Intercellular Junction

Presented By: 14-ARID-2022 FAISAL SHAHZAD SOMROO

Presented To: Dr. Riaz Hussain Pasha

Intercellular junctions

• A cell junction is a type of structure that exists within the tissue of some multicellular organisms.

• specializations of the cellular margins that contribute to the adhesion or allow for communication between cells.

• Mostly found in epithelial tissues.

CONT…

There are three main types:• Gap junction (nexus).

• Tight junction (zonula occludens)• Anchoring junction -Desmosome (macula adherens)

-Hemidesmosome -Adheren (zonula adherens)

Gap Junction:

• It is a communicating junction.

• Gap junctions consist of intercellular channels in the plasma membrane of adjacent cells.

• Consist of six connexon proteins arranged to form a doughnut shape structure.

• Play role in cardiac muscle contraction.

Cont…

• Helps in signal transfer in brain.

• Their size vary in different cells.

Tight Junction:

• The borders of two cells are fused together, often around the whole perimeter of each cell, forming a continuous belt like junction known as a tight junction or zonula occludens (zonula = latin for belt). 

• ZO-1 & ZO-2 Link transmembrane proteins (Occludin and Clauding) with Spectrin.

• Prevent leakage of fluid.

• Found in the apical region around the cell's circumference.

Cont…

• It prevent mobility of transmembrane proteins.

• It regulate the movement of water and solutes between epithelial layer.

• Lines the gastrointestinal tract.

Anchoring Junction:

• Cells within tissues anchor to one another and to extracellular fluid.

• There are following three types:

1. Desmosomes Junction2. Hemidesmosomes Junction3. Adherens Juntion

Cont..

Junction Cytoskeletal Anchor

Transmembrane Linker

Ties cell to

Desmosomes Intermediate Filaments

Cadherin Cell

Hemidesmosome

Intermediate Filaments

Integrins ECF

Adherens Junction

Actin Filaments

Cadherin/Integrins

Cell/ECF

Desmosomes:

• Form cell to cell junction.

• Known as Maculae adherens.

• Intracellular adaptor proteins connect to intermediate filament and form cytoplasmic plaque.

• Cadherin joins the cytoplasmic plaques of two cells.

Cont…

• The gap b/w this junction is 30nm

• Found in epidermis of skin and muscle tissues.

• Blistering diseases.

• Pemphigus.

• Hailey-Hailey disease.

Hemidesmosomes:

• Connect cell to extracellular fluid.

• Connect epithelial cells to basement membrane.

• Integrins are the linking proteins.

• Present in epidermis of skin.

• Epidermolysis bullosa.

Adheren Junction:

• Junctions which form junction b/w cell to cell.

• Also known as Zonulae adherens.

• Lies basal to tight junction.

• Microfilaments of two cells are connected by cadherins.

• Cytoplasmic face is linked to actin cytoskeleton.

• Actin myosin interaction can change the shape of the epithelium.