gap junction assembly

Definition

Target type: biologicalprocess

Assembly of gap junctions, which are found in most animal tissues, and serve as direct connections between the cytoplasms of adjacent cells. They provide open channels through the plasma membrane, allowing ions and small molecules (less than approximately a thousand daltons) to diffuse freely between neighboring cells, but preventing the passage of proteins and nucleic acids. [GOC:jid, ISBN:0716731363]

Gap junction assembly is a complex process that involves the coordinated interaction of multiple proteins to form intercellular channels between adjacent cells. These channels allow for the direct exchange of ions and small molecules, playing a critical role in cell-to-cell communication and tissue function. The assembly process can be broadly divided into several stages:

**1. Synthesis and Transport:**
* Gap junction proteins, primarily connexins, are synthesized in the endoplasmic reticulum (ER) as monomers.
* They are then transported to the Golgi apparatus for further processing and sorting.
* After modification in the Golgi, connexins are packaged into transport vesicles and move towards the plasma membrane.

**2. Plasma Membrane Targeting and Assembly:**
* At the plasma membrane, connexins associate with each other to form hexameric structures called connexons.
* Each connexon consists of six connexin subunits, arranged in a ring-like structure with a central pore.
* Two connexons, one from each opposing cell, align and dock with each other to form a complete gap junction channel.
* The docking process involves a specific interaction between the cytoplasmic loops of connexins from the two connexons.

**3. Channel Opening and Regulation:**
* Once formed, the gap junction channel can open or close in response to various stimuli, including changes in intracellular calcium levels, pH, and membrane potential.
* This regulation ensures that communication between cells is controlled and appropriate for the specific physiological context.

**4. Gap Junction Turnover and Degradation:**
* Gap junctions are dynamic structures that are constantly being assembled, disassembled, and recycled.
* This turnover is important for maintaining the integrity of the junction and for regulating intercellular communication.
* Gap junctions can be degraded through endocytosis, a process where the junction is internalized by the cell and eventually broken down by lysosomes.

**Factors Influencing Gap Junction Assembly:**
* **Cell type:** Different cell types express different connexins, leading to variations in gap junction properties and function.
* **Developmental stage:** Gap junction assembly is regulated during development and can be influenced by factors such as growth factors and hormones.
* **Pathological conditions:** Disruptions in gap junction assembly can contribute to various diseases, including heart disease, cancer, and neurodegenerative disorders.

**Overall, gap junction assembly is a highly regulated process that involves the interplay of multiple proteins, signaling pathways, and cellular processes. Understanding the mechanisms underlying gap junction formation and regulation is crucial for comprehending cell-to-cell communication and for developing therapeutic strategies for diseases associated with gap junction dysfunction.'
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Proteins (2)

Compounds (1)