CELL JUNCTIONS AND ADHESIONS

AMITHBABU.C.BMScD-ENDO

INTRODUCTION-CELL JUNCTION

What are cell junctions?

What are the three most common types of cell junctions?

INTRODUCTION-CELL JUNCTION

CELL JUNCTIONS

They are classified into 3 main groups1.Tight junctions2.Anchoring junction =adhesion belt , desmosome and hemidesmosome3.Gap junction

CELL JUNCTIONWhat do all adhesive

junctions have in common?

Where are adhesive junctions most commonly found?

Cell Junctions

What distinguishes a tight junction?

Where are tight junctions found?

CELL JUNCTION

What is special about gap junctions?

FUNCTIONAL CLASSIFICATION

Seal cells of an epithelial sheet to create a permeability barrier

Apical vs. Basolateral sortingMolecular Composition Claudin: Transmembrane Occludin: Transmembrane ZO Proteins: Plasma Membrane. Actin cytoskeleton attachment

TIGHT/OCCLUDING JUNCTIONS

(ZONULA OCCLUDENS)

ADHERENS JUNCTIONS

What are adherent junctions

DESMOSOMES

HEMIDESMOSOMES“HALF-DESMOSOMES”

Distribute forces on an epithelium to the basal lamina

Integrins mediate basal lamina adhesionAnchor proteins link integrins to

intermediate filaments via plectin

HEMIDESMOSOMES

De: DesmosomeHD: HemidesmosomeLD: Lamina Densa

GAP JUNCTIONSWhat are gap junctions ?

What are their functions?

COMMUNICATINGGAP JUNCTIONS

GAP JUNCTIONS

CELL ADHESION

What is cell adhesion?

FORMING THE CONNECTIONS BETWEENCELLS

Cell adhesion receptors enable cells to recognize and bind molecules on other cells or in the extracellular matrix

Ligands can be other cell adhesion receptors (receptor receptor contact) or extracellular matrix molecules Make cells stick to other cells or extracellular matrixCell adhesion receptors also activate intracellular

signalling pathways (primarily for cell death/survival but also secretion etc.)

CLASSIFICATION

Integrin familySelectin family Immunoglobulin (Ig) superfamilyCadherin family Mucin-like familyOther adhesion molecules

CELL ADHESIONWhat are the

different categories of adhesion receptors?

What is the difference between homophilic and heterophilic interactions?

CELL ADHESIONWhat characteristics do all CAMs

share?

In what kinds of adhesion events do the CAMs participate?

CELL ADHESION SUMMARY