Expression of class II molecules by B cells is down-regulated by IFN-¥. 

TLS Online TPP Program

#Id: 10065

#Unit 4. Cell Communication and Cell Signaling

Two type of Cadherins:

1. Classical cadherin proteins

2. Nonclassical cadherin proteins

TLS Online TPP Program

#Id: 10066

#Unit 4. Cell Communication and Cell Signaling

Extracellular region of a classical cadherin contains five copies of the cadherin domain separated by flexible hinge regions

TLS Online TPP Program

#Id: 10067

#Unit 4. Cell Communication and Cell Signaling

Ca2+ ions bind to sites near each hinge and prevent it

from flexing, so that the whole string of cadherin domains behaves as a rigid and slightly curved rod to generate cell–cell adhesion

TLS Online TPP Program

#Id: 10068

#Unit 4. Cell Communication and Cell Signaling

In absence of Ca2+, 

the hinges can flex, the structure becomes floppy & adhesion fails

TLS Online TPP Program

#Id: 10069

#Unit 4. Cell Communication and Cell Signaling

Each classical cadherin molecule contains: 

A single TM domain

A short C-terminal cytosolic domain

Five extracellular “cadherin” domains (EC1–EC5)

TLS Online TPP Program

#Id: 10070

#Unit 4. Cell Communication and Cell Signaling

Three classes of classical cadherins: 

E-cadherin -present on epithelial cells

N-cadherin - present on nerve, muscle and lens cells

P-cadherin - present on cells in the placenta & epidermis