gap junction-mediated intercellular transport

Definition

Target type: biologicalprocess

The movement of substances between cells via gap junctions. A gap junction is a fine cytoplasmic channel, found in animal cells, that connects the cytoplasm of one cell to that of an adjacent cell, allowing ions and other molecules to pass freely between the two cells. [GOC:hjd, PMID:14506308, PMID:23261543, Wikipedia:Gap_junction]

Gap junctions are specialized intercellular channels that directly connect the cytoplasm of adjacent cells, allowing for the passage of small molecules and ions. This process, known as gap junction-mediated intercellular transport, plays a critical role in various physiological functions.

The formation of gap junctions begins with the synthesis of connexins, transmembrane proteins that assemble into hexameric structures called connexons. Two connexons from adjacent cells align and dock to form a channel, which spans the intercellular space. This channel allows for the bidirectional exchange of molecules between the connected cells.

The size and charge selectivity of gap junctions is determined by the specific connexin isoforms expressed. Generally, gap junctions allow the passage of molecules with a molecular weight less than 1 kDa, including ions, second messengers, metabolites, and signaling molecules. However, larger molecules, such as proteins and nucleic acids, are typically excluded.

Gap junction-mediated intercellular transport is crucial for various cellular processes, including:

- **Coordination of cell activity**: Gap junctions enable the rapid and synchronized communication between cells, facilitating coordinated responses to stimuli. This is essential for processes like heart muscle contraction, smooth muscle contraction, and neuronal signaling.
- **Metabolic coupling**: Gap junctions allow for the exchange of nutrients and metabolites between cells, ensuring the efficient distribution of resources.
- **Development and tissue organization**: Gap junctions play a role in cell differentiation, proliferation, and tissue morphogenesis by facilitating cell-to-cell communication during development.
- **Homeostasis**: Gap junctions contribute to maintaining cellular homeostasis by allowing for the exchange of ions and other signaling molecules, regulating cell volume, and responding to environmental changes.

The regulation of gap junction permeability is essential for proper cellular function. Several factors can influence the opening and closing of gap junctions, including:

- **Voltage**: Changes in membrane potential can affect the permeability of gap junctions.
- **pH**: Fluctuations in intracellular pH can influence gap junction conductance.
- **Calcium concentration**: Increased intracellular calcium levels can lead to the closure of gap junctions.
- **Phosphorylation**: The phosphorylation state of connexins can regulate gap junction permeability.
- **Other signaling molecules**: Various signaling molecules, such as nitric oxide and cyclic AMP, can influence gap junction function.

Dysfunction of gap junctions can contribute to various diseases, including:

- **Cardiovascular diseases**: Impaired gap junction function can lead to arrhythmias and heart failure.
- **Neurological disorders**: Defects in gap junctions have been implicated in epilepsy, Alzheimer's disease, and Parkinson's disease.
- **Cancer**: Abnormal gap junction communication can promote tumor growth and metastasis.

In summary, gap junction-mediated intercellular transport is a critical process that enables the direct communication and exchange of molecules between adjacent cells. This process plays a vital role in various physiological functions, including cell coordination, metabolic coupling, development, and homeostasis. Dysregulation of gap junction function can contribute to various diseases.'
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