Connexon

Connexon

A connexon (also known as a connexin hemichannel or gap junction channel) is an assembly of six proteins, called connexins, that form a channel through the cell membrane. These channels allow for direct communication between the cytoplasm of adjacent cells, without the need for a signal to cross the extracellular space. This type of cell-cell communication is known as gap junction communication.

Structure

Each connexon is composed of six connexin proteins. These proteins are arranged in a circular fashion, creating a pore through the cell membrane. The connexin proteins themselves are four-pass transmembrane proteins, meaning they cross the cell membrane four times. The connexin proteins are named according to their molecular weight. For example, connexin 43 (Cx43) has a molecular weight of approximately 43 kilodaltons.

Function

Connexons form channels that allow for the direct transfer of small molecules and ions between cells. This includes molecules such as calcium ions, cyclic AMP, and inositol trisphosphate. These molecules are important for cell signaling and coordination of cellular activities.

Connexons can function in two ways: either as a hemichannel, allowing communication between the cell and the extracellular environment, or as a gap junction channel, allowing communication between two adjacent cells. When two connexons from adjacent cells align, they form a gap junction channel.

Clinical significance

Mutations in connexin genes can lead to a variety of diseases, known as gap junction diseases. These include skin disorders, deafness, cataracts, and cardiac abnormalities. For example, mutations in the gene for connexin 26 (Cx26) can lead to nonsyndromic deafness.

See also

• Gap junction
• Cell membrane
• Cell signaling

References

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