catenin family of
cytosolic protein
Role of catenin
• Tether the cadherin to cytoskeleton
• Signal transmission to cytoplasm
14. Ig like CAM
• It consist polypeptide chain which composed of number of
similar domain
• Each domain contain 70-110 amino acids which organised into
tightly folded structure
• It present on wide variety of protein called “immunoglobin
superfamily”
• Members of Ig superfamily are involve in immune function
• It mediate calcium independent cell - cell interaction
• Weak adhesion & homophilic & heterophilic interaction
15.
16. Example
1. NCAM = Neural cell adhesion molecule (CD56)
chromosome 11 , expressed on surface of neurons and skeletal
muscles . It also detect on Tc cell and dendritic cell
2. VCAM =Vascular cell adhesion molecules (CD106)
chromosome 1 , mediate adhesion of lymphocytes , monocytes ,
eosinophils , basophils to vascular endothelium
3. L1 cell adhesion molecule
Role: nervous system development ,neuronal migration and
differentiation
17. Importance of L1 in Human
• L1 syndrome is an inherited, X linked disorder occurring in male
that primarily affect the nervous system
• Mainly characterized by hydrocephalus, muscles stiffness &
difficulty in speaking
• It is generally observed in 1 in 30000 males
18. Integrin
• Calcium dependent adhesion
• Large family of integral membrane proteins which found only in
animals
• Large class of cell surface receptors
• Two major types of activities:
1. adhesion of cells to their substratum
2. transmission of signals from the external environment to the
cells interior ( outside –in)
19. Structure
• Heterodimer of alpha and beta subunit and they are non
covalently linked with each other
• In mammals ,29 integrin are known
1. 18 alpha subunit
2. 8 beta subunit
• Different combination of these alpha and beta subunit form
all 29 integrin molecules
20. • Two subunit are oriented to
form Globular extracellular
head & Pair of elongated legs
• The legs of each subunit
extend through membrane as
a single transmembrane helix
• End in small cytoplasmic
domain of about 20-70 amino
acids
21. • Beta 2 integrin mainly mediate cell – cell interaction , it bind
with specific ligand on another cell such as endothelial cell
sometimes it may be Ig superfamily.
• It enable WBC to attach firmly to endothelial cell at site of
infection & migrate out of the blood stream to the infected site
• human with genetic disease called leucocytes deficiency are
unable to synthesized beta 2 subunit
• Their WBC lack the beta 2 receptor & suffer with repeated
bacterial infection