Cell Types and Subcellular Structures

Lecture 5 of 4BBY1030 Cell Biology & Neuroscience

Institute: Psychology, Psychiatry and Neuroscience

Lecturer: Dr. Clemens Kiecker

Learning Outcomes

• Explain cell-cell adhesion.
• Explain cell-matrix adhesion.
• Describe the composition of the extracellular matrix.

Chapter 1: Extracellular Matrix (ECM)

Types of Extracellular Matrix

• Epithelium: Tightly packed cells binding to each other.
• Mesenchyme: Sparse cells.

Basement Membrane/Basal Lamina

• 2D sheet on which epithelial cells reside.
• Main components include Collagen IV, Laminin, Nidogen, and Perlecan.

Fibrillar Matrix

• 3D matrix composed of various fibers.
• Main components include Collagen I, Fibronectin, Elastin, and Proteoglycans.

Chapter 2: Cell Adhesion and Junctions

Types of Junctional Complexes

• Tight Junction
• Adherens Junction
• Desmosome
• Gap Junction
• Hemidesmosome
• Focal Adhesion

Desmosomes and Hemidesmosomes

• Linked to intermediate filaments providing structural support against mechanical stress.
• Desmosomes are found at cell-cell contacts; Hemidesmosomes are at cell-ECM interfaces.

Tight Junctions

• Surround the apical surface of epithelial cells, turning epithelia into barriers.
• Claudin is a key factor; knockout studies show its role in preventing water loss.

Gap Junctions

• Allow small molecules and ions to pass between cells, enabling chemical and electrical coupling.

Adherens Junctions

• Linked to the actin cytoskeleton and involved in mediating contractile forces for bending epithelia.

Focal Adhesions

• Link the actin cytoskeleton to the ECM.
• Form transiently during cell movement.

Discovery of Cell Adhesion Molecules

• Masatoshi Takeichi: Key figure in studying cadherins, which are calcium-dependent adhesion molecules.

Additional Types of Junctions Not Covered

• Selectin-based adhesion: Involved in leukocyte rolling.
• Neuronal synapse
• Plasmodesma: Plant gap junction equivalent.
• Septate Junctions: Invertebrate tight junctions.

Cancer Metastasis

• Linked intricately to cell adhesion processes.

Contact: Dr. Clemens Kiecker - [email protected]

Kings College London. All rights reserved.

End of Lecture