Desmosomes & Tight Junctions

[blazinfury]

I was looking online but I cannot find a good resource that explains the difference b/w desmosomes and tight junctions and the rationale behind their respective locations in the body. It seems to me that they do nearly the same thing. Would someone please be able to clarify. Thank you.

[immortal]

Based on the Cell and Molecular Biology textbook I have tight junctions are specialized regions whose main function is to maintain a different environment between the inter-cellular space than that environment which exists outside that tissue i.e. only certain bio-molecules can enter into the cell and exit out of the cell with in a tissue and Desmosomes are of two types Spot and Belt Desomosomes and their main function is cell adhesion.

[Ringer]

To add to Immortal's post, desmosomes are proteins in the plasma membrane who function in cell adhesion as well as some types molecular adhesion. In reference to tight junctions desmosomes on both cellular membranes will interact, usually winding into each other, and create a very tight connection so that the membranes are basically joined. Depending on the cell type the junctions can have different functions but overall they work as a barrier.

[blazinfury]

Thank you both for the clarification. So basically tight junctions are more for preventing particles/proteins/compounds from entering the tissue, while desmosomes just hold cells together-- like squamous epithelial cells. My own research did not yield much clarification except the proteins that construct each of them. Desmosomes are composed of keratin while tight junctions are composed of 2 other proteins. I also found that desmosomes are founds in the heart and mutations in their function can lead to various heart arrhythmias Tight junctions are found in a majority of cells in out body like lining blood vessels and the stomach.

[Ringer]

So I realize that I skipped/mixed up a part in my explanation, I was half explaining a junctional complex. Let's try this again.

 

Tight junctions are a type of cell to cell junction that creates a selective barrier by sealing gaps between epithelial cells. So where ever there are epithelial cells there are tight junctions. The claudin and occludin proteins form a kind of puzzle that fit together at the regions of the cell that need to be sealed. This creates an extremely tight barrier directly at the transmembrane protein.

 

Desmosomes are cell to cell junctions that use cadherins to bind to intermediate filaments to mediate hydrophilic adhesion to other intermediate filaments. Individually they are much weaker than most other adhesions, but the amount of binding filaments gives the junction a lot of mechanical strength. I think they are mainly found in skin cells, but the protein family cadherins are freaking everywhere.

Edited March 18, 2013 by Ringer