gap junction hemi-channel activity

Definition

Target type: molecularfunction

A wide pore channel activity that enables the transport of a solute across a membrane via a gap junction hemi-channel. Two gap junction hemi-channels coupled together form a complete gap junction. [GOC:dgh]

Gap junction hemi-channels, also known as connexons, are half-channels formed by the assembly of six connexin proteins. These channels span the plasma membrane of a single cell and act as a conduit for the direct transfer of ions, small molecules, and signaling molecules between adjacent cells. The molecular function of gap junction hemi-channel activity can be described as follows:

1. **Channel Formation:** Six connexin proteins assemble to form a hexameric structure, creating a hydrophilic pore through the cell membrane. This pore, known as the hemi-channel, is the functional unit of a gap junction.
2. **Gating and Permeability:** Hemi-channels are not always open. They are regulated by a variety of factors, including voltage, pH, intracellular calcium levels, and phosphorylation. When open, the pore allows the passage of molecules up to about 1 kDa in size, including ions, nucleotides, amino acids, second messengers, and signaling molecules.
3. **Intercellular Communication:** Two hemi-channels, one from each adjacent cell, align to form a complete gap junction channel. This allows for direct communication between the cytoplasm of the two cells, enabling the rapid exchange of ions and signaling molecules.
4. **Tissue Coordination:** Gap junction communication plays a crucial role in coordinating the activity of cells within tissues and organs. This includes functions such as:
- **Electrical Coupling:** The rapid spread of electrical signals between cells, enabling synchronized activity in tissues like heart muscle and smooth muscle.
- **Metabolic Coupling:** The exchange of metabolites and nutrients between cells, ensuring optimal function and coordination.
- **Developmental Signaling:** The communication of developmental signals between cells, contributing to tissue morphogenesis and differentiation.
5. **Regulation of Cell Function:** Gap junction communication can also regulate cell function by:
- **Modulating Cell Growth and Differentiation:** Gap junctions can influence cell growth and differentiation by transmitting growth factors and other signaling molecules.
- **Controlling Cell Death:** Gap junctions can contribute to the regulation of apoptosis and other forms of cell death.
6. **Pathological Roles:** Dysregulation of gap junction activity has been implicated in a number of pathological conditions, including:
- **Cardiovascular Disease:** Defects in gap junction communication can disrupt heart rhythm and contribute to heart failure.
- **Neurological Disorders:** Impaired gap junction function has been linked to epilepsy, Alzheimer's disease, and other neurological disorders.
- **Cancer:** Alterations in gap junction communication can promote tumor growth and metastasis.

In summary, gap junction hemi-channel activity is essential for intercellular communication and the coordination of cell function in various tissues and organs. Their ability to regulate ion flow, signaling molecule exchange, and electrical coupling plays a vital role in normal physiological processes and contributes to the development and progression of a variety of diseases.'
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Proteins (2)

Compounds (2)