maintenance of epithelial cell apical/basal polarity

Definition

Target type: biologicalprocess

The maintenance of the apicobasal polarity of an epithelial cell. [GOC:bf]

Epithelial cell apical/basal polarity is a fundamental feature of epithelial tissues, essential for their barrier function, selective transport, and proper tissue organization. This polarity is established and maintained through complex molecular mechanisms that involve a dynamic interplay of proteins, lipids, and cytoskeletal components.

The apical domain faces the lumen or external environment, while the basal domain interacts with the underlying basement membrane and supporting cells. This distinct polarization is characterized by the asymmetric distribution of membrane proteins, lipids, and cytoskeletal elements.

**Establishment of Apical-Basal Polarity:**

* **Cell-cell adhesion:** Tight junctions (TJs) are critical for establishing and maintaining apical-basal polarity. They form a continuous seal between adjacent cells, segregating apical and basolateral domains.
* **Paracellular transport:** TJs control the passage of molecules through the intercellular space, contributing to the selective permeability of the epithelium.
* **Basolateral anchoring:** Adherens junctions (AJs) connect cells to the underlying basement membrane, providing structural support and anchoring the basolateral domain.
* **Polarized protein trafficking:** The delivery of proteins to the correct membrane domains is essential for polarity. This is achieved through a complex network of intracellular trafficking pathways.

**Maintenance of Apical-Basal Polarity:**

* **Polarized recycling:** Membrane proteins are constantly recycled between apical and basolateral domains, maintaining their correct distribution.
* **Signaling pathways:** Several signaling pathways, including the Wnt, Hippo, and PI3K pathways, regulate the establishment and maintenance of epithelial polarity.
* **Cytoskeletal dynamics:** The actin and microtubule cytoskeletons play crucial roles in polarizing the cell, maintaining cell shape, and organizing the apical and basolateral domains.
* **Lipid asymmetry:** Differences in lipid composition between the apical and basolateral membranes contribute to the establishment and maintenance of polarity.

**Consequences of Polarity Loss:**

* **Barrier defects:** Loss of apical-basal polarity can lead to impaired barrier function, allowing leakage of fluids and pathogens.
* **Transport defects:** Disrupted polarity can affect the selective transport of molecules across epithelial tissues.
* **Tissue dysmorphogenesis:** Abnormal polarity can contribute to the development of epithelial pathologies, including cancer.

In conclusion, the maintenance of epithelial cell apical/basal polarity is a dynamic and tightly regulated process involving a complex interplay of molecular mechanisms. This polarity is essential for the proper function and integrity of epithelial tissues, playing a critical role in maintaining tissue homeostasis and protecting the organism from the external environment.'
"

Proteins (1)

Compounds (1)