The structural integrity of epithelial tissues is maintained primarily by:
Epithelial barrier maintenance depends on keratin-based intermediate filament network that spans cytoplasm from perinuclear region to desmosomes connecting adjacent cells and hemidesmosomes anchoring basal cells to underlying basement membrane via integrin alpha6beta4. Keratins K5/K14 heterodimers in stratified epithelia and K8/K18 in simple epithelia polymerize into tonofilaments bundled by plectin and desmoplakin, providing high tensile strength resisting mechanical rupture during stretch, compression and abrasion. Phosphorylation by PKC and p38 under stress increases solubility to allow remodeling during wound healing. While actin concentrated at adherens junctions supports adhesion and contractility via myosin II, and microtubules direct vesicular traffic to apical surfaces, neither provides long-term load bearing like intermediate filaments. Genetic evidence shows missense keratin mutations cause epidermolysis bullosa simplex with cytolysis upon mild trauma, whereas keratin knockout mice display tissue frailty. Therefore intermediate filaments serve as principal determinants of epithelial structural integrity through junction-linked networks. Integration with cell cycle kinases, calcium signaling and mechanical cues ensures coordinated remodeling during growth, migration and differentiation.
Ref: Fuchs Annu Rev Biochem; keratin IF at desmosomes hemidesmosomes provides epithelial mechanical resilience.