What is the Difference Between Tight Junction and Adherens Junction

The key difference tight junction and adherens junction is that tight junction is a type of cell junction that joins the plasma membranes of neighbouring cells together, while adherens junction is a type of cell junction that joins the actin filaments of neighbouring cells together.

Cell junctions are cellular structures containing multiple protein complexes that provide contact between neighbouring cells or a cell and the extracellular matrix in animals. These cell junctions are abundantly found in epithelial cells. In vertebrates, there are three types of cell junctions: anchoring junctions (adherens junctions, desmosomes, hemidesmosomes), gap junctions, and tight junctions.

CONTENTS

1. Overview and Key Difference
2. What is a Tight Junction 
3. What is an Adherens Junction
4. Similarities – Tight Junction and Adherens Junction
5. Tight Junction vs Adherens Junction in Tabular Form
6. Summary – Tight Junction vs Adherens Junction

What is a Tight Junction?

A tight junction is a type of cell junction in vertebrates that joins the plasma membranes of neighboring cells together. Tight junctions are found in the epithelial tissue of vertebrates. They normally act as barriers that regulate the movement of water and solutes between the epithelial layers. It is also classified as a paracellular barrier. The movement of solutes through a tight junction is largely dependent on size and charge. However, physiological pH plays a vital role in the selectivity of solutes passing through tight junctions. This is because most tight junctions are slightly selective for cations. Therefore, tight junctions present in different types of epithelia are selective for solutes of differing size, charge, and polarity.

There are approximately 40 proteins involved in tight junctions. These proteins are classified into four major types: scaffolding proteins, signaling proteins, regulation proteins, and transmembrane proteins. The roles of scaffolding proteins include organizing the transmembrane proteins and coupling transmembrane proteins to other cytoplasmic proteins and to actin filaments. The roles of signaling protein are helping in junction assembly, barrier regulation, and gene transcription. Regulation proteins regulate membrane vesicle targeting. Moreover, transmembrane proteins include junctional adhesion molecules, occludin, and claudin. It is believed claudin is the protein in the tight junction that is responsible for selective permeability.

What is an Adherens Junction?

Adherens junction is a type of cell junction that joins the actin filaments of neighboring cells together. It is also known as zonula adherens, intermediate junction, or belt desmosome. Adherens Junction is a protein complex that occurs at cell-cell junctions and cell-matrix junctions in epithelial and endothelial tissues. They are normally basal than tight junctions.

Adherens junction is a type of cell junction whose cytoplasmic face is linked to the actin cytoskeleton. It appears as a band encircling the cell or as a spot of attachment to the extracellular matrix. Furthermore, adherens junctions are composed of cadherins, p120, γ-catenin, and α-catenin.

What are the Similarities Between Tight Junction and Adherens Junction?

• Tight junctions and adherens junctions are two types of cell junctions found in vertebrates.
• Both junctions are made up of protein complexes.
• They are present in epithelial cells.
• Both are cell-cell junctions.
• They are very important in cell communication.

What is the Difference Between Tight Junction and Adherens Junction?

A tight junction is a type of cell junction joining the plasma membranes of neighboring cells together, while an adherens junction is a type of cell junction joining the actin filaments of neighboring cells together. Thus, this is the key difference between tight junction and adherens junction. Furthermore, a tight junction has proteins such as scaffolding protein, signaling protein, regulation protein, and transmembrane protein (adhesion molecule, occludin, and claudin). On the other hand, the adherens junction has proteins such as cadherins, p120, γ-catenin, and α-catenin.

The below infographic presents the differences between tight junction and adherens junction in tabular form for side-by-side comparison.

Summary – Tight Junction vs Adherens Junction

Cell junctions are cellular structures with multiple protein complexes that provide contact between neighboring cells or a cell and the extracellular matrix in animals. Tight junctions and adherens junctions are two types of cell junctions in vertebrates. A tight junction joins the plasma membranes of neighboring cells together, while an adherens junction joins the actin filaments of neighboring cells together. So, this is the key difference between tight junction and adherens junction.

Reference:

1. Harris, Tony J. C., and Ulrich Tepass. “Adherens Junctions: From Molecules to Morphogenesis.” Nature News, Nature Publishing Group.
2. “Tight Junction.” An Overview | ScienceDirect Topics.

Image Courtesy:

1. “Tight junction 03 CA” By Kuebi = Armin Kübelbeck. Translated to Catalan by Amadalvarez – own work, inspired by Hawkins BT, Davis TP: The blood-brain barrier/neurovascular unit in health and disease. Pharmacol Rev. 2005 Jun;57(2):173-85. PMID 15914466, and M. A. Deli: Potential use of tight junction modulators to reversibly open membranous barriers and improve drug delivery. Biochimica et Biophysica Acta, 2008, PMID 18983815 (CC BY 3.0) via Commons Wikimedia
2. “Adherens Junctions structural proteins gl” By Adherens Junctions structural proteins.SVG: LadyofHats (Mariana Ruiz)derivative work: Miguelferig – (CC0) via Commons Wikimedia