cellular hyperosmotic response

Definition

Target type: biologicalprocess

Any process that results in a change in state or activity of a cell (in terms of movement, secretion, enzyme production, gene expression, etc.) as a result of detection of, or exposure to, a hyperosmotic environment, i.e. an environment with a higher concentration of solutes than the organism or cell. [GOC:mah]

Cellular hyperosmotic response is a complex biological process that occurs when cells are exposed to a hypertonic environment, meaning the external solute concentration is higher than the internal concentration. This leads to a net movement of water out of the cell, causing cellular shrinkage and potential damage. Cells have evolved a variety of mechanisms to cope with hyperosmotic stress, aiming to maintain cell volume and protect cellular integrity. These mechanisms include:

1. **Osmolyte Accumulation:** Cells actively transport organic osmolytes, such as amino acids (e.g., taurine), sugars (e.g., trehalose), and polyols (e.g., sorbitol), into the cytoplasm. These osmolytes increase the intracellular solute concentration, counteracting the osmotic gradient and drawing water back into the cell.

2. **Ion Transport:** Cells can regulate the influx and efflux of ions, particularly potassium and chloride, to adjust intracellular osmotic pressure. For instance, increased potassium uptake or chloride efflux can contribute to water retention.

3. **Aquaporin Regulation:** Aquaporins are water channel proteins embedded in the cell membrane that facilitate water movement across the cell membrane. In response to hyperosmotic stress, cells can regulate the expression or activity of aquaporins to adjust water permeability.

4. **Macromolecular Synthesis:** Some cells respond to hyperosmotic stress by increasing the synthesis of specific macromolecules, such as heat shock proteins, which contribute to stress tolerance.

5. **Stress-Activated Signaling Pathways:** Hyperosmotic stress triggers various signaling pathways, including the mitogen-activated protein kinase (MAPK) pathway and the phosphoinositide 3-kinase (PI3K) pathway. These pathways activate downstream targets involved in osmolyte accumulation, ion transport, and gene expression.

6. **Cell Wall Modifications:** In plant cells, hyperosmotic stress can induce changes in cell wall composition and structure, contributing to osmotic regulation.

7. **Adaptive Remodeling:** Prolonged hyperosmotic stress can lead to long-term adaptations, including changes in cell morphology, gene expression, and metabolic pathways, to enhance stress tolerance.

The specific response mechanisms and their activation levels depend on the severity and duration of hyperosmotic stress, as well as the cell type and organism. Understanding cellular hyperosmotic response is crucial for understanding various physiological processes, such as water balance, cell volume regulation, and stress adaptation. It also has implications for various diseases, including diabetes, kidney disease, and neurological disorders.'
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Proteins (6)

Compounds (95)